Starts With A Bang podcast: Recent Episodes
Ethan Siegel
It's no secret that the Universe and the objects present within it, as we see them all today, have changed over time as the Universe has grown up over the past 13.8 billion years. Galaxies are larger, more massive, more evolved, and are richer in stars but fewer in number than they were back in the early stages of cosmic history. By looking farther and farther away, we can see the Universe as it was at earlier times, but we're going to be limited in many ways: by how deep our telescopes can see, by what wavelengths they're capable of seeing, and by what small fraction of the sky they're capable of observing.
That's why an observing program like COSMOS-Web, the largest, widest-field JWST observing program to date, is so important. It isn't just revealing galaxies as they are nearby (at late times), at a variety of intermediate distances (and earlier times), and at ultra-large distances (and the earliest times of all), but due to its wide-field nature, is revealing galaxy types of varying abundances: the common-type galaxies, galaxies that are representative of more uncommon varieties, and even significant numbers of rare galaxies. And it's this aspect of galaxy evolution that makes me so proud and lucky to welcome Dr. Olivia Cooper to the podcast.
Olivia is a recently-minted PhD who works as part of the COSMOS-Web team, specializing in galaxy evolution and using JWST data — along with data from other world-class observatories — to investigate how the galaxies in our Universe grew up, and what that can teach us about our own cosmic past. It truly is a banger of an episode that you'll want to listen to every minute of, so tune in and dive deep into the depths of the distant Universe on our latest adventure of the Starts With A Bang podcast!
(This image shows a tiny sliver of the COSMOS-Web survey, with galaxies at a variety of distances along with a portion of a rich cluster of galaxies, at right, of this image. Credit: ESA/Webb, NASA & CSA, G. Gozaliasl, A. Koekemoer, M. Franco, and the COSMOS-Web team)
It's hard to believe, but it was only back in the early 1990s that we discovered the very first planet orbiting a star other than our own Sun. Fast forward to the present day, here in 2025, and we're closing in on 6000 confirmed exoplanets, found and measured through multiple techinques: the transit method, the stellar wobble method, and even direct imaging. That last one is so profoundly exciting because it gives us hope that, someday soon, we might be able to take direct images of Earth-like worlds, some of which may even be inhabited.
Although it may be a long time before we can get an exoplanet image as high-resolution as even the ultra-distant "pale blue dot" photo that Voyager took of Earth so many decades ago, the fact remains that science is advancing rapidly, and things that seemed impossible mere decades ago now reflect today's reality. And the people driving this fascinating field forward the most are the mostly unheralded workhorses of the fields of physics and astronomy: the early-career researchers, like grad students and postdocs, who are just beginning to establish themselves as scientists.
In this fascinating conversation with Dr. Kielan Hoch of Space Telescope Science Institute, we take a long walk at the current frontiers of science and peek over the horizon: looking at the good, the bad, and the ugly of what we're facing here in 2025. It's a conversation that might make you hopeful, angry, and optimistic all at the same time. After all, it's your Universe too; don't you want to know what comes next?
(This composite image shows a brown dwarf star, center, with the first directly imaged exoplanet, 2M1207 b, in red alongside it. This image was acquired in 2004 by the Very Large Telescope in Chile, operated by the European Southern Observatory. In the years and decades since, dozens of more exoplanets have been directly imaged, with hundreds more expected in the next decade. Credit: ESO/VLT.)
Out there in the Universe, somewhere, a second example of an inhabit world or planet likely awaits us. It could be some other planet or moon within our own Solar System; it could be a spacefaring, interstellar civilization, or it could be an exoplanet around a different parent star. Although the search for life beyond Earth generally focuses on worlds that have similar conditions to Earth, like rocky planets with thin atmospheres and liquid water on their surfaces, that's not necessarily the only possibility. The truth is that we don't know what else is going to be out there, not until we look for ourselves and determine the answers.
And yet, if you've been paying attention to the news, you might think that super-Earth or mini-Neptune type worlds, such as the now-famous exoplanet K2-18b, might be excellent candidate planets for life. Some have even gone as far as to claim that this planet has surefire biosignatures on it, and that the evidence overwhelmingly favors the presence of life within this planet's atmosphere. But the science backing up that claim has been challenged by many, including our two podcast guests for this episode: Dr. Luis Welbanks and Dr. Matthew Nixon.
Beyond the breathless and sensational claims, what does the actual science concerning K2-18b in particular, and of biosignatures on exoplanets in general, actually teach us? What does the evidence indicate, and if we are going to find inhabited exoplanets, what will it take for us to actually announce a positive detection with confidence and less ambiguity? That's what this episode of the Starts With A Bang podcast is all about; I hope you enjoy it!
(When an exoplanet passes in front of its parent star, a portion of that starlight will filter through the exoplanet’s atmosphere, allowing us to break up that light into its constituent wavelengths and to characterize the atomic and molecular composition of the atmosphere. If the planet is inhabited, we may reveal unique biosignatures, but if the planet has either a thick, gas-rich envelope of volatile material around it, or alternatively no atmosphere at all, the prospects for habitability will be very low. Credit: NASA Ames/JPL-Caltech)
Perhaps the strongest evidence we've ever acquired in support of the Big Bang has been the discovery of the leftover radiation from its early, hot, dense state: today's cosmic microwave background, or CMB. While there were many competing ideas for our cosmic origins, only the Big Bang predicted a uniform, omnidirectional bath of blackbody radiation: exactly what the CMB is.
But it turns out the CMB encodes much more information than just our cosmic origins; it allows us to map the very early Universe from when it was just 380,000 years old, and gives us vital information about what has happened to light from that time over its 13.8 billion year journey to our eyes. It encodes information about our cosmic expansion history, about dark matter and dark energy, about intervening galaxy clusters, and about the material here in our own galaxy, along with much more. It is, arguably, the richest source of information from any one single observable in our entire Universe.
Here to guide us through what CMB scientists are working on here in 2025, including what we've learned and what we're still trying to find out, I'm so pleased to welcome Dr. Patricio Gallardo to the show. We've got more than an hour and a half of quality science to go through, and by the end, I bet you'll be more excited about the upcoming Simons Observatory, designed to measure the CMB to higher precision than ever before, than you knew you should be. Enjoy!
(This image shows the Large Aperture Telescope's colossal, 6-meter primary and secondary mirrors at the Simons Observatory in February of 2025. The telescope has already seen first light, and will soon begin delivering new CMB science as never before. Credit: M. Devlin/Simons Observatory)
When we search for life in the Universe, it makes sense to look for planets that are similar to Earth. To most of us, those signatures would look the same as the ones we'd see if we viewed our planet today: blue oceans, green-and-brown continents, polar icecaps, wispy white clouds, an atmosphere dominated by nitrogen and oxygen, and even the modern signs of human activity, such as increasing greenhouse gas emissions, planet modification, and electromagnetic signatures that belie our presence.
But for most of our planet's history, Earth was just as "inhabited" as it is today, even though it looked very different. One fascinating period in Earth's history that lasted approximately 300 million years resulted in a planet that looked extremely different from modern Earth: a Snowball Earth period, where the entire surface, from the poles to the equator, was completely covered in snow and ice. This isn't just speculation, but is backed up by a remarkable, large suite of observational and geological evidence.
So what was Earth like during this period? How did it fall into this phase, how did it remain trapped in that state for so long, and how did it finally thaw again? To help explore this topic, I'm so pleased to welcome PhD candidate Alia Wofford to the program, who conducts intricate climate models of early Earth to try to reproduce those early conditions. From that work, we're learning about what we should be looking for when it comes to potentially inhabited exoplanets, because Earth has been inhabited for around 4 billion years, and wow, has its appearance changed over all that time. Have a listen and see for yourself!
(This illustration shows a frozen-over planet, but one that still possesses a significant liquid ocean beneath the surface ice. Many worlds in our Solar System may be described by this scenario at various points in cosmic history, including even planet Earth more than two billion years ago. Credit: Pablo Carlos Budassi/Wikimedia Commons)
It might seem hard to fathom, but it hasn't even been ten full years since advanced LIGO, the gravitational wave observatories that brought us our very first successful direct detection, turned on for the very first time. In the time since, it's been joined by the Virgo and KAGRA detectors, and humanity is currently closing in on 300 confirmed gravitational wave detection events. What was an unconfirmed prediction of Einstein's General Relativity for a full century has now become one of the fastest-growing fields in all of astronomy and astrophysics.
Here in 2025, we're now looking forward to the LISA era: where we're going to build our first gravitational wave detectors in space. They'll have far longer baselines (i.e., separations between the various spacecrafts/stations) than any terrestrial gravitational wave detector, enabling us to detect fundamentally different classes (and masses) of objects that emit gravitational waves. At the same time, the rise of artificial intelligence and machine learning is enabling us to detect and characterize ever greater numbers of gravitational wave events, an incredibly exciting development.
For this episode of the Starts With A Bang podcast, I'm so pleased to welcome Shaniya Jarrett to the program. She's here to guide us up to the frontiers and help us peer over the horizon, and is currently an astronomy PhD student at the University of Maryland after earning her Masters degree from the Fisk-Vanderbilt bridge program. Have a listen and learn all of the exciting science that's not only within our reach today, but that we all have to look forward to in the very near future!
(The image above shows an illustration of the three future LISA, or Laser Interferometer Space Antennae, spacecrafts, in a trailing orbit behind the Earth. LISA will be our first space-based gravitational wave detector, sensitive to objects thousands of times as massive than the ones LIGO can detect. Credit: University of Florida/NASA)
Out there in the Universe, each star represents an opportunity: a chance for a stellar system to develop that just might possess something remarkable. While we normally think about life, and intelligent life at that, as the grand prize the Universe has to offer, there are a wide variety of fascinating phenomena that are out there to consider. Whereas Mercury, for example, is the closest world to our Sun in our own Solar System, it still takes 88 days to make a complete revolution. In other systems, however, exoplanets can be so hot that they orbit their parent star in less than a single Earth day.
In fact, we've discovered a few systems that are so extreme, the planets that orbit them are in the process of disintegrating: where the heat, winds, and radiation from the parent star actually blows part of the planet itself away. This doesn't just include a planet's atmosphere, which is what we see for giant worlds, but even the surfaces and interiors of rocky planets in the most extreme cases. At temperatures of around 2000 degrees and upwards, these exoplanets can lose their crusts, mantles, and even their cores over long enough timescales.
Believe it or not, we've actually caught a few exoplanets doing exactly this, and we've got the JWST spectra in hand for one of them now, teaching us, for the first time, what a planetary interior is made of outside of our own Solar System. I'm so pleased to have the first author from that 2025 study, soon-to-be Dr. Nick Tusay, as our guest on this edition of the Starts With A Bang podcast, as we take a look at the most extreme exoplanetary systems ever discovered!
(This image shows an illustration of an evaporating, rocky exoplanet, with an enormous dust tail arising from the material blown off of the planet from its interaction with the nearby star. Credit: NASA/JPL-Caltech)
Sure, it's easy to look out at the Universe and take stock of what we find. Although spiral and elliptical galaxies house the majority of the Universe's stars, represented locally by galaxies like Andromeda and our own Milky Way, the overwhelming majority of galaxies are much smaller and lower in mass than we and our cousins are. These low-mass galaxies, the dwarf galaxies in the Universe, represent upwards of 97% of all the galaxies that exist.
However, while most of the dwarf galaxies we know of are found as satellites around larger, more massive galaxies, they aren't good laboratories for helping us understand the Universe as it was long ago. Back during the first few billion years of cosmic history, it wasn't just dwarf galaxies that formed the majority of starlight in the cosmos, but isolated dwarf galaxies: dwarf galaxies that hadn't yet interacted with larger neighbors.
We can best understand those early-stage galaxies by studying their late-time analogues: isolated dwarf galaxies in the Universe today. On this edition of the Starts With A Bang podcast, I sit down with Dr. Catherine (Cat) Fielder, and we talk about some of the nearest, most isolated galaxies of all: including some that have been imaged with flagship-quality telescopes. What have we learned about them so far, and what else are we hoping to discover? Find out here, today!
(This three panel image shows a ground-based, wide field view of the entirety of galaxy NGC 300: one of the closest spiral galaxies outside of our Local Group. Though this galaxy is relatively isolated, there are dwarf galaxies nearby it that are even more isolated than this galaxy itself, making them excellent objects to teach us how tiny galaxies grow up in isolation from large, major galaxies. Credit: ESA/Hubble and NASA)
Out there in the Universe, there are tremendous, uncountable numbers of planetary systems just waiting to be discovered. But stellar systems won't just consist of planets orbiting a parent star; there will be moons, asteroids, Kuiper belt-like objects, and many of them will be bound together into their own rich sets of systems, with both irregular and round bodies comprising these planetary systems.
Here in our own Solar System, we have at least three notable large, terrestrial-sized bodies with impressive lunar systems of their own: the Earth-Moon system, the Mars-Phobos-Deimos system, and the Plutonian planetary system. Pluto, interestingly, is orbited by Charon, which is very large and massive compared to Pluto, an unusual and possibly unique, or most extreme, configuration of all known such bodies. But how did it get to be that way? That's the topic of this podcast, and the research focus of this month's guest: Dr. Adeene Denton.
It's kind of amazing what variety can emerge in terms of surviving systems from ancient planetary collisions, but by running simulations and understanding the geology of these worlds, we can learn more about what's possible, likely, and unlikely in our Universe. Dive into this fascinating conversation and learn some cutting-edge science along the way!
(This composite image of Pluto and its largest moon, Charon, was based on photographs taken by the New Horizons mission as it flew by the Plutonian planetary system back in 2015. Charon's appearance is vastly different from Pluto's, but both bodies are shown with the correct relative size and albedo. Credit: NASA, APL, SwRI)
When it comes to stars, most of them, for most of their lives, behave in a very similar fashion to the Sun. In their cores, they undergo nuclear fusion, which provides energy and creates radiation, and that outward radiation pressure holds the star up, internally, against gravitational collapse. For most stars, this balance between the pressure from outward radiation and the inward force from gravitation is nearly perfect all throughout the star, leading to an equilibrium state.
But some stars aren't in this kind of equilibrium at all. Instead, some internal process actually drives the star in a fashion that causes it to pulsate: overshooting equilibrium in both directions, as it alternatingly expands and cools, and then contracts and heat up in a cyclical fashion. These species of intrinsic variable stars, including Cepheids and RR Lyrae stars, are not only of profound importance when it comes to understanding stellar evolution, but for unlocking the secrets of the distant Universe.
How do we understand these stars today, where are the frontiers, and what do we hope to learn about them in the coming years and decades? Especially as we transition into the era of "big data" in astronomy, where we aren't observing individual stars in detail but rather thousands upon thousands of similar stars all at once, the answers to these questions are rapidly changing. I'm so pleased to share the first episode of 2025 with you, featuring our guest, Ph.D. candidate Catherine Slaughter, who takes us through all this and more. It's a fascinating look into stellar physics, with possible implications for our own Sun's fate, that you won't want to miss!
(The featured image shows the star RR Lyrae, as imaged by the digitized sky survey back at the turn of the century, using data from the Palomar and UK Schmidt telescopes. Credit: Digitized Sky Survey - STScI/NASA)
When we look out at our home galaxy, the Milky Way, we have to recognize that even though it's been growing and evolving for 13.8 billion years, we're only observing it as it is right now: a snapshot in time determined by the light that's arriving in our instruments right now. However, just like we're living "right now" in human history but can, through the science of archaeology, learn about historical events that happened many thousands of years ago (before recorded history) or even earlier, we can learn about the Milky Way's history through the astronomical equivalent: galactic archaeology.
How do galactic archaeologists do it? They look at as much data as possible, across many wavelengths of light, including at many rare and obscure species of stars, in as many locations as possible and to the greatest precisions possible all at once. By combining these different lines of evidence, we can arrive at a coherent and compelling picture for how our little corner of the Universe grew up, including by reconstructing the merger history of the Milky Way.
Surprisingly, it isn't only the "big data" missions that are contributing to this understanding, but even smaller, less heralded (and more accessible) telescopes, with the right equipment and sets of observations, can make a huge impact. Join us for this episode, where astrophysicist and observatory director Elaina Hyde joins us, helping us better appreciate the wonders of our own cosmic past!
(This illustration of our Milky Way shows an ancient galactic stream wrapped around our galaxy's plane at nearly a 90 degree angle: evidence for a recent and even ongoing merger in our galaxy's history. Credit: NASA/JPL-Caltech/R. Hurt (SSC/Caltech))
In this Universe, there are a few objects that are just larger, and a few events that are just more powerful, than others. As far as size goes, the cosmic web creates some of the largest features ever discovered, with the largest galaxy filaments and the largest regions devoid of galaxies spanning as much as ~2 billion light-years. No robust, verified structure has ever been found that's larger. Meanwhile, as far as energy and power go, collisions of galaxy clusters are the most energetic events, outstripped only by the Big Bang itself.
However, nearly rivaling galaxy cluster collisions are the strongest black hole jets ever seen, capable of emitting trillions of times the energy of a Sun-like star, but also capable of sustaining those energies over timescales of a billion years or more. Astronomers have just set a new record for the longest black hole jet with the discovery of Porphyrion, which spans a whopping 24 million light-years across! How did this jet and others like it come to be, and what effects do they have on the larger Universe, and how do they get generated from such physically small objects (i.e., black holes) to begin with?
That's the subject of the latest edition of the Starts With A Bang podcast, featuring Dr. Martijn Oei: the discoverer of Porphyrion himself! We get deep into the physics and astrophysics of black holes and their jets, which have profound implications for how structures get carved and magnetized onto the scales of the cosmic web itself. Buckle up and tune in; it's a wild ride ahead!
(This illustration shows how black hole jets can be as large as the scale of the cosmic web itself, with Porphyrion, as illustrated here, setting a new cosmic record with its bipolar jets spanning 23-24 million light-years across. Credit: Erik Wernquist/Dylan Nelson (IllustrisTNG collaboration)/Martijn Oei; Design: Samuel Hermans)
It's hard to imagine, but it was only five years ago, in 2019, that humanity feasted our collective eyes on the first direct image of a black hole's event horizon. Thanks to the technique of very long baseline interferometry and the power of arrays of radio telescopes stitched together from all across the Earth, we were able to resolve the event horizon of the black hole M87*, despite the fact that it's an impressive 55 million light-years away.
That was with radio interferometry, but historically, most telescopes have used optical light, not radio light. Does that mean that optical interferometry is possible? Not only is the answer a resounding "yes," but we've been performing it for decades. In fact, the most ambitious optical interferometry project of all-time is already under construction in New Mexico: the Magdalena Ridge Observatory Interferometer (MROI). With an array that will feature a total of ten separate telescopes all linked together, and with a maximum tunable distance of 340 meters between them, it's poised to achieve higher-resolution imagery of a suite of astronomical objects than has ever been obtained before, from the ground or from in space.
There's so much mind-blowing science to learn that we had to bring two guests onto our podcast this month to explain it all: Dr. Michelle Creech-Eakman of New Mexico Tech and Dr. Chris Haniff of Cavendish Laboratory at Cambridge University. Be prepared for a fascinating look at the science of optical interferometry, what we'll be able to discover once MROI is complete, and an incredible tour of the instrumentation science that powers it. It's a fascinating episode you won't want to miss!
(The first two telescopes (of ten) that will eventually be part of the Magdalena Ridge Observatory Interferometer when its full array is complete. Credit: James Luis/MROI)
When you think of an active galaxy, what picture comes to mind? Do you think about a monstrous supermassive black hole feasting on tremendous stores of gas and other forms of matter? Do you picture an enormous disk of accreted matter, being accelerated, heated, and eventually shot out along two jets, each perpendicular to the disk itself? This common picture of active galaxies describes many of the most prominent ones, but isn't universal to them all.
Some active galaxies aren't giant ellipticals, but just average-looking spiral galaxies. Some galaxies aren't in the process of a major merger, but seem to be powered by their own internal gas. And some of these black holes aren't ridiculously massive, with billions of solar masses inherent to them, but are rather much more modest. Some of these active galaxies actually show practically no signs of activity in visible light, but must be viewed in other wavelengths, such as with radio telescopes, to reveal their activity.
Above, you can see galaxy NGC 3227, which may appear to be just a normal spiral galaxy. However, not only is it active, but it's actively in the process of launching a "cone" of energetic material from very close to the black hole itself. Here to help us untangle its mysteries and take us on a deep dive into the physics of these objects, I'm so pleased to welcome Julia Falcone to the podcast. Julia is a PhD candidate at Georgia State University, and her very first published first-author paper is about this exact system shown here. Come join us as we explore these fascinating objects and open a window onto the Universe we're still discovering!
(This image shows galaxy NGC 3227, at left, with its neighbor NGC 3226, as viewed in optical light by the Hubble Space Telescope. Despite copious features common to spiral galaxies, including rich dust lanes, a bright central bulge, and new stars forming along its spiral arms, this galaxy is actually active, with bright features emanating from the central supermassive black hole in non-optical wavelengths of light. Credit: NASA, ESA, and H. Ford (Johns Hopkins University); Image Processing: G. Kober (NASA Goddard/Catholic University of America))
Right now, the Large Hadron Collider (LHC) is the most powerful particle accelerator/collider ever built. Accelerating protons up to 299,792,455 m/s, just 3 m/s shy of the speed of light, they smash together at energies of 14 TeV, creating all sorts of new particles (and antiparticles) from raw energy, leveraging Einstein's famous E = mc² in an innovative way. By building detectors around the collision points, we can uncover all sorts of properties about any known particles and potentially discover new particles as well, as the LHC did for the Higgs boson back in the early 2010s.
But the LHC has a limited lifetime, and by the 2030s, will complete its data-taking runs. If we want to go beyond the LHC, we need to start planning for a new particle collider now, and there are four great options that can take us beyond the current frontier: a linear lepton collider, a circular lepton collider, a circular hadron collider, and a potentially new innovation of a circular muon collider. In this episode of the Starts With A Bang podcast, Dr. Cari Cesarotti joins us to discuss all of these options and much more, as we look ahead to the future of particle physics.
The serious question isn't whether we should build one (we definitely should), but which approach will be most fruitful in pushing our suite of knowledge beyond the known frontiers. There's an entire Universe to explore at the subatomic level, and those of us curious about the Universe want to know what's out there better than ever before!
(This image shows the expected signature of a Higgs boson decaying to bottom-quark jets around the collision point inside a muon collider. The yellow lines represent the decaying background of muons, while the red lines represent the b-quark jets. Credit: D Lucchesi et al.)
On the largest of cosmic scales, the best description we have of our Universe is known as the ΛCDM model with an inflationary hot Big Bang: our consensus cosmology. It tells us that we have a Universe consistent with being made of about 5% normal matter, a little bit of radiation in the form of photons, around 0.1% neutrinos, and the rest made of the mysterious dark matter (~27%) and dark energy (~68%). Governed by General Relativity, this explains what we see on Solar System scales, where dark matter and dark energy are negligible, and on cosmic scales, where dark matter and dark energy are important.
But on in-between scales, we aren't quite sure that this same "consensus cosmology" leads to a very successful description. It's long been known that, on galactic scales, rotating galaxies appear to obey a different force law: MOND, for MOdified Newtonian Dynamics. In MOND, the traditional Newtonian acceleration is replaced, at very low accelerations, by a combination of the Newtonian acceleration with a fundamental new parameter, which prevents accelerations from dropping too far below a certain value: around ~10^-10 meters-per-second-squared. If this deviation is real, it should show up someplace else: in pairs of stars separated by large distances, a class of systems known as wide binaries.
Although this area of physics was widely ignored for decades, new observations with the ESA's Gaia mission have recently brought it back into the forefront, where different teams are claiming different results based on how they use and interpret the data. In this rare edition of the Starts With A Bang podcast, I sit down with astrophysicist Xavier Hernandez of UNAM in Mexico, who's one of the main players in this story and a strong advocate of MOND as an alternative to dark matter. The conversation takes many interesting turns and as a result, we've got a great episode that's nearly two hours long. (Although there is some confusion over the maximum distance that Xavier's sample goes out to in the podcast: the correct answer is not mentioned, but turns out to be ~12,000 AU, not the 6000 or 16,000 mentioned in the podcast.) Take a listen, learn some new astrophysics, but most importantly, stay open to new challenges to the conventional paradigm. If there's a crack in our consensus cosmology, this area of astrophysics might someday be the critical blow that shatters it apart!
(This photo shows the bright, naked-eye star, Albireo. To the naked eye, it appears as just a single point of light. However, a binocular or telescope view shows that it's actually two very different colored stars separated by a substantial fraction of a light year: a wide binary system. Even thousands of years after its identification, we still don't know if this is a bound system, or two stars that happen to be passing one another in close proximity. Credit: Jared Smith/Flickr)
One of the most swiftly forgotten revolutions in all of science is our understanding of the Solar System out beyond Neptune. Although Pluto was discovered nearly a full century ago, it wasn't until the early 1990s that we even discovered the next object beyond Neptune that wasn't also part of the Plutonian system. And yet, in the 30 short years that have passed since then, we've learned so much more about the structure of the Kuiper belt and beyond, but we also face tremendous challenges in the quest to learn more thanks to an unwelcome intruder: the rise of satellite megaconstellations.
Although the original team of Mike Brown and Konstantin Batygin continue to advocate for a novel, massive, undiscovered world located at hundreds of times the Earth-Sun distance, they're largely alone, as other scientists have weighed in and see no evidence for this hypothetical world. Nevertheless, more science must be conducted to know for sure, and in the meantime, the rise of satellite megaconstellations such as Starlink now poses an existential threat to all sorts of endeavors, including planetary astronomy.
Here to guide us through the current status of the hunt for Planet Nine, as well as the new obstacles that astronomers are contending with, I'm so pleased to welcome Prof. Sam Lawler to the show. Sam is a professor at the University of Regina in Saskatchewan, Canada, and is also known for her advocacy work in favor of dark and quiet skies for all of humanity to enjoy and benefit from. It's a fascinating discussion that took me to some unexpected places, and I think you'll enjoy it a whole lot!
(This image shows an illustration of the hypothetical Planet Nine: a planet theorized to be more massive than Earth but hundreds of times farther away from the Sun than our own world. Credit: Tobias Roetsch/Future Publishing)
Every January, I head to the American Astronomical Society's big annual meeting with an ulterior motive in mind. Beyond merely uncovering new scientific findings, gathering information for potential stories, and connecting with friends and colleagues, I also look to meet emerging junior researchers who are swiftly becoming not only experts, but leaders, in their particular sub-field of astronomy.
One of the most popular research topics in astrophysics today is the connection between the dark Universe, including the only indirectly-observed dark matter and dark energy, and the observable components that astronomers routinely see: stars, galaxies, gas, plasma, and other forms of light-emitting and light-absorbing matter. The dark Universe, to date, is best revealed by looking at the luminous, electromagnetic signals that are imprinted onto the visible components of our cosmos.
To better understand what scientists are investigating, I'm so pleased to welcome KeShawn Ivory to the podcast. KeShawn is a PhD candidate at Vanderbilt University and researches the connection between dark matter, the non-luminous, gravitationally interacting "stuff" that holds the Universe together (as best as it can), and the luminous, observable galaxies that populate the visible Universe in numbers that rise into the trillions. It's a fascinating topic and a great addition to your May listening, right here on Starts With A Bang!
(The SIBELIUS project, which simulates galaxies and structures beyond the local Universe, is part of the Virgo Consortium that attempts to use cosmological simulations to reproduce features of galaxies, groups, and clusters that are seen all across the Universe. By using a mix of theory, observations, and simulations, astrophysicists can better understand the nature of dark matter in our cosmos. Credit: Virgo Consortium/SIBELIUS project)
Have you ever wondered what the full story with the galactic center is? Sure, we have stars, gas, and an all-important supermassive black hole, but for hundreds of light-years around the center, there's a remarkable story going on that's traced out in a variety of elements at a whole slew of different temperatures. Imprinted in that material is a remarkable set of features that reveals the magnetic fields generated in our galaxy's core, with some of them spanning much greater distances than have ever been seen elsewhere.
It's a testament to the power of multiwavelength astronomy, and in particular to the long wavelengths like the far-infrared, the microwave, and the radio portions of the spectrum that shows us these features of the Universe that simply can't be revealed in any other way. To help bring this story to all of you, I'm so pleased to welcome Dr. Natalie Butterfield, a scientist at the National Radio Astronomy Observatory (NRAO), to join us on this episode of the Starts With A Bang podcast.
Natalie is the discoverer of a giant magnetized ring some 30 light-years in diameter located in the galactic center, and is one of the leaders of the FIREPLACE survey: the Far-Infrared Polarimetric Large-Area CMZ Exploration survey that used the (sadly, now-defunct) SOFIA telescope to image the galactic center as never before. Strap in and have a listen, because you just might never think about the core of the Milky Way in the same way again!
(This image shows the magnetized galactic center, with various features highlighted, as imaged by the SOFIA/HAWC+ FIREPLACE survey team. The giant bubble at the left of the image is some 30 light-years wide, several times larger than any other supernova-blown bubble ever discovered. Credit: D. Paré et al., arXiv:2401.05317v2, 2024)
All throughout the Universe, galaxies exist in a great variety of shapes, ages, and states. Today's galaxies come in spirals, ellipticals, irregulars, and rings, all ranging in size from behemoths hundreds or even thousands of times larger than the Milky Way to dwarf galaxies with fewer than 0.1% of the stars present here in our cosmic home. But at the centers of practically all galaxies, particularly the large ones, lie supermassive black holes.
When matter falls in towards these black holes, it doesn't just get swallowed, but accelerates and heats up, leading to phenomena like accretion disks, jets, and emitted radiation all across the electromagnetic spectrum. When these conditions exist, we know we have what's called an active galaxy, and it isn't just the rest of the galaxy that's impacted by that central activity, but far larger structures in the Universe beyond.
Here to help us explore these objects and their impact this month is Skylar Grayson, a PhD candidate at the School of Earth and Space Exploration at Arizona State University. Skylar works at the intersection of theory and computational astrophysics, and helps simulate the Universe while focusing on the inclusion and modeling of this type of galactic activity, and is one of the people helping uncover just how profound of a role these galaxies play in shaping the Universe around them. Buckle up for another exciting 90 minute episode; you won't want to miss it!
The powerful radio galaxy Hercules A, shown above, is a stunning example of how central activity from the galaxy's active black hole influences not only the host galaxy, but a large region of space extending far outside the galaxy itself, as visible from the extent of the radio lobes highlighted visually. (Credit: NASA, ESA, S. Baum and C. O'Dea (RIT), R. Perley and W. Cotton (NRAO/AUI/NSF), and the Hubble Heritage Team (STScI/AURA))
Up until the early 1990s, we didn't know what sorts of planets lived around stars other than our Sun. Were they like our own Solar System, with inner, rocky planets close to our star and large, giant worlds farther away? It turned out that exoplanetary systems come in a great variety of configurations: with planets of all sizes, masses, and distances from their parent stars. But some configurations are more common than others.
There are lots of hot Earth-sized planets and lots of hot Jupiter-sized planets, but precious few "hot Neptune" worlds out there. Furthermore, there appear to be lots of Earth-sized and super-Earth-sized worlds at greater distances, as well as many Neptune-sized and mini-Neptune-sized worlds. However, there's a gap there, too: between the large super-Earths and the small mini-Neptunes. Where are these missing exoplanets? Or, rather, why are these classes of exoplanets so uncommon?
That's what we're exploring on this episode of the Starts With a Bang podcast, featuring Ph.D. candidate Dakotah Tyler as our guest this month. By looking at how a hot (but low-mass) Jupiter-sized planet is being photoevaporated by its parent star, we can learn so much about not only the classes of objects we see out there, but even the ones we don't!
(Around the star WASP-69, a "hot Jupiter" exoplanet has its outer layers of atmosphere photoevaporated away, creating a comet-like tail whose extent and mass were recently measured for the first time. Credit: W. M. Keck Observatory/Adam Makarenko)
Happy new year, everyone, and with a new year comes a spectacular new podcast! We normally cover an intricate and underappreciated aspect of astrophysics on the podcast, but I had the opportunity to bring on a true expert in the field of quantum computing and just couldn't pass it up.
You've likely heard a lot of noise about quantum computers and the benefits that they're poised to bring, with buzzwords like "P=NP," "quantum supremacy," and "quantum advantage" tossed around, but a lot of what you're likely to hear is hype, not actual science. Good thing I was able to get Dr. Riccardo Manenti as a guest for our podcast!
Riccardo is the author of a state-of-the-art textbook on quantum computers, has his PhD from Oxford in Quantum Computing, and has been working for Quantum Computing startup Rigetti for several years now. Join us as he helps demystify some of the recent progress and problems right here on the cutting edge of this promising new arena of physics, right here on the Starts With A Bang podcast!
(This illustration show's Rigetti's widely-available quantum computer, Novera, with 9 superconducting physical cubits within it. The great hope is that by scaling up to greater numbers of physical qubits, quantum advantage will be an achievable milestone in the relatively near future. Credit: Rigetti/Novera)
It's hard to believe, but it was only back just a year and a half ago, in mid-2022, that we had yet to encounter the very first science images released by JWST. In the time that's passed since, we've gotten a revolutionary glimpse of our Universe, replete with tremendous new discoveries: the farthest black hole, the most distant galaxy, the farthest red supergiant star, and many other cosmic record-breakers.
What is it like to be on the cutting edge of these discoveries, and what are some of the most profound ways that our prior understanding of the Universe has been challenged by these observations? I'm so pleased to welcome Dr. Jeyhan Kartaltepe to the program, who's not onlya member of the CEERS (Cosmic Evolution Early Release Science) collaboration, but who has spearheaded a number of novel discoveries that have been made with JWST.
In the quest to understand not only what our Universe is and how we fit into that cosmic story, but also the story of how the Universe evolved and grew up to be the way it is today, these are some of the most important questions, concepts, and ideas to consider. It's our 100th episode, and I promise: it's one you won't want to miss!
(This image shows a portion of the CEERS survey's area, viewed with JWST and with NIRCam imagery. Within this field of view lies a galaxy with an active supermassive black hole: CEERS 1019, which weighs in at 9 million solar masses at a time from when the Universe was less than 600 million years old. It was the earliest black hole ever discovered, until that record was broken yet again in November of 2023. Credit: NASA, ESA, CSA, Steve Finkelstein (UT Austin), Micaela Bagley (UT Austin), Rebecca Larson (UT Austin))
You might not think about it very often, but when it comes to the question of "how old is a star that we're observing," there are some very simple approximations that we make: measure its mass, radius, temperature, and luminosity (and maybe metallicity, too, for an extra layer of accuracy), and we'll tell you the age of this star, including how far along it is and how long we have to go until it meets its demise.
This also operates under a simple but not-always-accurate assumption: that all stars of a given mass and composition have the same age-radius and radius-temperature-luminosity relationships. That simply isn't true! Stars vary, both over time as they evolve and also from star-to-star dependent on their rotation and magnetism. It's a funny situation, because just a few years ago, people had declared stellar evolution as a basically "solved" field, and now it turns out that we might have to rethink how we've been thinking about the most common classes of stars of all!
To help us explore this topic, I'm so pleased to welcome Dr. Lyra Cao (pronounced "Tsao" and not "Cow" in case you were interested) to the program, where she helps walk us through what we're only now learning about stars: particularly young stars, low-mass stars, and rapidly rotating stars. If you know nothing about stellar evolution, this will be a treat for you, as you won't have to un-learn a massive amount of information to make sense of the Universe!
(This image shows a temperature profile of star HD 12545, which unlike our Sun, doesn't just have a small number of tiny sunspots on it, but is dominated by a massive, star-spanning starspot that covers approximately 25% of its surface. Many stars, including low-mass, young, and rapidly rotating stars, have enormous sunspots that can play a major role in the habitability of their systems. Credit: K.Strassmeier, Vienna, NOIRLab/NSF/AURA)
Out there in the Universe, there's a whole lot more than simply what we find in our own Solar System. Here at home, the largest, most massive object is the Sun: a bright, hot, luminous star, while the second most massive object is Jupiter: a mere gas giant planet, exhibiting a small amount of self-compression due to the force of gravity.
But elsewhere in the Milky Way and beyond, numerous classes of objects exist in that murky "in-between" space. There are stars less luminous and lower in mass: the K-type stars as well as the most numerous star of all: the red dwarf. At even lower masses, there are brown dwarf stars, possessing various temperatures ranging from a little over ~1000 K all the way down to just ~250 K at the ultra-cool end.
These "in-between" objects, not massive enough to be a star but too massive to be a planet, have their own atmospheres, weather, and a variety of other properties. The thing that limits our knowledge of them, at present, is merely our own instruments. That's why, on this edition of the Starts With A Bang podcast, I'm so pleased to welcome Dr. Brittany Miles, an expert on ultra-cool brown dwarfs and a specialist in instrumentation technology. If you were ever curious about these "in between" objects, you won't want to miss this journey to the frontiers of modern astronomical science!
(This graphic compares a Sun-like star with a red dwarf, a typical brown dwarf, an ultra-cool brown dwarf, and a planet like Jupiter. While brown dwarfs are neither star nor planet, they're fascinating objects in their own right, and very much part of the cosmic story uniting us all. Credit: MPIA/V. Joergens)
When we look at our nearby Universe, it's easy to recognize our own galaxy and the other large, massive ones that are nearby: Andromeda, the major galaxies in nearby groups like Bode's Galaxy, the group of galaxies in Leo, and the huge galaxies at the cores of the Virgo and Coma Clusters, among others. But these are not most of the galaxies in the Universe at all; the overwhelming majority of galaxies are small, low-mass dwarf galaxies, and if we want to understand how we formed and where we came from, it's these objects that we need to be studying more intensely.
So what is it that we already know about them? What has recent research revealed about these tiny galaxies in the nearby Universe, both inside and beyond our Local Group, and what else can we look forward to learning in the relatively near future? Join me for a fascinating discussion with Prof. Mia de los Reyes of Amherst College, as we dive into the science of the tiniest galaxies of all, and what they can teach us about our cosmic history as a whole!
(This image shows a map of stars in the outer regions of the Milky Way, from the northern celestial hemisphere, with several galactic streams visible. The color-coding indicates the distance to the stars, and the brightness indicates the density of stars in that patch of sky. In the white circles are faint companions of the Milky Way discovered by the SDSS: only two are globular clusters, the rest are all dwarf galaxies. Credit: V. Belokurov and the Sloan Digital Sky Survey)
We all knew, if Einstein's General Theory of Relativity were in fact the correct theory of gravity, that it would only be a matter of time before we detected one of its unmistakable predictions: that all throughout spacetime, a symphony (or cacophony) of gravitational waves would be rippling, creating a cosmic "hum" as all of the moving, accelerating masses generated gravitational waves. The intricate monitoring of the Universe's greatest natural clocks, millisecond pulsars, would be one potential way to reveal this cosmic gravitational wave background.
But not many expected that here in 2023, we'd be announcing the first robust evidence for it already, and that future studies will reveal precisely what generates it and where it comes from. Yet here we are, with pulsar timing taking center stage as the second unique method to directly detect gravitational waves in our Universe!
For this edition of the Starts With A Bang podcast, I'm so pleased to welcome Dr. Thankful Cromartie to the show, where she guides us through the gravitational wave background, the science of pulsar timing arrays, and the underlying astrophysics of the objects that we monitor with them: millisecond pulsars. It's a fascinating story and one that's more accessible than ever with this latest podcast, and I hope you learn as much as I did listening to it!
(The illustration shown here maps out how merging black holes from all across the Universe generate ripples in spacetime, and as those ripples pass across the lines-of-sight from a millisecond pulsar to us, those signals create timing variations across this natural array. For the first time, in 2023, we've detected strong evidence indicating the presence of this cosmic gravitational wave background. Credit: Daniëlle Futselaar (artsource.nl) / Max Planck Institute for Radio Astronomy)
Sometimes, it's hard to believe we've come as far as we have, scientifically, in such a short period of time. We only began accumulating the first very strong evidence for supermassive black holes during the 1990s, and yet here we are, less than 30 years later, studying them, their effects, and their environments all across the Universe: from the present day to less than 1 billion years after the Big Bang.
We now believe that nearly every galaxy out there in the Universe not only produces black holes from the corpses of the most massive stars within them, but also supermassive ones that resides at the centers of these cosmic objects. Every once in a while, these supermassive black holes accrete matter and devour some of it, becoming active in a spectacular display. Just as we're learning all about how the Universe grows up in terms of stars, atoms, and gas, we're starting to learn how these supermassive black holes evolve and grow up, too.
Here to guide us through the latest and greatest scientific discoveries, I'm so pleased to welcome Dr. Allison Kirkpatrick onto our show. Allison is a professor at the University of Kansas and specializes in supermassive black holes, from X-ray to radio observations and well beyond. Join us on this exciting journey to the heart of one of our greatest cosmic mysteries, and see what it's like at the frontiers of science here on Starts With A Bang!
(This image is the first mid-infrared image of Stephan's Quintet ever taken by the James Webb Space Telescope. The galaxy at the topmost-right of the image displays a brilliant spikey pattern: evidence of a supermassive black hole that had never been revealed prior. Credit: NASA, ESA, CSA, STScI)
We have a pretty good idea of both what's in our Universe and how it grew up. But it's only because we have several different, completely independent lines of evidence that point to the same consensus picture that we actually believe that our Universe is 13.8 billion years old and composed of a mix of normal matter and radiation, but is dominated by dark matter and dark energy on the largest of cosmic scales.
In particular, we form large, cosmically bound structures on the scales of galaxies and galaxy clusters, but on larger scales, dark energy and the expanding Universe dominate, working to drive everything apart. The story of how we've come to know this information about the Universe and how we're using both old and new techniques to push the our understanding further is the subject of this edition of our podcast. It features PhD candidate Karolina Garcia, who's kind enough to walk us through a variety of types of research that all serve the same end: to reveal the story of the Universe and how it grew up to be the way it is today. Take a listen; you won't regret it!
(This image shows a series of structure-formation simulations: at low resolution, medium resolution, and superior/high resolution, for both cold dark matter and fuzzy dark matter models. If we can measure the Universe precisely and accurately enough, we can distinguish between these types of models, contingent on whether we simulate it to great enough precision. Credit: M. Sipp et al., MNRAS (submitted), 2023)
One of the most exciting possibilities for life beyond Earth doesn't require us going very far. While Mercury and the Moon have no atmosphere and Venus is an inferno-esque hellscape, Mars offers a tantalizing possibility for a new line of life, independent of Earth, here in our Solar System. With the same raw ingredients and more than a billion years of a watery, wet past, Mars could have had, or might even still have today, some form of life on its surface.
Part of the reason Mars is so exciting for us is that we've been there: at least, robotically, with a series of orbiters, landers, and even rovers. We've seen and learned so much about the red planet, including some tantalizing hints of what might be biological activity. But there's so much more to learn, and we're reaching the limits of what we can accomplish without having human beings walk on the Martian surface.
On this episode of the Starts With A Bang podcast, we're joined by Mars expert Dr. Tanya Harrison, who's worked on three generations of Mars Rovers and is a strong advocate for a variety of future missions to Mars. Join us for this fascinating conversation where she lays out what we know, what remains uncertain, and what we'll need to do if we want to take those next, critical steps. (And, as a bonus, she corrects one or two of my misconceptions along the way!)
(This image shows the Mars Perseverance rover in one of its "selfie-mode" images, where its own tracks and the Ingenuity rover are both visible in the background. Credit: NASA/JPL-Caltech/ASU/MSSS/Seán Doran)
Back in the 1990s, observations of type Ia supernovae were the key data set that led astronomers to conclude that the Universe's expansion was accelerating, and some new form of energy, now known as dark energy, was permeating the Universe. Over the past ~25 years, those observations have gotten so good that we now have a tension within the expanding Universe, as different methods of measuring the expansion rate yield two different sets of mutually incompatible results.
What's remarkable is that this result is robust even though we're still somewhat uncertain as to exactly how these type Ia supernovae occur. The original scenario, put forth by Chandrasekhar nearly a century ago, still has its adherents, but the evidence appears very strong that approaching and reaching a "mass limit" beyond which atoms are unstable can only explain a small fraction of white dwarf behavior. Instead, a new paradigm dominated by merging white dwarfs may explain nearly all type Ia supernova explosions!
On this episode of the Starts With A Bang podcast, we talk to UC Berkeley astronomer Dr. Ken Shen, a theorist whose expertise lies in type Ia supernovae, and learn how just the last 20 or so years have led to a revolution in how we conceive of these "standard candles" in the Universe, and just what observations might soon lead us to know, for certain, how these cosmic events are truly triggered!
(The titular illustration shows two merging white dwarfs, the preferred theoretical mechanism for the triggering of some, and perhaps most or even nearly all, type Ia supernovae. The double detonation scenario, where a "detonation" event on the surface propagates to the core and causes a detonation that leads to total destruction of the stellar remnant, it one very intriguing theoretical possibility. Credit: D. A. Howell, Nature, 2010)
When stars are born, they can come with a wide variety of masses. But there are only a few ways that stars can die, and only a few types of remnants that can be left behind: white dwarfs, neutron stars, and black holes. Neutrons stars and black holes are most frequently created from core-collapse supernova events: the deaths of massive stars. Somewhere, even though we're not sure exactly where it is, there's a dividing line between "what makes a neutron star?" and "what makes a black hole?" Somewhere out there, there's a heaviest neutron star, and someplace else a lightest black hole.
But the dividing line might not be so clean, after all. It turns out that when neutron stars merge, they can form another neutron star, a black hole, or a third case: an in-between scenario. In this third case, you can temporarily form a hypermassive neutron star: a neutron star that's too massive to be stable, but that collapses in short order to a black hole, but only after persisting as a neutron star for a detectable amount of time.
To help guide us through the science of hypermassive neutron stars, I'm so pleased to welcome Dr. Cecilia Chirenti to the show, a joint scientist at NASA Goddard and the University of Maryland, College Park. There's a whole lot of cutting-edge science right at (and even over) the horizon of what we know today, and you won't want to miss this information-rich episode!
(This image shows the illustration of a massive neutron star, along with the distorted gravitational effects an observer might see if they had the capability of viewing this neutron star at such a close distance. Credit: Daniel Molybdenum/flickr and raphael.concorde/Wikimedia Commons)
One of the great advances of 20th and 21st century science has been, for the first time to show us two things: how the Universe began and what the Universe looks like today. The modern frontier is all about the in-between stages: how did the Universe grow up? How did it go from particles to atoms to the first stars and galaxies to the modern Milky Way, Local Group, and Universe-at-large? It's a question that, the more deeply we answer it, the greater the number of details that emerge, requiring us to make a special effort to pin each one down.
For this episode, I'm so pleased to welcome Dr. Ivanna Escala to the podcast: an expert in how stars and stellar properties within the Local Group can reveal not only its stellar history, but its history of galactic assembly. While the Milky Way has had a few major mergers, its most recent was a whopping ~10 billion years ago. Andromeda, our Local Group's other large galaxy, has a remarkably different story: with a major merger that occurred only 2-4 billion years ago!
Have a listen and enjoy, and thanks to Avenues Online for being our sponsor!
(This image, assembled from very long wavelengths of light of the neighboring Andromeda Galaxy, shows features within Andromeda's galactic disk as well as the gas clouds of neutral hydrogen found in Andromeda's galactic halo. By examining these features, as well as streams and stars in and around Andromeda, we can reconstruct precisely how this galaxy came to be the way it is today. Credit: NRAO/AUI/NSF, WSRT)
For life on Earth, there's no more important source of energy than the Sun; without it, it's doubtful that life would have arisen on Earth, and it certainly wouldn't have evolved to give rise to the wild diversity of biological organisms seen today. But the Sun is more than just a constant source of heat and light; it also emits particles, and there's a darker side to that activity: flares, coronal mass ejections, and the threats this space weather poses to living planets like our own.
It turns out that for technologically advanced civilizations like our own, the threats that arise from the Sun are far greater and more dangerous than at any time prior in Earth's history, and despite the knowledge we have of what the Sun can do to the Earth, we're woefully unprepared for the inevitable. Thankfully, there are not only people studying it, but many of them are also fighting and advocating for solutions and planetary protection, including Sierra Solter, a plasma physicist specializing in solar plasmas, who joins us on this edition of the Starts With A Bang podcast.
Welcome to a glorious 2023, and may we learn the needed lessons for what must be done before we're left with the sad alternative of simply picking up the pieces!
(This illustration shows a massive space weather event, larger than a typical solar flare, known as a surface mass ejection. Although SMEs have the capacity to entirely destroy a planet, they're thankfully limited to occurring on red supergiants, a class of star that will never include our Sun or anything it will evolve into. Credit: NASA, ESA, Elizabeth Wheatley (STScI))
For a cosmologist like me, "cosmic dust" is a thing that's in the way, confounding our data about the pristine Universe, and it's a thing to be understood so that it can be properly subtracted out. But the old saying, that "one astronomer's noise is another astronomer's data," proves to be more true than ever with cosmic dust, as how it's produced, where it came from, and how it comes together to form planets, molecules, and eventually creatures like us, are some of the most essential elements necessary for us to exist within this Universe.
In visible light, cosmic dust is normally just a starlight blocker, but in other wavelengths of light, its composition, distribution, density, grain size, polarization, and many other kinetic and thermal features can be revealed. Here to guide us through the ins-and-outs of cosmic dust, with a special view towards millimeter, submillimeter, and radio wavelengths, I'm so pleased to welcome PhD candidate Carla Arce-Tord to the show. Enjoy this far-ranging tour of cosmic dust, and perhaps by the end you'll walk away inspired about all there is to know as well as the remarkable people making it happen!
(The image shows the magnetic field lines imprinted by the galaxy on the cosmic dust in the interstellar medium, as revealed by the Planck CMB experiment. These field lines are of microgauss strength and can be coherent over hundreds or even thousands of light-years. Credit: ESA/Planck Collaboration. Acknowledgement: M.-A. Miville-Deschênes)
The supermassive black holes at the centers of galaxies is a tremendously interesting area of research, advancing rapidly over the past few years. While most of these observations focus on either high-energy or radio emissions from them, there's a recent push to see what these objects are doing in other wavelengths of light, as well as how they vary in time.
Once, it was thought that supermassive black holes would become "activated" at a certain point in time, would remain on for hundreds of thousands or even millions of years, and would then turn-off. But our observations have shown us that there are remarkable variations in what types of light and energy these objects emit over time, and with new studies being conducted at the South Pole and other places studying the Universe in millimeter-wavelength light, we're about to get an unprecedented amount of high-quality data.
Here to guide us through what we've learned so far about these active galaxies and where this research might take us in the future is Dr. John Hood, a postdoctoral research associate at the University of Chicago. It's a wild ride here at the frontiers of science, and I hope you enjoy every minute of it!
(In this artistic rendering, a blazar is accelerating protons that produce pions, which produce neutrinos and gamma rays when they decay. Lower-energy photons are also produced, allowing blazars, a form of Active Galactic Nucleus (AGN) to be seen all across the electromagnetic spectrum. In recent years, we’ve advanced to the point where we’re detecting neutrinos from billions of light-years away, beginning with blazar TXS 0506+056. Credit: IceCube collaboration/NASA)
All throughout the Universe, we see stars and galaxies everywhere we look. But as we look to greater and greater distances, we're only seeing the light that's the easiest to see: the ones from the brightest, most visible objects. But the most numerous objects of all are exactly the opposite: less luminous, smaller, and lower in mass. How can we hope to find and catalogue them all if they're the hardest ones to find?
The answer lies in measuring the closest stars to us. If we can measure the stars that persist in our own backyard, cataloguing them and taking as complete a census as possible, we can then combine what else we know about stars and starlight and the environments in which new stars form to reconstruct precisely what we believe is out there: not just here-and-now, but elsewhere and all throughout cosmic time.
Here to bring us up to speed on how this attempt to catalogue and categorize the stars in the Universe, I'm so pleased to welcome PhD candidate at Georgia State University Eliot Vrijmoet to the show, who takes us on a fascinating journey to the edge of our knowledge, and from there we'll peer over the horizon to what just might come next. Enjoy the latest episode of the Starts With A Bang podcast!
Star density maps of the Gaia Catalogue of Nearby Stars. The Sun is located at the centre of both maps. The regions with higher density of stars are shown; these correspond with known star clusters (Hyades and Coma Berenices) and moving groups. Each dotted line represents a distance of 20 parsecs: about 65 light-years. (Credit: ESA/Gaia/DPAC - CC BY-SA 3.0 IGO)
All throughout the Universe, we see stars and galaxies everywhere we look. But as we look to greater and greater distances, we're only seeing the light that's the easiest to see: the ones from the brightest, most visible objects. But the most numerous objects of all are exactly the opposite: less luminous, smaller, and lower in mass. How can we hope to find and catalogue them all if they're the hardest ones to find?
The answer lies in measuring the closest stars to us. If we can measure the stars that persist in our own backyard, cataloguing them and taking as complete a census as possible, we can then combine what else we know about stars and starlight and the environments in which new stars form to reconstruct precisely what we believe is out there: not just here-and-now, but elsewhere and all throughout cosmic time.
Here to bring us up to speed on how this attempt to catalogue and categorize the stars in the Universe, I'm so pleased to welcome PhD candidate at Georgia State University Eliot Vrijmoet to the show, who takes us on a fascinating journey to the edge of our knowledge, and from there we'll peer over the horizon to what just might come next. Enjoy the latest episode of the Starts With A Bang podcast!
Star density maps of the Gaia Catalogue of Nearby Stars. The Sun is located at the centre of both maps. The regions with higher density of stars are shown; these correspond with known star clusters (Hyades and Coma Berenices) and moving groups. Each dotted line represents a distance of 20 parsecs: about 65 light-years. (Credit: ESA/Gaia/DPAC - CC BY-SA 3.0 IGO)
Although it seems like a long time ago, it was as recent as the early 1990s that we had no idea whether planets in the Universe were universal, common, uncommon, or even exceedingly rare. While certain data sets once seemed to indicate that practically every star in the Universe had planets around it, we now know that isn't true at all. Many stars, perhaps even most of them, have planets, but plenty of others don't. In addition, the number and types of planets that exist, including planets without parent stars at all, are still under investigation, and the field of planet formation has become extremely active.
With new data coming in from infrared and radio observatories, including JWST and ALMA, we're learning so much about the planets that form in the Universe, including what conditions they form under and what the various important, dominant considerations are. Here as our latest guest on the Starts With A Bang podcast, to help us disentangle what's known from what remains a curiosity, is Dr. Kamber Schwarz, postdoctoral research associate at MPIA Heidelberg.
There's still so much to learn, but wow, how much we know today compared to the early 1990s is astounding. Enjoy this look at the frontiers of what we know about how planets are made, and I hope it leaves you wondering about what else we'll learn in the very near future!
[This two-toned image shows an illustration of the protoplanetary disk around the young star FU Orionis, which was imaged multiple times by the Hubble Space Telescope but years apart. The disk has changed, indicating that it's entering a more advanced stage of evolution, as planets form and the material available for forming and growing them evaporates, sublimates, and is otherwise blown away. (Credit: NASA/JPL-Caltech)]
From the earliest stages of the hot Big Bang up through and including the present day, one cosmic picture is sufficient to describe practically everything we observe: the Lambda-Cold Dark Matter (ΛCDM) cosmological model. With a mix of dark matter, dark energy, normal matter, photons, and neutrinos, we can not only model, but can simulate the Universe from the earliest times and the smallest scales up through to the present and the full scale of the observable Universe.
In most cases, theory and observation match, and spectacularly so. But there are a few current points of tension: cosmological mysteries, that range from the expansion rate of the Universe to small-scale structure formation to the link between the pre-Big Bang Universe and our current dark-energy-caused accelerated expansion.
Where are we, how far have we come, and how far do we still have to go? I'm so pleased to welcome Dr. Santiago Casas, who specializes in many of the same sub-areas of cosmological physics I specialized in about a decade earlier, to our podcast. In this nearly 90-minute long episode, we cover a slew of fascinating topics in more depth and detail than normal, and I hope you enjoy the extra-deep dive into some of the weediest areas of modern cosmology!
This image shows a 15 million light-year long structure that arises from a detailed simulation of the cosmic web and how galaxies, galaxy clusters, and cosmic filaments form on the largest scales of all. Although this theoretical simulation, like many aspects of our standard cosmological models, largely agrees with our observations, there are points of tension that must not, despite the successes, be ignored. (Credit: Jeremy Blaizot, SPHINX project, https://sphinx.univ-lyon1.fr/)
Since the advanced LIGO detectors first began operating in 2015, we've not only directly detected our first gravitational wave signals from merging objects in the Universe, we've observed close to 100 such systems that have emitted detectable gravitational wave signals. All of them to date, however, are the result of short-period, low-mass stellar remnants that have inspiraled and merged into one another. The most massive black holes, at least in gravitational waves, remain elusive.
If all goes well, however, that won't be the case for long. At the centers of very massive galaxies, there's often not just one supermassive black holes, but multiples. Ultramassive binary black holes, in fact, send such energetic ripples through spacetime that they ought to distort, in measurable ways, the arriving radio signals from pulsars distributed all throughout the Milky Way. By monitoring these pulsars extensively through a series of timing arrays, we just might be able to extract information about the longest-wavelength gravitational waves that fill the Universe.
Here to walk us through what we're looking for, how we're conducting this science, what we've seen so far, and what the prospects are for gravitational wave direct detection in an entirely new regime is Dr. Caitlin Witt, who I'm so pleased to welcome to the Starts With A Bang podcast. We've got a 100 minute spectacular for this episode, and you won't want to miss a single moment of it!
Image: This illustration show how the Earth, itself embedded withing spacetime, sees the arriving signals from various pulsars delayed and distorted by the background of cosmic gravitational waves that propagate all throughout the Universe. The combined effects of these waves alters the timing of each and every pulsar, and a long-timescale, sufficiently sensitive monitoring of these pulsars can reveal the gravitational signals. (Credit: Tonia Klein/NANOGrav)
It's now been nearly a full six months since the JWST was launched, and we're on the cusp of getting our first science data and images back from some 1.5 million kilometers away. There are all sorts of things we're bound to learn, from discovering the farthest galaxies of all to examining details in faint, small objects to searching for black holes in dusty galaxies and a whole lot more. But what's perhaps most exciting are the things we're going to find that we aren't expecting, simply because we've never looked in this particular fashion before.
I'm so pleased to welcome two guests to the show: Research Professors Dr. Stacey Alberts and Dr. Christina Williams both join me this month, and we have a far-ranging conversation about infrared astronomy and all that we're poised to learn from exploring the Universe in the infrared as never before. If you're already excited about JWST and what we're going to learn from it, wait until you listen to this episode!
(Image: Although Spitzer (launched 2003) was earlier than WISE (launched 2009), it had a larger mirror and a narrower field-of-view. Even the very first JWST image at comparable wavelengths, shown alongside them, can resolve the same features in the same region to an unprecedented precision. This is a preview of the science we'll get. Credit: NASA and WISE/SSC/IRAC/STScI, compiled by Andras Gaspar)
When we look out at the Universe, what we see is typically what we think of: the points of light. Depending on the scales we're looking at, this can come in the form of stars, galaxies, or even clusters of galaxies, but it's almost always information that comes to us in some form of electromagnetic radiation, or light. But sometimes, light can be just as informative for what either isn't there or how it's been affected by the various media that it's passed through!
In the case of our own cosmic backyard, a new study from earlier this year, 2022, revealed something spectacular and entirely unexpected: that the Sun sits at the center of a ~1000 light-year wide structure known as the Local Bubble, itself just about 15 million years old but containing all of the nearest young star clusters to us. In fact, the star Aldebaran, one of the brightest in the sky, helped "blow" this bubble in the interstellar medium!
It's the very first episode of the Starts With A Bang podcast ever to feature multiple guests, and I'm so pleased to welcome Drs. Catherine Zucker, Alyssa Goodman, and João Alves to the podcast, all three of whom helped make this knowledge possible! I hope you enjoy the listen, and it's a 90 minute spectacular you won't regret spending your time on!
Links:
Discovery paper: https://www.nature.com/articles/s41586-021-04286-5
Press release: https://www.cfa.harvard.edu/news/1000-light-year-wide-bubble-surrounding-earth-source-all-nearby-young-stars
Video: https://sites.google.com/cfa.harvard.edu/local-bubble-star-formation
Interactive visualization: https://faun.rc.fas.harvard.edu/czucker/Paper_Figures/Interactive_Figure1.html
(This visualization shows the Sun's location at the center of a structure about 1000 light-years across known as the Local Bubble. Recent episodes of star-formation have led to a series of new star clusters, shown in the illustration, which have formed a bubble and pushed it out. The Sun has only entered this region recently, and just happens to be at the center now, when we're looking. Credit: Leah Hustak/STScI)
Have you ever wondered how it is that we know all we do about galaxies? How they formed, what they're made of, how we can be certain they contain dark matter, and how they grew up in the context of the expanding Universe? In any scientific discipline, we have the things we know and can be quite confident in, the things that we think we've figured out but more data is required to be certain, and the things that remain undecided given the current evidence: things over the horizon of the present frontiers.
Fortunately, we have the ability to scrupulously identify which aspects of galaxy formation and evolution fall into each category, and to walk right up to the edge of our knowledge and peer over that ever-expanding horizon. Joining me for this episode of the Starts With A Bang podcast is scientist Arianna Long, Ph.D. candidate at the University of California at Irvine and soon-to-be Hubble Fellow at the University of Texas at Austin. With the advent of ALMA and the James Webb Space Telescope, in particular, we're poised to seriously push back the frontiers of the unknown, and you can get the insider's view of exactly what we'll be looking for and how. This is one episode you certainly won't want to miss!
Image: This view of a portion of the DREaM simulated galaxy catalog provides a snippet of sky that might correspond, statistically, with what James Webb expects to see. This particular snippet showcases an incredibly rich region of relative nearby galaxies clustered together, which could provide Webb with an unprecedented view of galaxies magnified by strong and weak gravitational lensing. (Credit: Nicole Drakos, Bruno Villasenor, Brant Robertson, Ryan Hausen, Mark Dickinson, Henry Ferguson, Steven Furlanetto, Jenny Greene, Piero Madau, Alice Shapley, Daniel Stark, Risa Wechsler)
Every time we've figured out a different way to look at the Universe, going beyond the capabilities of our own meagre senses, we've opened up an opportunity to learn something new about what's out there. Although optical astronomy and near-infrared astronomy are arguably the most popular ways to view the Universe, with James Webb soon to bring the mid-infrared Universe into view as never before, we shouldn't forget about the value of other, more distant wavelengths of light.
One of the most fascinating sets of data that we can collect is in the far-infrared, where gas heated to just a few tens of Kelvin shines, but where much hotter, even ionized gas can emit very special hyperfine transitions. Mapping out these regions of space helps us understand what's going on beyond mere star-formation or other violent events, and a series of remarkably specific observational techinques are, quite arguably, how we're obtaining the most valuable information of all in this part of the electromagnetic spectrum.
Joining the Starts With A Bang podcast to help guide us through the topic of far-infrared astronomy is Dr. Jessica Sutter, an astronomer at NASA Ames who's part of the USRA and who works with the SOFIA telescope, a one-of-a-kind far-infrared observatory that can do what no ground-based nor space-based observatory can. Have a listen, and I hope you wind up learning as much as I did!
(The featured image shows galaxy NGC 7331 along with other members of its galactic group, including the prominent galaxies NGC 7335, 7336, 7337, and 7340. Credit: Vicent Peris/c.c.-by-2.0)
When you start looking at the Universe, you realize that there are more signals out there than are simply generated by stars. On the one hand, you have astrophysical objects like gas, dust, plasma, as well as stellar corpses and their remnants. But there are also failed stars that didn't quite make it to the nuclear fusion stage that defines our Sun and the other stars like it: brown dwarfs.
Beyond that, there may also be signatures of planets like Earth out there: planets inhabited by an intelligent civilization. It's of paramount importance, when asking the biggest questions, to make sure that we aren't fooling ourselves, but that's where projects like SETI and Breakthrough Listen come in: to help us extract legitimate science where "wishful thinking" has the potential to lead us in precisely the most dangerous direction: the possibility of fooling ourselves.
I'm so pleased to welcome Ph.D. Candidate Macy Huston to the podcast, as we explore the less commonly seen side of the Universe: from exoplanets to brown dwarfs to the search for extraterrestrial intelligence. With the advent of the James Webb Space Telescope, we really are going to see a tremendous change in what we know!
Some stars, as they go through their life cycles, will die of natural causes. They'll burn through their fuel until they can fuse elements no longer, and then will die, becoming a white dwarf below a certain mass threshold, or experiencing a core-collapse supernova that leaves behind a neutron star, a black hole, or perhaps something even more interesting above that mass threshold. But some stars, while just going about their lives, can suffer a wildly different fate: they can be murdered by other objects in the Universe. Stellar destruction can take many forms and can give off many different unique signals, and it's only by examining a wide range of the electromagnetic spectrum, as well as other types of sources, that we can decode what's actually going on across the Universe.
I'm so pleased to welcome Dr. Yvette Cendes to the program, who specializes in radio astronomy and the behavior of exotic objects that change their behavior over time: transient signals. There's so much to explore and I hope you enjoy this fascinating 90 minute discussion right here on the Starts With A Bang podcast!
(Credit: Alak Ray, Nature Astronomy, 2017; ACTA/ALMA/ESO/Hubble/Chandra composite)
When it comes to the black holes that populate the Universe, they range from the very tiny, of only ~3 solar masses or so and with event horizons that span only a few kilometers, all the way up to the incredibly supermassive, many billions of times as massive as our Sun, with event horizons on the scale of the entire Solar System. These black holes are fascinating not only for how they form and exist, but how they impact and shape the entire galaxies that they inhabit. At all different wavelengths, from X-ray to radio, as well as in gravitational waves, we're only starting to uncover the previously elusive science about these cosmic behemoths, and while we're all the richer for it today, it's fascinating to consider what questions we'll be answering decades down the line, too.
Come have a listen to all of these topics and much, much more as we go on a fascinating journey concerning supermassive black holes with Dr. Adi Foord of Stanford, and expose the mysteries of the largest single structures in the entire Universe!
(Image credit: NASA)
You know how it works, right? Point your telescopes at the sky, collect the data, and then send it off to the scientists for analysis and to compare with the predictions of your theories. Only, if that's what you do, you'll miss a crucial first step: you have to handle your data correctly. That means understanding the nuances of your telescope, the sensitivities of your instruments and optics across different filters and wavelengths, and so many other considerations before that data you've collected could ever be responsibly used for any scientific purposes at all.
But this is not a hopeless task; there are entire careers in telescope and instrument support sciences that, in many ways, are the unsung heroes of the entire enterprise of astronomy. In this edition of the Starts With A Bang podcast, I'm so pleased to get to bring Dr. Heather Fleweling onto the show, where she talks about her experience and expertise doing precisely this for observatories such as Pan-STARRS, which she helped build herself, to the Canada-France-Hawaii Telescope (CFHT), where she currently works, specializing in the MegaPrime instrument. Get a behind-the-scenes peek at a corner of astronomy that most people don't even know exists!
In the science of astronomy, it's important to see both the forest and the trees. Galaxy clusters, in many ways, serve as both. They're rich environments with stars, gas, dust, dark matter, black holes and more. The diversity of stars and stellar populations found within them, as well as found within galaxies of different shapes, sizes, and properties within those clusters, are part of a remarkable and coherent cosmic story. But sometimes the cosmic story can help us understand what's going on in these environments, the converse of the way we normally think about it: where we use the environment to learn about the universe.
Come take a fascinating journey into these cosmic behemoths that are the gathering grounds for the greatest collections of large galaxies in the universe, and enjoy a delightful conversation with Gourav Khullar as we go along on this wild ride!
(Image credit: ESA/Hubble and NASA, H. Ebling)
If you want to understand the origin of life in the Universe, you have three basic ways to do it. One is to search for intelligent aliens directly: through a program such as SETI. Another is to search for life in Solar Systems beyond our own: looking for bio-signatures, or perhaps bio-hints, on extraterrestrial worlds many light-years away. But within our own Solar System, there are a plethora of worlds, including the ice-and-liquid-rich bodies we have, that are fascinating candidates for life of non-Earth origin.
There's so much to explore and so many different aspects of what's out there that I went into an incredibly far-ranging conversation with our podcast guest, planetary scientists and NExSS postdoc Dr. Jessica Noviello, that we wound up talking for nearly two full hours, and still couldn't cover everything we wanted to! Still, it was an amazing conversation for me and I hope it is for you, too. Enjoy it!
(Image credit: NASA/JPL/Ted Stryk, of Europa with its uniquely curved stripes, for the Galileo mission.)
Practically every galaxy in the Universe has a supermassive black hole at their core. Ranging from millions to many billions of solar masses, these cosmic behemoths are capable of behaving as engines: accreting and accelerating matter to tremendous speeds and temperatures, where they emit enormous amounts of radiation. Galaxies can remain in this active state for hundreds of millions of years, where they appear to us as active galactic nuclei or quasars, depending on their specific properties.
But why are some galaxies active while others aren't? How long will the active ones we see remain active, and will some of the inactive ones turn on? What about flares? As it turns out, there's a powerful connection between the surrounding galaxy, the processes occurring at the core, and the activity levels of the central black hole. Here to help us put it all together is Dr. Yashashree Jadhav, who takes us on a fascinating and far-ranging discussion about black holes, gas, stars, and much, much more! Enjoy it all on this edition of the Starts With A Bang podcast!
(The image here is a multiwavelength view of the galaxy Centaurus A: the closest active galaxy to the Milky Way. Image credit: X-ray: NASA/CXC/SAO; Optical: Rolf Olsen; Infrared: NASA/JPL-Caltech.)
Like everything in the Universe, stars are born, they live a little while, and then they die. But despite their similarities in terms of where they come from and what they're made of, these objects can have an enormous variety of fates that they experience, and there are some fascinating intermediate and near-final states along the way. Beyond that, the unique stories of the people who made those key discoveries that have brought us to where we are can help us understand exactly how we pieced together the stellar picture of our Universe's history together.
I'm so pleased to welcome Emily Levesque, professor at the University of Washington, author of The Last Stargazers, and enthusiastic lover of the Universe beyond planet Earth to the podcast. This ~80 minute episode was one of my favorites, and showcases Emily's knack for combining her vast knowledge of astronomy with her passion for sharing those stories with the entire world. Have a listen on the latest installment of the Starts With A Bang podcast!
(Image credit: Emily Levesque / Perimeter Institute.)
When we think about the Universe as a whole, the accelerations that objects experience from our perspective are overwhelmingly due to the expansion of the Universe. Nearby, however, it's the local gravitational effects of nearby masses that dominate. Within our own Local Group, we've been able to discover that the Milky Way is not some quiet, massive spiral just going about its own business, but rather that it's being tugged in a variety of ways from the large masses around it, including a nearby galaxy that was only discovered in very recent years: Antlia 2.
This is one of the most exciting detective stories we've gotten to uncover in recent years, as the resolution of this mystery showcases how improved, high-resolution data taken over long periods of time can enable us to witness galactic changes, directly, on the timescale of a single human lifetime. Here to walk us through what we know, how we know it, and what comes next is Prof. Sukanya Chakrabarti of the Rochester Institute of Technology, and I think you'll really enjoy what turned out to be a deep and far-ranging conversation about astronomy right in our own cosmic neighborhood!
(Image credit: V. Belokurov and A. Smith; acknowledgement: Markus and Gail Davies; Robert Gendler)
When you think about how astronomy works, you probably think about observers pointing telescopes at objects, collecting data about their properties, and then analyzing that data to determine what those objects are truly like, and to infer what they can teach or show us about the Universe. But that's a rather old-fashioned way of doing things: one that's contingent on there being enough astronomers to examine all of that data manually. What do we do in this new era of big data in astronomy, where there aren't enough astronomers on Earth to even look at all of the data by hand?
The way we deal with it is fascinating, and involves a mix of statistics, classical analysis and categorization, and novel techniques like machine learning and simulating mock catalogues to "train" an artificial intelligence. Perhaps the most exciting aspect is how thoroughly the best of these applications continuously outperform, in both quality and speed, any of the manual techniques we've used previously. Here to walk us through this exciting and emerging field of machine learning in astronomy is Sankalp Gilda, PhD candidate and astronomer from the University of Florida. We've got a great 90 minutes here for you, so buckle up and enjoy the ride!
(Image credit: VLT Survey Image / ESO; Acknowledgement: Aniello Grado & Luca Limatola)
Swarming through our own galaxy, we've detected quite a few bizarre objects: pulsars. These rapidly spinning neutron stars are only a few kilometers across, yet contain more mass than our entire Sun. They're denser than a uranium atom's nucleus, and some of them possess the strongest magnetic fields in the known Universe. The fastest-spinning one known rotates about its axis 766 times per second, and they can travel at up to ~65% the speed of light. And outside of the ones we've found, we fully expect there might hundreds of millions or even as many as a billion such neutron stars hanging out simply in our Milky Way galaxy.
But they also emit their own light, and a good chunk of that light is polarized, giving us an incredible set of information. In addition, by coordinating the pulse times of many different pulsars, we can not only detect gravitational waves, but can detect the types of waves generated by objects that LIGO and even LISA will never see. I'm so pleased to welcome Haley Wahl, pulsar specialist and PhD candidate, onto the show, and I hope you enjoy what turned out to be a fantastic conversation!
(Image credit: NanoGRAV Collaboration.)
If you look out at the Universe and measure all the matter out there, including stars, gas, dust, plasma, black holes, etc., it simply doesn't add up. You can't explain the gravitational effects you see with the known particles of the Standard Model alone. But even if you add in the one extra ingredient of cold, collisionless dark matter, it only fixes everything to a certain extent. In particular, the small-scale structures of the Universe, on the scales of individual galaxies and below, have a large mismatch between what's observed and what's predicted.
While there are many approaches we can take, and a few different possible explanations, perhaps the most compelling approach is to try and infer what particle properties might dark matter have to bring our observations in line with what our theories and simulations would predict? Here to talk to us about the latest progress on that front is PhD candidate and budding science communicator Sophia Gad-Nasr (a.k.a. @astropartigirl), who joins us for a fascinating ~90 minute discussion on this edition of the Starts With A Bang podcast!
Follow Sophia: -on Twitter, https://twitter.com/Astropartigirl -on her Website, https://astropartigirl.com/ -or on Instagram, https://www.instagram.com/astropartigirl/?hl=en -or TikTok, https://www.tiktok.com/@astropartigirl
(Image credit: Cathrin Machin; NASA, ESA, the Hubble Heritage (STScIAURA)-ESA/Hubble Collaboration, and A. Evans.)
Have you ever wondered what it's like to work as a small (but vital) part of a large collaboration, where hundreds or even thousands of experimental scientists get together to produce an experiment far larger or more complex than any one person could oversee on their own? Have you ever wondered where the line is between physics and astronomy, and whether it even makes sense to have a line at all in the case of astroparticle physics? And have you ever wished that people would be more honest about the recent toxic experiences that they had when they were starting out that are still relevant to young people in those shoes today?
I'm so pleased to have such a remarkable discussion with astrophysicist Niko Sarcevic (pronounced "SHAR-chev-itch" when comes out of my mouth) that's was not only far ranging but incredibly enjoyable for me. I hope you like listening, and if you want to listen to me absolutely botch describing the XENON experiment (which doesn't use the lead shielding I described; that was a different detector: SuperCDMS!), it's well-documented for everyone to hear!
(Image credit: M. van der Wild, using Niko's phone, of the then-under-construction electric field cage that Niko Sarcevic designed and built for the Time Projection Chamber (TPC) for the XENON collaboration.)
You might have thought that if we were going to find life anywhere in the Universe, our best bet would be to look at stars like our Sun, on account of the tremendous success of Earth. It's a good bet, for sure, but did you know that the Sun is brighter and more massive than 95% of stars in the Universe? And that down at the low-mass end of the spectrum, the most common type of objects out there are ultracool dwarfs: low-mass red dwarfs and even brown dwarfs? They have rocky planets around them and could be our first candidate Earth-sized worlds for direct imaging, and are incredible scientific objects of study all on their own.
What do you want to know about them? I'm so pleased to welcome PhD candidate Anna Hughes onto the Starts With A Bang! podcast, and to share her knowledge and wisdom and enthusiasm with all of you. Here's how we start 2021 with a bang, and I hope you enjoy it!
Over the past 2 years, an exciting development has finally arisen: scientists have measured a large number of small, diffuse galaxies exquisitely well, and have finally found their first candidate galaxies that appear to have no dark matter at all. Whereas large cosmic structures typically have dark matter-to-normal matter ratios of 5-to-1, smaller structures typically have higher ratios, as star formation will kick some of the normal matter out but leave the dark matter intact. However, there should be a second type of galaxy: stars without dark matter, as tidal interactions can rip the normal matter out and keep it out. But these structures are easy to destroy, and so shouldn't persist for very long.
How, then, did we find a galaxy that both appears to have no dark matter and also appears to have not formed any new stars in ~7 billion years or more? While the science is still ongoing, I'm so pleased to welcome Dr. Mireia Montes onto the program, whose recent paper may have just solved the mystery. Have a listen and enjoy the show; there's a lot of astronomy in here for you to enjoy!
(Image credit: Montes et al., 2020, ApJ.)
Over the past 30 years, we've gone from zero exoplanets to thousands. With each new generation of telescopes, observatories, and scientists, we build upon our previous finds to make enormous advances that go beyond what any one person could ever produce. The ESA's Gaia mission has surveyed more than a billion stars, identifying the closest ones that would make potentially great targets for NASA's James Webb Space Telescope, if they had potentially habitable planets around them. NASA's TESS is doing the preliminary work of observing these stars, most of which are red dwarf (M-class) stars, to find which ones actually have interesting planets that transit across their parent star's face.
So far, we've found some fascinating candidates, some of which just might be humanity's first discovery of biosignatures beyond our Solar System if we get lucky. This month, we're so fortunate to be joined by astronomer and TESS scientist Emily Gilbert, a Ph.D. candidate who specializes in exoplanets. (And who has the delightful Twitter handle: @EmDwarf.)
Come learn where we are, what we know, and where this rapidly evolving scientific field is headed today!
(Image credit: ENGELMANN-SUISSA ET AL.NASA'S GODDARD SPACE FLIGHT CENTER)
It was only back in the early 2000s that scientists were struggling to identify and weigh the small number of supermassive black holes that we'd been able to identify in the known Universe, but the past 15-20 years have led to a revolution in what we know about them. We've identified tens of thousands of active galaxies, pinned down the masses of some of the closest ones to us through a variety of techniques, and even observed the event horizon of our first black hole directly.
These powerful advances were mainly enabled by superior observatories and instruments, and the spectacular Atacama Large Millimetre/Submillimetre Array (ALMA) of telescopes, which was indispensible to measuring the mass and imaging the event horizon at the core of the largest massive galaxy in our neighborhood: M87.
I'm so pleased to welcome astronomer and Ph.D. Candidate Kyle Kabasares onto the show, where we talk about black holes, mass measurements, ALMA, and the future of black hole-related astronomy! Kyle is also passionate about science outreach, and you can check out his YouTube channel here.
(Image credit: EHT Collaboration; acknowledgement: ESO)
When most of us think of astronomy, we think about two types of scientists: the observers who point their telescopes at the sky and collect data, and the theorists who put together the physical rules of the Universe to both make critical predictions for what those observational results ought to yield and to interpret the data that comes in. But in reality, there are other important types of astronomers that we don't talk about frequently: analysts who focus on dealing with these literally astronomical data sets and the people who work on (and with) the instrumentation itself. This includes telescope and instrument builders, telescope operators and system specialists, and many other vital roles.
Additionally, the science of astronomy isn't just about the science itself, but also questions important for the interplay of science and society. Whose land are these telescopes on? What does responsible stewardship look like? Who has access to these facilities, and who has equal (and unequal) access to the career paths of becoming a scientist?
I'm so pleased to have astronomer Jess Schonhut-Stasik on the show, for a wide-ranging discussion about astronomy, from instruments to injustices and how the big questions about science and society are creating not only incredible dilemmas for astronomy, but an incredible opportunity to get things right. Have a listen today, and check out the fabulous Mauna Kea Scholars program that she's involved with here: https://maunakeascholars.com
(With permission, her email address associated with inquiries about the program is here: j.stasik@ukirt.hawaii.edu)
[Image credit: UKIRT / University of Hawaii Institute for Astronomy]
When we look out at the Universe today, we see that it's full of stars and galaxies. And yet, we can only see those stars and galaxies because the space between those galaxies and ourselves doesn't block that starlight before it gets to our instruments, observatories, telescopes, and eyes. But early on, that's an enormous problem: there is light-blocking gas and dust, and the record-holder for most distant galaxy ever discovered is still not a pristine, first-generation galaxy at all.
But there are new observatories and cutting-edge techniques that will reveal them, teaching us how the Universe grew up: from a collection of neutral atoms with no stars and galaxies at all to the structure-rich Universe we see today. Joining me on this special, bonus edition of the Starts With A Bang podcast (because don't we all need a bonus?) is extragalactic astronomer and PhD candidate Rebecca Larson from the University of Texas - Austin, in a rich conversation that takes us all the way back to the edge of the Universe as we can observe it.
Find out what lies at, and perhaps beyond, our current cosmic frontiers!
(Image credit: NASA, ESA, and J. Kang (STScI))
When we look out at the galaxies in the Universe, almost all of them have supermassive black holes at their centers: millions or even many billions of times more massive than our Sun is. Most of the time, these black holes are relatively quiet, but every so often, a black hole can be spotted emitting enormous amounts of radiation over a large range of the electromagnetic spectrum. These "active galaxies" come in many different flavors, from blazars to AGNs to quasars and many others, but they're very closely tied to both the age of the Universe and how rapidly a galaxy forms stars.
There's an awful lot that we've learned about these objects, and yet, still so many more mysteries to solve and uncover. This month, as the first of two podcasts, I'm so pleased to bring PhD candidate Alyssa Sokol, from the University of Massachusetts - Amherst, onto the program, as we enjoy a far-reaching conversation that takes us beyond the limits of what we know.
(Image credit: X-ray - NASA, CXC, R.Kraft (CfA), et al.; Radio - NSF, VLA, M.Hardcastle (U Hertfordshire) et al.; Optical - ESO, M.Rejkuba (ESO-Garching) et al.)
When it comes to gravitational waves, our terrestrial laser interferometers have provided us with unparalleled success in terms of direct detection. But they have some strong fundamental limits: their laser arms are short; their sensitivity is limited to low-mass, small-radius objects; the signals they detect last for mere seconds, at most. Most importantly, seismic noise, and even the fact that we live on a planet with tectonic plates, place restrictions on how sensitive we'll ever be able to get.
But in space, all of these stories change dramatically, and the upcoming European Space Agency mission LISA is aiming to open up our eyes to a realm of gravitational wave astronomy like we've never experienced before. On this edition of the Starts With A Bang podcast, we're joined by Dr. Ira Thorpe of NASA as we explore the future of gravitational wave astronomy in an entirely new realm: in space!
(Image credit: EADS ASTRIUM)
Even today, the Universe is forming enormous numbers of new stars: from various nebulae throughout our galaxy to mighty starburst galaxies where the entire galaxy is an enormous star-forming region. A decade ago, we were still trying to figure out how, when, and where stars formed throughout the Universe; today, we have that nailed down, but a whole suite of new questions and puzzles have arisen as a result of what we learned.
On this edition of the Starts With A Bang podcast, I'm pleased to welcome Indiana University astronomer Jennifer Sieben to the show, who specializes in the Universe's star-formation history and also works in astronomy outreach. She has a YouTube channel with astronomy vlogs: https://www.youtube.com/playlist?list=PLNgwz85_GjP_t2_HhUQ7BFj_S189sOPz1 Serves as her University's outreach coordinator for astronomy and is co-Editor-at-Large for a science blog: blogs.iu.edu/sciu/ And can be found here on Twitter: https://twitter.com/TARDISeeker
Come enjoy the spectacular story of the Universe's newborn stars today!
(Image credit: A Feild / STScI, 2002)
Dark matter is often thought of as the glue that holds the Universe together. With five times as much gravity due to this unseen form of matter as compared to normal, atom-based matter, it affects how galaxies and giant large-scale structures form in a tremendous, truly epic way. But depending on what the properties of dark matter actually are, we should get a very different Universe on smaller scales.
Is dark matter cold? Warm? Hot? And does it interact with itself, or is it truly invisible? Thanks to a fascinating new technique, we're learning more about this than ever before. Take a listen as we invite Dr. Anna Nierenberg onto the podcast to talk about how gravitational lensing is revealing dark matter substructure as never before, and how it might reveal these elusive properties of dark matter at long last as a result.
(Additional information: https://www.forbes.com/sites/startswithabang/2020/01/10/eight-new-quadruple-lenses-arent-just-gorgeous-they-reveal-dark-matters-temperature/ )
(Image credit: NASA, ESA, A. NIERENBERG (JPL), AND T. TREU AND D. GILMAN (UCLA))
When you look up at the sky, most of the points of light we see appear to be fixed. On night-to-night timescales, the distant stars and galaxies, with the exception of a few notable variables, appear to be relatively unchanged. But every once in a while, a spectacular event will occur, giving off a transient signal that outshines a typical star's brightness by factors of many billions. These events fall into many classes: supernovae, gamma ray bursts, and even more exotic events, and part of the fun is uncovering exactly what's going on as we discover these new classes of objects for the first time.
Scientist Anna Ho, PhD candidate at Caltech, is right on the cutting edge of that frontier, and brings us an insider's look at this exciting and rapidly evolving field. Come get the latest on what we know and what we're still learning about the cataclysmic deaths of stars!
(Image credit: Bill Saxton (NRAO/AUI/NSF))
One of the great challenges for astronomy is to determine, in gory detail, how stars are formed from a mere cloud of molecular gas and dust. Although the general picture is simple, where gravitational collapse leads to protostars that ignite nuclear fusion in their cores, the actual environments where these stars are born have many competing factors at play. Gravitational collapse is only one of them, joined by thermal heating and radiative cooling, magnetic fields and hydrodynamics, as well as stellar winds, ultraviolet radiation, and feedback from a variety of sources.
Here to help us disentangle what's important, where, and when is Ph.D. candidate Mike Chen, an astrophysicist specialized in the formation of stars at the University of Victoria. If you've ever wondered how we actually form stars in our Universe, this edition of the Starts With A Bang podcast is for you!
(Image credit: ESA and the Planck Collaboration.)
How many planets are out there in the Universe? How many stars have planets, and what kinds of planets do stars of various types have? How close are we to doing direct imaging, finding whether some of our Earth-like planets are potentially habitable or even inhabited? Are Super-Earths a real thing, or are all of the ones larger than our world more Neptune-like than we care to admit?
We've answered a whole slew of questions about exoplanets that we didn't even know to ask a decade or two ago, and there's so much more happening right now as well as on the horizon. Come get the scoop on the latest Starts With A Bang podcast, featuring the incredible Dr. Jessie Christiansen of NASA's Exoplanet Science Institute!
(Image credit: NASA / TESS)
The history of astronomy is a history of receding horizons. As we improve our optics, our instruments, and our observing techniques, we can reveal progressively more of the Universe than we've ever seen before. As the 2020s dawn on us, we're preparing to jump from 10 meter-class observatories, which are presently the largest in ground-based optical telescopes, to 30 meter-class ones, with approximately thrice the resolution and ten times the light-gathering power. There's a tremendous suite of cosmic stories to discover, but the only one of the 30 meter-class observatories to be built in the Northern Hemisphere is facing a tremendous controversy that's been decades in the making. What are the next steps towards building the Thirty Meter Telescope?
The latest edition of the Starts With A Bang Podcast features the TMT's vice president for external relations, Dr. Gordon Squires, and you won't want to miss it!
(Image credit: Thirty Meter Telescope Collaboration)
Have you ever wondered what the first moments of our Universe were like? Not just going back towards the hot Big Bang, but at the very first fractions of a second that come after, during, and even before the Big Bang occurs?
It was my pleasure to get to speak to Dan Hooper, astrophysicist, professor, and author of the new book At The Edge Of Time, which is my favorite popular science book of 2019. (Pick up a copy here: https://amzn.to/2XReiGG)
In this fascinating hour+ conversation, we cover topics like dark matter, inflation, and what not only 21st century physics but even 30th century physics might hold. Don't miss it!
(Image credit: Princeton University Press / Dan Hooper.)
What lies out there, in the outer Solar System, beyond the orbit of the last known planet? Up until 1992, you would have said Pluto and its moon (maybe "moons" if you were willing to speculate), but even the existence of the Kuiper belt was doubted by many. Of course, all of that changed with the discovery of many different objects, including the more-massive-than-Pluto world discovered in 2003: Eris. We quickly realized that Pluto was not unique, but one member of a distinct class of objects thoroughly different than the planets. In 2006, we created the "dwarf planet" classification for non-planetary objects that still were Pluto-like.
But more recently, a compelling but controversial idea has emerged: the idea of a Planet Nine that is more massive than even Earth, but lies hundreds of times farther away that we are from the Sun. Both of these achievements, the theorizing of Planet Nine and the Pluto-killing discovery of Eris, come courtesy of the same planetary astronomer: Mike Brown. Dive into a fascinating conversation with him and me right here on the 50th edition of the Starts With A Bang podcast!
(Image credit: Caltech/R. Hurt (IPAC))
The Large Hadron Collider, located at CERN, is the most powerful particle accelerator and collider in human history, and the detectors that observe the collisional debris are the most sensitive and comprehensive ever constructed. With this powerful new tools, physicists discovered the Higgs boson earlier this decade, and continue to probe the frontiers of the known Universe.
Currently undergoing upgrades, the LHC has only collected, to date, 2% of the eventual data it will wind up collecting. Meanwhile, physicists are already planning for the future, looking to build a next-generation collider capable of probing the frontiers beyond the LHC's reach.
Yet many detractors, dissatisfied with the motivations for pushing these boundaries forward, are working to obstruct this tremendous, civilization-scale endeavor. My guest this month on the Starts With A Bang podcast is Dr. James Beacham, a scientist who works as a member of CERN's ATLAS collaboration. In a far-ranging discussion, we talk about the LHC and beyond as we face an uncertain but potential-filled future for particle physics. This is one discussion you won't want to miss!
(Image credit: CERN / Maximilien Brice and Julien Marius Ordan)
Earlier this year, 2019, the Event Horizon Telescope collaboration revealed the first image that directly showed the existence of an event horizon around a black hole. This image, constructed from many petabytes of data from telescopes observing the same target, simultaneously, from all across the Earth, provided a breathtaking confirmation of Einstein's relativity in a realm where it had never been tested before. But that's just one image of one black hole at one particular moment in time, and there's so much more to come from the Event Horizon Telescope.
This month, we're so fortunate to sit down with EHT scientist Sara Issaoun, who takes us through the past, present, and future hopes for the Event Horizon Telescope and how it hopes to answer humanity's biggest questions about black holes.
(Image credit: APEX, IRAM, G. Narayanan, J. McMahon, JCMT/JAC, S. Hostler, D. Harvey, ESO/C. Malin)
What do we really know, and what mysteries are left to solve, about the outer worlds of our Solar System, and about the gas giant and ice giant worlds found throughout the Universe? Remarkably, if you had asked this same question 30 years ago, we would have had a quaint story about how planets form and why our Solar System has the planets it does, and we assumed that these rules would be extended to all solar systems in the galaxy and Universe. But with the deluge of exoplanet data, accompanied by better observations and simulations of our Solar System, that old story isn't even the half of it.
I'm so lucky to get to interview Heidi Hammel for this edition of the podcast, who, as a bonus, was the lead investigator on the Hubble Space telescope when Comet Shoemaker-Levy 9 impacted Jupiter back in 1994! Come listen to one of my favorite interviews ever today!
(Image credit: NASA/Voyager 2)
We know that there's more to the Universe than we presently know. As successful as the Standard Model may be, it cannot describe everything we observe to be true about the Universe. Neutrinos oscillate from one flavor into another, and must have a non-zero mass, but we don't understand why or how. Dark matter has an overwhelming suite of astrophysical evidence that points towards its existence, but we have no direct evidence for the type of particle it might be.
What do we do about these puzzles? We perform the best experiments we can to try and probe, identify, and constrain the novel physics that might be responsible for these unexplained phenomena.
This month, I'm so pleased to chat with Doctor Laura Manenti, postdoctoral research associate at NYU Abu Dhabi and a researcher on the XENON1T and the Proto-DUNE experiments. Take a dive into the world of experimental particle physics on the latest Starts With A Bang podcast!
(Image credit: Enrico Sacchetti.)
With all the planets out there in the galaxy and Universe, it's only a matter of time and data until we find another one with life on it. (Probably.) But while most of the searches have focused on finding the next Earth, sometimes called Earth 2.0, that's very likely an overly restrictive way to look for life. Biosignatures, or more conservatively, bio-hints, might not only be plentiful on worlds very different from our own, but around Solar Systems other than our own. Earth-like worlds, in fact, might not even be the most ubiquitous places for life to arise in the Universe.
I'm happy to welcome scientist Adrian Lenardic onto the Starts With A Bang podcast, and explore what just might be out there if we look for life beyond our idea of Earth 2.0!
(Image credit: JPL-Caltech/NASA.)
One of the biggest conundrums in the Universe surrounds the question of how quickly the Universe is expanding. Questions like what is the Universe made of, how old is it, what is it's ultimate fate, etc., absolutely depend on this. For generations, we argued over the details of this, seeming to have finally reached a consensus in 2001 with the Hubble Key Project's results: 72 km/s/Mpc, with an uncertainty of about 10%. But the modern results, as of 2019, seem to depend on how you measure it. Some teams are consistently getting 67 km/s/Mpc, while others get 73-74 km/s/Mpc, with uncertainties that don't overlap.
This may not be a controversy, but rather a clue, and Nobel Prizewinner and co-discoverer of dark energy Adam Riess joins me on this special edition of the Starts With A Bang podcast. Don't miss it!
(Image credit: NASA / GSFC)
When we think about finding planets in the Universe, we typically look for ways to detect them as they orbit their parents stars, either affecting their star's position or velocity, or blocking or reflecting a certain portion of their light.
But what about the planets that are too small to be detected that way? What about the planets whose effects are imperceptible? And what about the rogue planets: the ones that no longer (or perhaps never did) orbit a star of their own?
Well, they're not doomed to be invisible! In fact, we can measure and characterize them extremely well, through the power of gravitational microlensing. This isn't some pipe dream of science fiction that may someday come to fruition; it's real, current science that expects a tremendous explosion of planetary discoveries with WFIRST's launch in the mid-2020s. Come find out what the future of this fascinating scientific field holds as we launch into a tremendous conversation with researcher Savannah Jacklin, as we explore the microlensing Universe!
(Image credit: NASA's Exoplanet Science Institute / JPL-Caltech / IPAC)
So, you want to know about black holes, including how we're seeing them, what happens when you fall into them, what our future plans for direct and indirect detection are, and how scientists are answering some of the biggest questions about them today?
It's a fascinating story about some of the most mind-blowing objects in the Universe. Please welcome Assistant Professor of Astronomy and Physics at the University of Mississippi, Dr. Leo C. Stein, to the show, and enjoy a 1 hour+ conversation where we explore some of the deepest concepts in cutting-edge physics and gravitational wave astronomy!
(Image credit: Northwestern Visualization/Carl Rodriguez)
After the Big Bang, it took only a few hundred thousand years for the Universe to form neutral atoms. But it took tens or even hundreds of millions of years for the first stars to turn on, and a whopping 550 million years for those neutral atoms to all become reionized by that starlight once again.
Believe it or not, we can measure not only the starlight coming from the stars that do form through the now-infrared light they emit, but also the neutral atoms themselves through the power of 21-cm astronomy. I'm joined this week by Dr. Elizabeth Fernandez, research astronomer, science communicator and podcaster extraordinaire on her show, SparkDialog. (Check it out, here: http://sparkdialog.com/)
How did the Universe grow up to be the way it is today? Take another spectacular step on the latest edition of the Starts With A Bang podcast.
One of the great goals in our study of the Universe is to see past the currently-known frontiers. That means going farther, to greater and greater distances. It means going fainter, to smaller and less-easy-to-see objects. It means going to earlier times and less-evolved conditions. And it means detecting more of the Universe than we've ever seen before. Our goal is the most ambitious one you can imagine: understanding what the Universe was like when it was born, how it grew to be the way it is today, and where it's headed in the future.
One huge step that we only took this decade was to detect the first pristine matter left over from the Big Bang, before any stars or galaxies formed from it. A second, that we're taking today, is to try and create a better space-based observatory than Hubble or even James Webb.
On this edition of the Starts With A Bang podcast, we talk about both of these issues with astronomer and chief scientist at the Keck Observatory: John O'Meara. Enjoy!
Is there intelligent life out there in the Universe beyond planet Earth? If so, are they technologically advances, can they hear us, and are they broadcasting in ways that we could possibly detect them?
In the absence of their arrival on Earth, you might think that there's no surefire way to know. But the scientists working hard on SETI, the Search for ExtraTerrestrial Intelligence, sure are trying their best. By listening to the Universe at large (and our galaxy in particular), they're hoping to uncover the answer to perhaps the ultimate question: whether there's a civilization out there that humanity might hope to make contact with, and that could perhaps be our ally in uncovering the great mysteries of the Universe.
I'm so pleased to welcome astronomer and senior scientist at the SETI Institute, Seth Shostak, onto this edition of the Starts With A Bang Podcast!
In 2017, the incredible happened: for the first time in history, we were able to identify an object passing through our Solar System that originated from outside of it! Interstellar interloper 'Oumuamua was originally designated as a comet, then as an asteroid, and then as a new class of object: one of interstellar origin. It's a fascinating object that's the first of its kind, and much has been said about its composition, properties, and possible nature. But, unfortunately, the most famous of those "nature" discussions was from Schmuel Baily and Avi Loeb of Harvard, claiming that it could be due to aliens.
Is that plausible? Is that even science? My guest for this edition is astrophysicist Paul Matt Sutter, author of the new book Your Place In The Universe, and we have an almost-hour-long discussion that goes to some fantastic and unexpected places. You won't want to miss it!
Find Paul online on Twitter https://twitter.com/PaulMattSutter, Video: http://www.pmsutter.com/shows/askaspaceman/, Book: Your Place In The Universe https://amzn.to/2DCysNj.
Our Solar System formed some 4.6 billion years ago from a molecular cloud that collapsed. Our proto-Sun formed along with a protoplanetary disk that eventually evolved into the Solar System we have today, complete with the inner, rocky planets, an asteroid belt, the gas giants and their moons and ringed systems, and then the outer Solar System.
Those outer regions sure are interesting, and it's only over the past 3 decades we've really started to learn about them in earnest. I had the opportunity to speak with outer Solar System specialist Michele Bannister, and she agreed to be this month's guest on our podcast. Oh, did an exciting discussion ensure, and we've got over an hour of knowledge for you!
What's the status on how the Solar System formed, on Planet Nine and its alternatives, and what the prospects are for taking the next major steps? Find out on this edition of the Starts With A Bang podcast!
Find Michele here at her current research location: https://pure.qub.ac.uk/portal/en/persons/michele-bannister(c83612a1-80b4-4f78-a9f2-85efe0347d3a).html And on Twitter @astrokiwi: https://twitter.com/astrokiwi?lang=en
I'm so pleased to welcome Dr. Erin MacDonald to the Starts With A Bang podcast, as we discuss the future of Gravitational Wave astronomy. From pulsars to merging black holes, to kilonovae to hopes of observing gravitational wave signatures from the earliest moments of the Universe, we cover a whole lot of astrophysics, cosmology, and experimental hopes for the near future in this burgeoning new field of astronomy.
The future of gravitational wave science is so bright, even without the collection of any light. Come learn all about it today!
Find Dr. Erin MacDonald online here: Website: www.erinpmacdonald.com YouTube: www.youtube.com/c/erinmacdonald
There's been a lot of speculative ideas put forth about the Multiverse, and I dare say that a great many of them are nothing more than wishful thinking. But that doesn't mean the Multiverse itself is ill-motivated at all. Rather, if you take two of our best theories that have been well-confirmed in a wide variety of different ways, you're going to find that you arrive at a bizarre but unavoidable picture: one of an inflating spacetime, eternal to the future, where regions that look like our Universe, complete with a hot Big Bang, are spawned continuously.
The evidence might not be there, observably, to confirm or deny the existence of a Multiverse. But as a theoretical consequence, it certainly has a motivation that's far stronger than practically anyone realizes. Here's the cosmic story.
The Universe, today, is expanding and cooling, as the volume of the Universe increases while the number of particles within it remains constant. If you extrapolate forwards in time, the Universe gets sparser, less dense, and closer to being completely empty. But if you extrapolate back in time instead, the Universe gets hotter, denser, and smaller in volume. Eventually, if you didn't stop yourself, you'd go all the way back to a state of infinite density, where all the matter was packed into a single point: a singularity. This was where, when it was first formulated, the idea of a Big Bang singularity came from, and the idea that space and time had a beginning.
Yet we no longer believe that to be true! Why not? Come find out on this edition of the Starts With A Bang podcast!
Have you ever wondered what's out there in the Universe, on the largest scales, beyond what we can even observe? Or what lies down below the tiniest distance scales we've ever probed? Is there a smallest fundamental length scale in the Universe, like the Planck scale, or can we go down even farther? Is space discrete or continuous? And is the Universe fundamentally blurred; can we even distinguish?
Thinking about the limits of space, on both small and large scales, is a mind-bending game to play, but we're up to the challenge on this latest edition of the Starts With A Bang podcast!
There are three very different ways humanity is searching for alien life beyond Earth. We can directly search the various planets and moons in our Solar System for past or present biological signatures simply by sending decontaminated probes, and looking for the evidence in situ. We can indirectly look at distant worlds around other stars, searching for the characteristic changes to the atmosphere and surface that life would bring. And, most optimistically, we can search for intelligent signatures created, perhaps willfully, by a technologically advanced alien species. These are our three hopes for finding alien life, and we're actively pursuing all three. Here's how the different searches work, along with some speculation about what we're likely to find, and what motivates us to look!
There are some incredibly big questions that humanity has been asking about the Universe since we first began looking upwards: what is the Universe like, how did it get to be this way, where did it all come from, and what is its eventual fate? There were huge advances that were needed in order to answer these questions, such as understanding what the Universe was made of, how fast it was expanding, and what the laws governing it were. But once we know that, not only can we answer these questions, but we can do it with a single equation. It's known as the First Friedmann equation, and I call it the most important equation in the Universe.
Find out why on this edition of the Starts With A Bang podcast!
In memory of Stephen Hawking's life, I've decided to share the physics behind his greatest discovery: Hawking radiation. For a long time, in the context of relativity, we thought that black holes were static, unchanging objects defined only by their mass, charge, and angular momentum. A number of developments led us to understand that black holes needed to have entropy, temperature, and therefore, they needed to radiate. But Hawking was the one to put that puzzle together, and describe the physics of the radiation and its consequences for black holes.
It goes much further than that, with the famed (and still unresolved) black hole information paradox arising from his work. Who will be the ones who take the next great leap? Come learn what we know and where the frontiers are on this special edition of the Starts With A Bang podcast!
When you fall inside the event horizon of a black hole, there's no escaping, no matter what you do or how you accelerate. Even if you travel at the Universe's speed limit, the speed of light, there's simply no way to get any closer to the exit. Instead, scientists say, you have no choice but to fall inevitably towards the singularity at the center. But why must you arrive at a singularity? Couldn't you wind up at some degenerate object instead?
We don't think so, and here's the science behind why. Find out what's at the center of a black hole today!
A simple, innocent question that I received had me thinking for days about how to answer it. The question?
"If humans were made in God's image, whose image were aliens made in?"
There's so much to say from a science perspective about how humans were made, and how aliens might be made, that I couldn't resist giving it my absolute best! Do you agree? Comment below!
Ever wonder about the biggest questions that there are? You know the ones I mean: about what is the Universe, where does it come from, and what is its fate? For millennia, these were questions for poets, philosophers, and theologians. Yet, despite all the "answers" that they offered, there was no way to test or verify whether they were correct.
Enter science.
After countless lifetimes struggling mightily with these, we have the answers, and they're spectacular. What do we know? How do we know it? And why is science so powerful at giving these answers? Find out, on this latest edition of the Starts With A Bang podcast!
Ever dream of traveling back in time? According to all the laws of special relativity, all you can do is travel forwards through time, controlling your rate by controlling your motion through space. But in General Relativity, the curvature of spacetime allows you to play with those rules a little more flexibly.
You can make it back in time, but you still can't kill your own grandpa before your parents were conceived. Find out why on this edition of the Starts With A Bang podcast!
Video version (for the first time): https://www.youtube.com/watch?v=PhCxtdxa8nI
Our current best theories describing the Universe, general relativity for gravity, quantum field theory for electromagnetism and the nuclear forces, do a fantastic job independently and together. But there are fundamental questions that go unanswered if we take these as the final answers. What happens to the gravitational field of an electron passing through a double slit? What happens to the information on a black hole's surface when it decays? And what happens close by a gravitational singularity? Without a quantum theory of gravity, we can't know.
Yet we're on a path to try and figure it out! Where are we, and how far do we have to go? Find out, on this edition of the Starts With A Bang podcast!
Right around one year from today, the James Webb Space Telescope will launch to a position 1.5 million kilometers away from Earth, deploying into a quasi-stable orbit around the L2 Lagrange point. Its magnificent, 5-layer sunshield will unfold, allowing it to passively cool down to temperatures cold enough to turn nitrogen into a liquid. Beyond that, it will have on-board coolant taking it down to 7 Kelvin, allowing us to observe light that's 50 times as long as the wavelengths the human eye can see. The gold mirrors are ideal for reflecting infrared light, and will allow us to view the Universe as never before.
This isn't the "next Hubble" as some are saying, but rather the first James Webb! Here's what's in store, and what makes it so magnificent.
On August 21, 2017, a total solar eclipse occurred over the continental United States for the first time in nearly 39 years, when half the current US population wasn't even born. For many of us, it was our first opportunity to ever experience a sight like this for ourselves, and not only lived up to the hype, it was something that even a scientist couldn't fully anticipate. Here's a first-person account of what the experience was like, and how to enjoy it to the fullest, yourself, the next time one comes around!
On August 21, 2017, a coast-to-coast total eclipse across the United States will occur, the first one in 99 years. As the Moon's shadow hits the Earth and speeds across it, there's so much to see and enjoy, but only if you're prepared. What should you look for? Where should you go? How can you stay safe? And what's the science behind it?
Come get the full story on the latest edition of the Starts With A Bang podcast!
More information: https://www.forbes.com/sites/startswithabang/2017/07/27/the-sights-safety-and-science-of-the-great-american-eclipse/
At a fundamental level, everything we know of in this Universe is made of the same few fundamental particles: quarks, gluons, electrons and photons, which combine to give us atoms, which in turn make up all the molecules, cells, organs and living creatures inhabiting our world today. But how do we go from these tiny scales where everything looks so similar to the huge diversity of what exists at a larger, more macroscopic scale?
The secret is encoded in a single quantum rule that governs how it all works: the Pauli exclusion principle. Come get the scoop here on the latest Starts With A Bang podcast!
Have you ever wondered how the Universe will end? In the far future, everything that we know, see, measure and perceive today will someday decay away, becoming something very different from what we know it as today. The Earth will cease to harbor life, the Sun will die, the galaxies will merge and recede, and eventually everything will fade to black. But beyond that, space itself will push everything apart, stellar remnants will get ejected, and even the most massive objects at all will decay into nothingness.
In just 20 minutes, you can experience the entire future of everything to come.
Is time travel possible? Of course it's inevitable in some sense, as we always move through the Universe at the "boring" rate of one second per second. But what about traveling into the future? If we go, can we ever come back? And what about back in time? Would it be possible to alter the past, or revisit a historical event as an observer? The mathematics of relativity opens the door to a lot of possibilities, but the physical Universe has a lot to say about it, too.
In 1930, Clyde Tombaugh discovered Pluto: our Solar System's ninth planet. For over 60 years, the Plutonian system was the only one known beyond Neptune, and Pluto retained its planetary status for all that time despite its diminutive size. Yet an explosion of exoplanets and of other Trans-Neptunian Objects within our own Solar System beginning in the 1990s meant that we'd need to reconsider what it means to truly be a "planet". The debate still rages today, but astronomers agree: when it comes to the planetary club, Pluto simply doesn't belong. Here's why!
Our Universe was born pristine, with no stars, galaxies, molecules or even stable atoms, some 13.8 billion years ago. Yet today, we're filled with all the complex structure we see today, including with planets, organics and even something as complex and differentiated as a human being. So how did we get here? We had to form stars and galaxies, and evolve the Universe to a point where the raw ingredients to make us existed in great enough abundances and in the right conditions. There are some steps we're still learning about in this story, including how the very first stars came to be. Want to learn about it? Find out on this latest Starts With A Bang podcast!
The discovery almost 100 years ago that the Universe was expanding was a revolution for science, for cosmology and for our conception of existence. Hubble discovered what Einstein's couldn't imagine, and after that, the race was on to learn exactly what those observations meant for our cosmic origins. After decades of controversies, we now have a better picture of our Universe than ever before, yet questions remain. What will be the ultimate answer? Find out the possibilities, and what the limits of our knowledge tell us is possible, on this edition of the Starts With A Bang podcast!
Black holes are incredibly massive objects that are so dense that, from within a given region of space, nothing can escape, not even light. Yet it's arguable that from our point of view, nothing can escape our observable Universe. Moreover, even though our Universe is huge, it's also incredibly massive, and since it's expanding, it was denser and smaller in the past. Could our Universe be the inside of a black hole? And do we have evidence either supporting this or ruling it out? Find out on the latest episode of the Starts With A Bang podcast!
Ever since we first uncovered the quantum nature of our Universe, humanity has struggled to interpret it. Is there a wavefunction that collapses? Is it the quantum operators themselves that change? Does the end state evolve? Or are there an infinite number of parallel Universes that correspond to all the possible outcomes? This last possibility may actually be plausible, and this podcast is a deep dive into the adventure that ensues if they're real. But beware, there are a lot of assumptions needed to get there!
Did you hear the news, that it isn't "billions and billions" anymore, but that there are TWO TRILLION (or 2,000,000,000,000) galaxies in the observable Universe? Come get the science behind this amazing story, including how we know, what it means and what we'll even have the potential to learn in the near future.
For thousands upon thousands of years, we didn't know whether the other stars in the Universe were even like our Sun, much less whether they had planets around them like we find in our Solar System. Over the past 25 years, however, that question has not only been answered, but we've discovered thousands of confirmed planets. Even more exciting, we've found that the star systems out there are similar to our own in some ways but tremendously different in others, and that there are already more than 20 rocky planets known that are at the right distance to have liquid water on their surface, given Earth-like atmospheres. This includes the closest star to our own: Proxima Centauri, whose planet 'Proxima b' just might be our first step into the Universe beyond our Solar System. Enjoy!
Our Universe has been expanding and evolving since the hot, dense, expanding state known as the Big Bang first came to be. But there was a "day without yesterday," where the Big Bang occurred at a moment in time! Was that the birth of space and time itself? Or was there a pre-existing state that came before and gave rise to the Big Bang? Come find out the evidence that's led us to our greatest conclusions about the very beginning of where everything came from!
While there are presently more than ~10^23 stars in the Universe shining today, each one of them is fated to live only for a finite amount of time. While more and more will continue to form, we're already past the point of peak star formation in the Universe. How long will we have until, for the last time, the Universe's last star goes out?
Find out on this edition of the Starts With A Bang podcast!
Ever since humanity had the thought that the distant, twinkling stars might be Suns like our own, with their own planetary systems and chances at life, we've dreamed of extending humanity's reach to the galaxy and beyond. What are our actual chances of doing so, technologically, scientifically and practically? This podcast -- based on an exclusive interview with Larry Niven -- explores what's possible.
How will the Universe end? Will it recollapse in on itself, ending in a Big Crunch? Will it expand forever, ending in a Big Freeze? Or will it tear itself apart, ending in a Big Rip?
With the discovery of dark energy, we finally think we know, but there's always more science to be done, more possibilities to consider, and new evidence to look for to help point the way.
Could there be a ninth planet in our Solar System, farther out than Neptune? Recent evidence points to a tantalizing possibliity, and searches are underway to look for it. Here's the science behind the full 'Planet Nine' story, in one amazing, easy-to-follow podcast!
The Hubble Space Telescope has just shattered the record for most distant galaxy in the Universe. How did we break this record, and what do we expect to find even farther back?
In February of 2016, less than six months after first becoming operational, LIGO (the laser interferometer gravitational wave observatory) announced the first-ever direct detection of gravitational waves. What are they? What does it mean? What did we learn? And what can we do with them now that we know they exist? All this and more on this month's Starts With A Bang podcast!
In 1930, Clyde Tombaugh serendipitously discovered Pluto: the first object in our Solar System out past Neptune. For 48 years, it was the only object known out there, until Charon -- its giant moon -- was discovered. But the 1990s brought with it a slew of Kuiper Belt objects, and in 2006, Pluto was officially demoted to a "dwarf planet." But also in 2006, NASA's New Horizons mission was launched: the first dedicated mission to the outer Solar System. In 2015, it flew by both Pluto and Charon, discovering two vastly different worlds. Here's what we've learned.
Everywhere we look in the Universe, we find that planets, stars, galaxies, and even the gas between them are all made of matter and not antimatter. Yet as far as we know, the laws of nature are symmetric between matter and antimatter: you can't create or destroy one without the other. So how did our Universe get to be the way it is? Come right up to the frontiers of our scientific knowledge and have a listen!
Although it's been only 13.8 billion years since the Big Bang, we can see objects as distant as 46.1 billion light years away. How is this possible? Ethan Siegel explains in the second Starts With A Bang podcast. Plus, how to see Comet Catalina in the December skies, and why it's on its way out of the Solar System forever.
This podcast is free to download and distribute in perpetuity thanks to the support of our Patreon donors at www.patreon.com/startswithabang?ty=h
In the first inaugural Starts With A Bang podcast, astrophysicist Ethan Siegel discusses the latest evidence for water on Mars, what it means for Earth and potential life on the surface, as well as other topics. Guest (and Patreon supporter) Maciek makes an appearance, and we discuss the future of physics and speculate on what the next great advance might be.
This podcast is free to download and distribute in perpetuity thanks to the support of our Patreon donors at https://www.patreon.com/startswithabang?ty=h