Stars | Astronomy Cast: Recent Episodes
Stars | Astronomy Cast
The next great eclipse is upon us, with viewers across North America witnessing the moon passing in front of the Sun. It’s an amazing experience, but also an opportunity to do science. Let’s talk about what we can learn from this momentous event.
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Solar cycle 25 is shaping up to be a doozy, with plenty of flares and coronal mass ejections blasting off the Sun. As the solar activity continues to rise, how are things shaping up?
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After the cosmic microwave background radiation was released, the Universe returned to darkness, cloaked in this clouds of primordial hydrogen and helium. Gravity pulled these vast clouds into the first stars, and then the first galaxies. This is Cosmic Dawn, and JWST will help us probe this mysterious time.
In 2017, astronomers detected the gravitational waves and electromagnetic radiation from colliding neutron stars. This had been long theorized as one of the causes of a certain type of gamma-ray burst. By studying the event and its afterglow, astronomers have learned a tremendous amount about the formation of the heaviest elements in the Universe.
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Last week we talked about rogue stars. This week we’re going to take things up a notch and talk about an even more extreme event. Rogue black holes. Astronomers recently discovered a supermassive black hole on an escape trajectory, leaving newly forming stars in its wake. It’s wonderful, terrible, nightmare fuel.
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Most stars in the Milky Way are trapped in here with us, doomed to orbit around and around and around. But a few have found a way out, an escape into the freedom of intergalactic space. How do stars reach escape velocity, never to return?
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The Cosmic Microwave Background Radiation tells us so much about the Universe. After that era, the Universe went dark. Then, as gas pulled together into the first stars and eventually galaxies, light returned, beginning the Age of Reionization.
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Show Notes241st AAS Meeting (AAS)
JWST (NASA)
Hubble Space Telescope
What is the Cosmic Microwave Background? (Universe Today)
Epoch of Reionisation (MWA Telescope)
What Is the Big Bang? (NASA Space Place)
What are photons? (Live Science)
How the Cosmic Dark Ages Snuffed Out All Light (Quanta Magazine)
Energy Levels of Electrons (SDSS)
Ionization (Energy Education)
Population III stars: The Universe’s ultimate reclusive pop stars (KIPAC)
Dwarf Galaxy (ESA/Hubble)
The Pillars of Creation (NASA)
Spitzer Space Telescope views cosmic bubbles in infrared (BBC Sky at Night)
Messier 42 (The Orion Nebula) (NASA)
Quasar (ESA/Hubble)
What is ‘red shift’? (ESA)
What is Gravitational Lensing? (CFHTLens)
Quasars, the Lyman Alpha Forest, and the Reionization of the Universe (Astrobites)
Lyman-alpha_line (ChemEurope)
Astrophysical Classics: Neutral Hydrogen in the Universe, Part 2 (Astrobites)
Peter Gunn (TV Series 1958–1961) (IMdB)
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The Sun is a third-generation star, polluted with the metals from long-dead stars. Astronomers have also discovered second-generation stars, with very low metallicity. But theories suggest there must be a first generation, with stars made from only pure hydrogen and helium. Can we ever find them?
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Show NotesThis episode is sponsored by BetterHelp. Give online therapy a try at betterhelp.com/ASTRONOMY and get on your way to being your best self.
NASA Artemis (NASA)
JWST (NASA)
DART (JHUAPL)
Chinese space station epitome of aerospace workers’ wisdom: designer (CGTN)
InSight Mission – NASA’s InSight Mars Lander (NASA)
Overview | Sun (NASA)
Stars – Stellar Populations (Astronomy Online)
What is stellar magnitude? (EarthSky)
Population I (Swinburne University)
Population II (Swinburne University)
Population III (Swinburne University)
What is a globular cluster? (EarthSky)
Two planets around Kapteyn’s star: a cold and a temperate super-Earth orbiting the nearest halo red dwarf (MNRAS Letters)
Pair-Instability Supernovae: What might they look like? (Astrobites)
Gamma radiation (ARPANSA)
Hydrostatic Equilibrium (Swinburne University)
Positron (Swinburne University)
Potential First Traces of the Universe’s Earliest Stars (NOIRLab)
Quasar (Swinburne University)
Gravitational Lensing (Hubblesite)
PDF: First Stars and First Light: The Epoch of Reionization (NSF)
What is the Cosmic Microwave Background? (Universe Today)
New insight of AGC 198691 (Leoncino) galaxy with MEGARA at the GTC (MNRAS)
Elemental Abundances (Center for Astrophysics)
Hubble Space Telescope
American Astronomical Society
241st AAS Meeting (AAS)
Supermassive Black Hole (Swinburne University)
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Moons orbit planets, planets orbit stars, stars orbit within galaxies. It’s orbits all the way down. But occasionally objects can receive a powerful kick that sends them off on a journey, never to return.
PART II
PART III
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Show NotesSuperman (DC Comics)
Iron Man (Tony Stark) (Marvel)
Conic Sections (Math is Fun)
Parabola (Math is Fun)
Hyperbola (Math is Fun)
Ellipse (Math is Fun)
Ballistic Trajectory (Universe Today)
FAQ – Earth (Planetary Science Institute)
Escape Velocity (Let’s Talk Science)
Spitzer (Caltech)
The Three-Body Problem (Scientific American)
PODCAST: Ep 102: Gravity (Astronomy Cast)
In Depth | Oort Cloud (NASA)
Overview | Comets (NASA)
Types of Comet (CometWatch)
In Depth | Oumuamua (NASA)
Ukrainian Astronomers Discover ‘Exocomets’ around Another Star (Scientific American)
The Solar System may have lost the original “Planet Nine” (Inverse)
Slingshot Star? (Science Magazine)
JOURNAL: A search for runaway stars in 12 Galactic supernova remnants (Astronomical Notes)
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Well, this is it, we’re finally going to talk about the James Webb Space Telescope. After decades of development, delays and budget creep, the powerful infrared observatory is at its final home at the L2 Lagrange Point. Yesterday we saw the first scientific images from the telescope, and according to Pamela’s rules, we’re finally allowed to talk about it.
All the waiting is over, we've finally seen the image of the event horizon from the supermassive black hole at the heart of the Milky Way. Today we're going to explain the picture, and what's next for the Event Horizon Telescope.
We've always assumed that we lived in a perfectly normal system with a normal star and normal planets. It's all... normal. But with our modern understanding of billions of stars, just how normal is our Sun, anyway?
We think of space as a vacuum, but there are regions of different density. There are winds blowing from stars and other objects that clear out vast bubbles in space, and look absolutely fantastic in pictures. And might have been critical for Earth to even exist in the first place.
As astronomers look out across the Universe, they see various objects spewing jets of material light years into space. What causes these jets, and what impact do they have on the Universe.
Pulsars are the rapidly spinning degenerate husks of dead stars, turning hundreds of times a second. But they're also handy clocks, spinning with such certainty and accuracy that astronomers can use them for all kinds of stuff. We might even use them to navigate the cosmos.
Once again, it's time to take a look at the Sun. You know, ongoing thermonuclear explosion of fusing hydrogen that's right over there. Fortunately, there's a fleet of spacecraft and ground observatories ready to give our best ever view of the Sun.
Stars often come in groups of two or more. And if they're orbiting close enough to each other, one star can feast on the other. And when that happens, well, mayhem ensues.
This year's Nobel Prize in Physics was awarded to three brilliant researchers who worked out some of the secrets of black holes. Today we're going to talk about the chain of discoveries that led to this award.
Don't ever accuse us of not comprehensively covering every kind of exploding star. This week we gather up all the leftover ways that stars partially or fully explode, or don't. Probably. Enjoy.
You'd think that a white dwarf star is the end of a stellar life. It's all downhill from there. A long, slow cool down towards the end of everything. But in some situations, even dead stars can get exciting again, briefly becoming some of the brightest objects in the Universe. And just maybe, the last exciting thing that ever happens in the Universe.
I’ve got some bad news for you: stars die. At some point in the next few billion years or so, our Sun is going to start heating up, using up all the fuel in its core, and then eventually die, becoming a white dwarf. It will then slowly cool down to the background temperature of the universe, becoming a black dwarf.
White dwarfs are usually about 60% the mass of the Sun, so it was a bit of a surprise when astronomers found one that was almost exactly twice that. What happens when white dwarfs merge? Download MP3| Download Raw Show with Q&A| Show Notes | Transcript Show Notes White Dwarfs: Compact Corpses of Stars (Space.com)White […]
You might be surprised to hear that we’ve never done an episode of Astronomy Cast featuring Betelgeuse. Well, good news, this is that episode. Let’s talk about the star, why it might be dimming, and what could happen if it explodes as a supernova.
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Show Notes Transcript Transcriptions provided by GMR Transcription Services
Fraser Cain: Astronomy Cast, Episode 560. Betelgeuse.
Pamela Gay: Betelgeuse, Betelgeuse.
Fraser Cain: Welcome to Astronomy Cast. Welcome to Astronomy Cast. Our weekly facts-based journey through the cosmos where we help you understand not only what we know but how we know what we know. I’m Fraser Cain, publisher of Universe Today. With me, as always, is Pamela Pamela Gay, a senior scientist for the Planetary Science Institute and the Director of Cosmo Quest. Hey, Pamela. How are you doing?
Pamela Gay: I am doing well. How are you doing, Fraser?
Fraser Cain: I am doing great. And I mentioned this in the preamble, but I just wanted to say this again, which is a huge congratulations to our good friend, Pamela Ian O’Neill, who just announced that he’s going to be working at NASA Jet Propulsion Lab in their media department. Ian is a terrific science journalist. One of the best in the business. And it’s a pretty good fit that he’s now working over at NASA. He was the editor for the Astronomical Society of the Pacific, Mercury. He has been a columnist for Discovery and Seeker. He did some work with us at Universe Today. And this is great. So, congratulations, Ian.
Pamela Gay: And we’re gonna take the next two weeks off. I’m gonna call it Spring Break.
Fraser Cain: Yes.
Pamela Gay: I’m not going anywhere. I’m just gonna be writing software, but you, sir, are going on a grand adventure.
Fraser Cain: Yeah. I’m going to Japan with my son. And there is – this is not work. This is literally just him – I said, “Where do you wanna go?” And he goes, “I wanna go to Japan.” And then I waited for cheap tickets to come around, and they did. And so, we’re off to Japan. Of course, we’re off to Japan when there’s a coronavirus, but we’ll take precautions. And it doesn’t look like it’s that bad there currently. So – and I can’t wait to see this place. I’ve wanted to go to Japan all my life. And to be able to do this is gonna be a lot of fun. So, I’ll definitely take pictures. Might visit a few spacey things, like the Japanese Space Agency, but this is about his trip, not my trip.
All right. Well, see, you might be surprised to hear that we’ve never done an episode of Astronomy Cast featuring Betelgeuse. Well, good news. This is that episode. So, let’s talk about the star, why is might be dimming, and what could happen if it explodes as a supernova. I – it – I had to do a search before I actually wrote up my intro. And I think we suggested this one to – for Susie to put on the calendar. And like all of this time, we’ve talked about Orion, we’ve talked about the way stars die, and we’ve obviously mentioned Betelgeuse many times as a candidate for a new supernova but had never actually spent a whole episode on this one specific star.
Well, obviously good timing on our part because it’s so interesting right now. So, what is Betelgeuse?
Pamela Gay: It is a red, supergiant star that is visible to both the Northern and Southern Hemisphere. We have no hemispheric bias in choosing this star. It has evolved off the main sequence, which means it is no longer burning hydrogen in its very core. And it probably did this only about a million years ago. And now, it is systematically burning through heavier and heavier shells of elements, deep in its, well, many, many solar mass self as it hangs out, shining bright in the northern winter and the southern summer.
Fraser Cain: And it is – it is Orion’s right shoulder. I mean, when you look at it, it looks like it’s on the left, but if you were Orion and you were facing towards us, then it would his right shoulder.
Pamela Gay: And there’s some fascinating history on its name, and I have to admit, I went down a little bit of a rabbit hole prepping for this episode. Its – its name is Arabic.
Fraser Cain: Yes.
Pamela Gay: And over the years has probably been mistranscribed, so that there are those that believe that it translates as Orion’s armpit.
Fraser Cain: Right.
Pamela Gay: And this could be caused by just dropping a little dot under one of the characters at that wrong moment in time. It probably has a much better name than Orion’s armpit. This is still up for a fair amount of discussion.
Fraser Cain: Well, actually, so one of our viewers, Rami Ahmed, who speaks Arabic, he’s saying that it is – the name comes from the Arabic [speaking Arabic], which literally means the armpit of the mighty hunter. So, that sounds better than Orion’s armpit.
Pamela Gay: It – it’s –
Fraser Cain: The armpit of the mighty hunter.
Pamela Gay: It’s true. It’s –
Fraser Cain: Yeah.
Pamela Gay: – true.
Fraser Cain: And we – we’re gonna mispronounce it. And, of course, the hilarious thing is, is how people give us such a hard time because they’re expecting that it should be Beetlejuice.
Pamela Gay: Yes.
Fraser Cain: But – and we tend to say Betelgeuse and that is – that’s a little bit of a holdover from, I think, the way they used to describe it before the movie came out.
Pamela Gay: Yeah.
Fraser Cain: And the movie sort of has shifted it to beetle, but even that isn’t correct. So, maybe we can, after the fact, maybe get Susie to get maybe Rami or someone to do the proper Arabic pronunciation in the show and – so that then can serve as the – as sort of the standby.
Pamela Gay: Yeah.
Fraser Cain: And I’ve heard a lot of people, like even Germans say, people are – say that, well, actually it’s a German word, but it’s not.
Pamela Gay: No.
Fraser Cain: It’s an Arabic.
Pamela Gay: Yes.
Fraser Cain: And it comes from – yeah. It has an Arabic root. So.
Pamela Gay: And –
Fraser Cain: Anyway.
Pamela Gay: Yeah.
Fraser Cain: So, we are gonna say Betelgeuse, and maybe even shift to Beetlejuice every now and then. Please, just bear with us.
Pamela Gay: And however you choose to pronounce it, this isn’t an object that was strictly noted and observed by people living around the Mediterranean ocean. This is an object that – its variable and its brightness as all of us can currently go out and see. And this variability appears to have first been noted by the aborigines of Australia. It is a star that crops up in the lore of society after society, but the science, the awesome sauce science is why –
Fraser Cain: Yeah.
Pamela Gay: – we’re here today. Because when you ask, which objects in the sky are most likely to go boom, this is one of the two. Eta Carinae is the other. It is strictly Southern Hemisphere, So, really Betelgeuse is the one we want so that all of us can enjoy the experience. And the problem is we don’t know when this is going to occur, but scientifically we’re pretty sure it’s not now.
Fraser Cain: Right.
Pamela Gay: But you can hope to be wrong.
Fraser Cain: Yes. Yeah. So, it’s a random event. And we’ll talk about this a little bit about what’s going on and how we might know, but – so, I just wanna talk a bit about just what stage it is, what kind of star it is compared to, say, a star like our sun. So, how does this star compare to our sun?
Pamela Gay: Radically different. Our sun is – because it is ours, it is used as the measuring stick by which we, well, measure everything else.
Fraser Cain: Right. It weighs one “the sun.”
Pamela Gay: Exactly.
Fraser Cain: Yeah, it weighs exactly one “the sun.”
Pamela Gay: Betelgeuse is estimated that when it was in the same evolutionary stage as our sun, when it was on the main sequence, burning hydrogen in its core, it’s estimated to have been just under 20 solar masses. If we had seen it during that stage, it would have been one of those bright blue O-type stars like we love to enjoy in the Orion nebula. Orion is a massive star forming region. That entire swath of the sky is rich in all the things needed to make stars, and there’s lost of young stars in that direction.
Well, Betelgeuse isn’t necessarily young; it finished burring all of that hydrogen. But because it’s so massive, as it evolved off of the main sequence, as it expanded out, it didn’t go through this massive flash that we see in smaller stars where it suddenly was like, “Boom, I’m gonna burn helium in my core.” Instead, because it was so massive, it was able to gradually transition into doing this. And as it did, it just basically migrated sideways across the color magnitude diagram, that Hertzsprung Russell diagram, ending up in the top, center of that diagram, being cool, red, and kind of unable to hold onto all of its atmosphere.
Fraser Cain: Yeah. And you say that it’s kind of – it’s not young anymore, but compared to the age of our sun –
Pamela Gay: Oh, yeah.
Fraser Cain: – it’s super young. Right? It’s a baby.
Pamela Gay: Yeah.
Fraser Cain: It’s only – or it’s – it’s already old anyway. It has a very short life.
Pamela Gay: It – it was only on the main sequence for millions of years, unlike the billions of years that our own sun will spend there. About a million years ago, it ran out of that hydrogen. And this is where we start asking, “Okay. So, when did it really settle in to being this nice, glorious supergiant that we see now, this red supergiant?” And the red supergiant is linked to, okay, we have burning going on on the inside, we’ve had a dredge-up of materials, and we think that all of these things have only been going on for tens of thousands of years.
Fraser Cain: Wow.
Pamela Gay: And when you start being able to consider that humanity has been around longer than the given the phase of a star that we’re observing, you recognize how short a period of time this is.
Fraser Cain: Yeah. And possibly even, like, agriculture has been around, right?
Pamela Gay: Yeah.
Fraser Cain: Agriculture has been around for longer possibly than Betelgeuse has been in this red giant phase. So, let’s talk a bit – like, what’s going on? Now you mentioned that it is burning. Obviously, it is not burning wood and coal –
Pamela Gay: Right.
Fraser Cain: – in the core, but what is – what is happening to the star right now and causing it to do some of the weird stuff that it does?
Pamela Gay: So, we can’t know exactly what layers it’s burning at even given moment. These stars like to hide what’s going on in their heart. What we know is while it is this red supergiant, it is going to start out burning helium in its very core with a shell of hydrogen around that. It is then going to transition. As it burns that helium into heavier elements, it’s going to transition into burning carbon, nitrogen, eventually silicon until eventually it ends up with an iron core. And it’s at this point that the star goes kaboom.
Fraser Cain: Right.
Pamela Gay: And during this process, it’s giving off massive amounts of light. What this means is it has a massive light pressure pushing outwards. And that’s what is able to support this star that is bigger in radius than Jupiter’s orbit.
Fraser Cain: Crazy.
Pamela Gay: Doesn’t reach all the way to Saturn.
Fraser Cain: Right.
Pamela Gay: But it’s trying.
Fraser Cain: Yeah, but it could gobble – it would gobble up Jupiter.
Pamela Gay: Oh, yeah.
Fraser Cain: Yeah. But it varies. And so, I mean, it is a variable star. And part of the variation comes from literally the change of the star’s size.
Pamela Gay: Yes.
Fraser Cain: So, it’s not always the size that it is right now, and it changes quickly.
Pamela Gay: And it changes all the way down to, we think, roughly asteroid belt-sized orbit. It’s hard to tell –
Fraser Cain: So like tens of millions of kilometers, possibly like a hundred million kilometers across its radius is getting bigger and smaller.
Pamela Gay: And it’s really hard to nail this down. And one of the reasons it’s so hard to nail this down is how do you define the edge of a cloud?
Fraser Cain: Right.
Pamela Gay: This star at its outermost layer – light pressure is greater than gravitational pull sometimes. And this means it’s pushing its material away. And this outflow is building clouds around it. And this is part of what makes it so hard to figure out the real age and evolutionary stage of the star, actually, because in an ideal situation we’d look at it. And sure, you can’t measure its diameter, you can’t really tell exactly how much mass it has lost, but you can get a pretty darn good estimate by measuring how much mass is around the star.
But Betelgeuse is what we call a runaway star. Due to something bad that happened in its past, it is flying through space at a fairly high velocity, and it’s losing mass as it goes. And because it’s losing mass as it goes, it’s literally leaving its mass behind.
Fraser Cain: Right. Like a cometary trail.
Pamela Gay: And so, we can’t figure out how much mass it’s lost because we don’t know where it left it.
Fraser Cain: Right. Right. Because it’s been moving for – for hundreds of thousands, millions of years. Now, let’s pretend like it will die soon. What will happen and what will remain?
Pamela Gay: Well, we don’t know all the details of what stars do before they go boom. If we did, these radical diming events that we’re gonna talk more about –
Fraser Cain: Yes. Yeah. We’ll get to the diming. Don’t worry.
Pamela Gay: – would be less exciting. What we think is the star will essentially run out of the ability to keep producing energy.
Fraser Cain: Like, it just runs out of fuel.
Pamela Gay: Yeah.
Fraser Cain: The fuel that it was using in the core.
Pamela Gay: And so, all that light pressure that was pushing out, it’s gonna stop being produced. Now, light takes a long time to exit a star. And so, it’s gonna be a gradual coming in on itself. It’s gonna accelerate and accelerate until all a sudden the infalling material, which is heating up as it goes, is going to stop just generating enough pressure to maybe hold the star together a little bit better. And it’s instead going to start hitting the pressures and the accelerating inward, driving more pressure, that is gonna cause a supernova.
Now, this object we suspect, the star we suspect, will be order of 15 solar masses when it goes boom. Order of. Again, we don’t know where it left all its mass. And that means it’s gonna leave behind most likely a neutron star.
Fraser Cain: Right.
Pamela Gay: So, we’re gonna have a classic supernova event, neutron star left behind. Think Crab Nebula, but way closer.
Fraser Cain: Right.
Pamela Gay: In my head, the way I think about this, is some day in the future when they’re teaching about the constellations and the methodology, they can upgrade the story so that Orion has a bloody shoulder from where Taurus gauged him or something.
Fraser Cain: Yeah. I mean, imagine a – and it probably would be visible with the unaided eye.
Pamela Gay: Oh, yeah.
Fraser Cain: Like, not the explosion. Like, the explosion would be absolutely visible.
Pamela Gay: Yes.
Fraser Cain: And possibly – and definitely visible in the daytime, and possibly even brighter than the full moon.
Pamela Gay: Yes.
Fraser Cain: I’ve heard estimates. So, it’ll be ridiculous. But even after it’s done and gone, the remnant will probably be bright enough to just see with your eyes just there in the sky.
Pamela Gay: Yeah.
Fraser Cain: It’ll be about the size – I mean, when you think about, say, the Crab Nebula after a thousand years-ish is – is a teeny tiny blotch in a fairly big telescope. Like, I’m imagining something that is like the size of a full moon in the sky that is just this big, red, blasted smear in the sky –
Pamela Gay: And –
Fraser Cain: – where there used to be a star.
Pamela Gay: The Crab Nebula is more than ten times further away.
Fraser Cain: Yeah. Yeah. So, ten times closer, bigger than the Crab Nebula.
Pamela Gay: That means a hundred times brighter.
Fraser Cain: Yes.
Pamela Gay: And so –
Fraser Cain: Thanks to –
Pamela Gay: – we’re gonna have something that’s a hundred times brighter. Now, it’s always going to be spread out over a larger area on the sky. So, it’s not that every arcsecond is going to be a hundred times brighter, because you have to deal with the fact that the light’s spread over a larger area but there’s more of that light getting to us. And this is a calculation I need to do. I meant to do it in time for the show, but day job got in the way. Stay tuned. This is something I’m probably gonna do for fun –
Fraser Cain: Yeah.
Pamela Gay: – on my blog at some point. But yes, we’re gonna have something bigger in the sky that we’re gonna be able to see by eyeball. It’s just a matter of how long are we gonna be able to see it before it gets so big that its light’s spread out too much.
Fraser Cain: Right. And we have examples – we do have examples of that. There’s like the Veil Nebula – the whole Cygnus supernova complex is this gigantic supernova remnant that is a huge portion of the sky. You need to take multiple images in a telescope to be able to see it. And that’s an example of one that exploded a long time ago, and we’re just seeing the wreckage just expand outward into space. So, imagine if it was a lot more compact and a lot closer and a lot brighter. So, yes. Yes, please.
Okay. So, let’s shift now to the sort of the recent excitement, the reason why Betelgeuse has come across everybody’s newsfeed and why everybody is so excited that maybe this time it’ll explode for real. So, why – so, explain the dimming. What’s going on?
Pamela Gay: Well, we don’t know exactly what’s going on, but I can tell you what we observed.
Fraser Cain: Yeah. Tell me what we observed.
Pamela Gay: So, normally Betelgeuse varies in brightness by a couple of magnitudes, worst case. And this brightening and dimming has a multiyear period density to it and it also has a hundreds-of-days period density to it. So, you have all these complex, just how bright does it get, how faint does it get at any given period, is a combination of both of these semi-regular, sometimes forget that they’re actually supposed to do something variations. This is what’s called a semi regular pulsating star. It – it’s not entire understood why these stars pulsate because really, it’s like a cloud in the parts of the star that’s undergoing these pulsations.
And so, this super diffused material is changing how big the star is, which is changing how much surface area is giving off light, which is changing the luminosity of the star. As it changes in size, it’s also changing in temperature. Fine. We’ve been observing this for hundreds of years, no big deal. But for reasons no one can yet explain but we’re trying to get all the possible observational data to eventually be able to explain it, Betelgeuse dropped down to 35 percent of its normal luminosity. Now, I’m not saying it was 35 percent off. I’m saying it was 35 percent of.
Fraser Cain: Of.
Pamela Gay: Of its normal brightness, 65 percent off.
Fraser Cain: Right. That’s a sale.
Pamela Gay: That is –
Fraser Cain: I could buy – I’ll buy two of them.
Pamela Gay: Yes, please.
Fraser Cain: And save one for a rainy day.
Pamela Gay: So, this means that folks going outside, looking at Betelgeuse who are used to seeing this amazing right – bright red star as one of their way finders in the night – and this includes me here – is going outside and suddenly is like, “Wait, where’s Orion? I can’t find it.” Because that thing you look for suddenly was the same apparent magnitude as the other shoulder.
Fraser Cain: Yeah. Yawn.
Pamela Gay: Yeah.
Fraser Cain: Yeah.
Pamela Gay: It starts masquerading as like the top two heads of Gemini or something, and you need to find the whole constellation before you can make sense of it.
Fraser Cain: Yeah. So, before the dimming, it was regularly the 11th brightest star in the sky, and right now it’s the 25th, which is – come on, Betelgeuse, you can do better than this. Right? We expect more from you. Top 25? That’s – that doesn’t even compete now. Okay. So, why do astronomers think that it’s dimming?
Pamela Gay: Well, we have three competing reasons. The two likely ones are it possibly puffed a blast of dust our direction and that dust is obscuring how we see the star. It’s distorting the shape we see, and essentially scattering light so that we see the entire star as dimmer. What we should be able to see is its brightness, as a function of color, changes in ways that are distinctive of warm dust instead of warm star. It won’t be the black body that we’re used to.
Fraser Cain: Right.
Pamela Gay: So, we’re looking to see that.
Fraser Cain: An analogy that I think about is like when you see the moon, like a full moon but there’s part clouds and you can see – and the wind is moving really quickly, you can see these clouds just moving in front of the moon like – and the moon is just changing in brightness and dimness as these clouds are moving past. And so, imagine – but the clouds – but the moon was throwing out its own clouds.
Pamela Gay: Right.
Fraser Cain: And that’s what’s – right. So, there’s one. Just clouds of dust that it threw out recently or a long time ago that happened to be obscuring our perspective, and that will clear up. So, what’s one of the other ideas they’re thinking of?
Pamela Gay: Well, the other is just like our own sun, Betelgeuse has convective cells. We talked about this last week in our episode. And these convective cells on Betelgeuse are much, much larger. And if you have the cooling flows of two different convective cells interacting in interesting ways, you can potentially end up with a big old cool spot that we’re looking at that is going, “Hi, not generating as much light. Gonna make the whole star look fainter here, people.”
Fraser Cain: Yeah.
Pamela Gay: And so, this could be an atmospheric effect where just changes in the churning of this roiling gas are giving us a cool perspective. Again, this is a thermodynamic –
Fraser Cain: Literally.
Pamela Gay: – effect. Literally.
Fraser Cain: Yeah. Literally a cool perspective, yeah. And as you said, right, we talked about that last week with the pictures of the sun, and that you see those convective cells, those bright blobs of gas. And then you see the darker regions around it. And they’re still incredibly, insanely hot. It’s just that they are darker compared to the hot parts. And so, same thing, that you’re getting less light in total just based on the way you’re seeing the star, the perspective you happen to be getting, the right combination of gigantic convective cells and then darker regions.
Pamela Gay: And just like sunspots on our own sun can be bigger in size than Earth, the sunspots on Betelgeuse, we think the biggest can be bigger than our sun.
Fraser Cain: Oh, way bigger. So, I’ve heard they are 60 percent – they can be 60 percent the size of Betelgeuse. So.
Pamela Gay: That is significantly bigger than our sun.
Fraser Cain: Yeah. Yeah. Yeah. So, like the orbit from the – from the sun to Mars – or I guess the – from the sun to Jupiter. Right? So, imagine a sunspot that is hundreds of millions of kilometers across.
Pamela Gay: Yeah. That’s big.
Fraser Cain: Yeah. And again, I doublechecked that, and it’s not 60 percent the size of the sun. It’s 60 percent the size of that sun, Betelgeuse. Okay. So, that’s two reasons. Right? You’ve got dust, you’ve got just like a happenstance of convective cells. And what? The third idea is just that it is in one of these expanding and contracting phases.
Pamela Gay: And the added step of that is that it’s in one of the contracting phases. And as its surface area gets smaller, the amount of light we get will last. And maybe we just completely screwed up how old the star is. Maybe the star evolved off the main sequence much longer ago than we thought. Maybe we’ve misjudged when it had its first dredge-up and we don’t fully understand the chemistry in the outskirts of a star. And maybe it actually is gonna go boom, but very, very few people – it’s basically the “We’re hoping we’re completely wrong because we wanna see a supernova.”
Fraser Cain: Right. Yeah.
Pamela Gay: Can we please be wrong?
Fraser Cain: And so, let’s talk about – I mean, obviously we know that it could explode some point within the next hundred thousand years or so, maybe the next million years or so. We could be the ones to witness it.
Pamela Gay: Yes.
Fraser Cain: But there’s no reason to believe that this is – this is the – this is that time.
Pamela Gay: No. Betelgeuse doesn’t care what you or I want.
Fraser Cain: Right.
Pamela Gay: It just follows the rules of physics.
Fraser Cain: So, why does dimming not tell us that it’s about to turn into a supernova?
Pamela Gay: Because there’s these other effects that can make it dim as well.
Fraser Cain: Right.
Pamela Gay: And –
Fraser Cain: And there was an interesting post from Ethan Siegel. He was sort of talking about this. And the gist is just like it just takes time for things in the core of the star to reach the surface, thousands of years. And so, whatever we’re seeing in the core, whatever is happening in the core, we won’t know about it for thousands of years. And not just like the time it takes for the light to get from – but the time is takes for that radiation to actually make it through the material in the star. So, whatever features you’re seeing on the surface of the star right now, aren’t necessarily what’s happening inside the star.
Pamela Gay: And this is where looking at its long-term behavior matters so much. It was talked about by Ed Gehring back in December that this is an unusual low, but if it’s just something having to do with its normal periodicity it should start to rebrighten right about now.
Fraser Cain: Yep.
Pamela Gay: And –
Fraser Cain: It kind of looks like it has flatlined, right?
Pamela Gay: It doesn’t just look like it’s flatlined, but for the past two days, multiple observers, observations combined, are showing that it just might be starting to rebrighten.
Fraser Cain: Right.
Pamela Gay: So, instead of being that low of 35 percent its normal brightness, it’s now crept its way up to being 39 percent of its normal brightness.
Fraser Cain: Right.
Pamela Gay: And so, maybe it’s starting to come back out, in which case the question becomes what is the slope? And that starts to tell us what might be causing this effect. We’re catching a star in the process of dying. Human society might actually even last long enough for us to document the entire thing. I mean, who knows.
Fraser Cain: Yeah.
Pamela Gay: Maybe you’ll still be around in 100,000 years in your –
Fraser Cain: In my – yeah, in my robot body.
Pamela Gay: – one cell – yeah, yeah. But this is the first time we’ve gotten to document this.
Fraser Cain: Yeah.
Pamela Gay: This is a star six hundred lightyears away. It’s not that far away in the grand scheme of things. It’s big enough we can see it as multiple pixels on a detector. We can see its sunspots, we can see right now, using the very large telescope and its sphere instrument that the shape has changed. This is not the spherical star we saw a year ago. This is this weird, distorted something that – it may not be physically distorted, but the places where the light is coming out are –
Fraser Cain: Yeah, yeah.
Pamela Gay: – distorted.
Fraser Cain: And I think that’s important. Yeah. So, I had – it looked – when you look at the pictures, you can see this sort of really bright blob at the top and this darker region down – it looks like the star is blobbing out, but it’s almost certainly that it’s just a region that is bright and shining and a region that is less shiny.
Pamela Gay: And –
Fraser Cain: Possibly with a cloud, as I mentioned, passing in front of it. Or –
Pamela Gay: And the way –
Fraser Cain: But it’s not actually.
Pamela Gay: – to think of this is a super dirty lampshade outside. I have some outdoor lampshades that dirt and grime and stuff have all gathered in the bottom of the lightshade. And so, when you look at the light, it’s not this pretty sphere of light; it’s this modeled grossness reminding me I need to clean the lampshades.
Fraser Cain: Right.
Pamela Gay: Well, the dust and grime around Betelgeuse, the darkness from whatever convective cells may be merging, all of these different things can add up to what appears to be a non-spherical star that’s just spherical, but doesn’t have a blob of dead bugs like my lamp.
Fraser Cain: Right.
Pamela Gay: But it’s got a blob of dust.
Fraser Cain: Right. So, I think as we bring this episode home, it’s absolutely fascinating star, wonderful that we have such an incredible red, supergiant so close to us. Probably not gonna explode in our lifetime, but –
Pamela Gay: But I want it to.
Fraser Cain: Of course. We all do. Come on. And anyone who’s worried about the Betelgeuseians, they’ve only known suffering for the short – few short millions of years this star has been around.
Pamela Gay: It’s true.
Fraser Cain: That the explosion of this star would be really just icing on the cake of just a few short million years. Like you can just imagine, right? Your star –
Pamela Gay: Our solar system hadn’t even finished the great heavy bombardment at the point in its history that is the same number of years as the Betelgeuse system has been around. It’s a baby solar system.
Fraser Cain: Yeah. Yeah. So, like, think about how long planets take to form. It’s already died in that process. Not to mention, it is pumping out radiation at obnoxiously high levels. Not to mention, it changes in size from –
Pamela Gay: Bigger than Jupiter’s orbit.
Fraser Cain: – from the size of the asteroid belt to the size of Jupiter. You try to live near a star that’s changing – like, there is nothing habitable around Betelgeuse. When that star goes –
Pamela Gay: We can see it.
Fraser Cain: – we’ll be able to see it. Well, but we’ll keep you posted if anything does happen. Pamela, do you have any names for us this week?
Pamela Gay: I do. I just wanna once again, thank all of you out there who support us month after month. And we’re here thanks to you. Susie is able to do all the heavy lifting around here, and we can pay her because of your patronage. And we couldn’t do this show without having her there to do all the heavy lifting. So, I wanna thank those people who really made this possible.
And this week, I’m gonna thank Michelle Cullen,Neuterdude, William Lauer, Eric Farenger, Ryan James, Shannon Humber, Kristin Brooks, Glenn McDavid, Dan Litman, Kseniya Panfilenko, Dean, Matthias Heyden, Benjamin Davies, Russell Peto, Martin Dawson, Cemanski,Dana Nourie, Bart Flaherty, Father Prax, Andrew Stephenson, Kenneth Ryan, Dean McDaniel, Donald E.Mundis, and Anitusar.
Fraser Cain: Awesome. Thank you, everyone, for your continued support of what we do. You support us directly so that you can get your space news from us as opposed to relying on some traditional, old school media channel. I mean, I’m not saying it’s aliens.
Pamela Gay: It’s not aliens.
Fraser Cain: It’s not aliens. All right. Thanks, Pamela. We’ll see you in several weeks. So, stay tuned when the next episode comes out when I’m back from Japan. Thanks, everybody.
Pamela Gay: Bye-bye.
Female Speaker: Thank you for listening to Astronomy Cast, a nonprofit resource provided by the Planetary Science Institute, Fraser Cain, and Pamela Pamela Gay. You can find shell notes and transcripts for every episode at Astronomy Cast. You can e-mail us at info@astronomycast.com. Tweet us @astronomycast, like us on Facebook, and watch us on YouTube. We record our show live on YouTube every Friday at 3:00 p.m. Eastern, 12:00 p.m. Pacific, or 1900 UTC. Our intro music was provided by David Joseph Wesley, the outro music is by Travis Sorel, and the show was edited by Susie Murph.
[End of Audio]
Duration: 36 minutes
Download MP3| Download Raw Show with Q&A| Show Notes | Jump to Transcript or Download
A brand new telescope has completed on Maui’s Haleakala, and it has just one job: to watch the Sun in unprecedented detail. It’s called the Daniel K. Inouye telescope, and the engineering involved to get this telescope operational are matched by the incredible resolution of its first images.
Download MP3| Download Raw Show with Q&A| Show Notes | Jump to Transcript or Download
Show Notes * New Solar Telescope Produces Most Detailed Images of the Sun Ever [Video] (SciTechDaily) * The Sun (Wikipedia) * Our Sun is a G-type main-sequence star (Wikipedia) * Daniel K. Inouye Solar Telescope (Wikipedia) * Daniel K. Inouye Solar Telescope (NSO) * Welcome to the DKIST (NSO) * How the world’s largest solar telescope rose on Maui while nearby protests derailed a larger scope (Science) * World’s most powerful solar telescope is up and running (Nature)
Transcript Transcriptions provided by GMR Transcription Services
Fraser: Astronomy Cast Episode 559 – The Surface of the Sun. Welcome to Astronomy Cast, a weekly facts-based journey through the cosmos where we hope you understand not only what we know, but how we know what we know. I’m Fraser Cain, publisher of Universe Today. With me as always is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute and the Director of CosmoQuest. Hey Pamela, how you doing?
Pamela: I – I’m doing well and I’m so pleased to say that since our last episode when we said that we’re looking for help with CosmoQuest’s Open Source Project, I’ve had a number of Astronomy Cast people show-up on CosmoQuest’s Discord and we’re pulling together a great group of humans. So, thank you all the humans out there interested in helping us with CosmoQuest.
Fraser: And, let’s say a person didn’t hear that first call for – for help and may still want to throw some code into the, I don’t know my analogy is falling apart here.
Pamela: GitHub, falling into the GitHub, yeah.
Fraser: Into the GitHub, yeah. Throw some code at the GitHub. How can people get involved?
Pamela: The – the best thing that you can do is go over to cosmoquest.org, click on the Discord link, and say, “Hi” in the volunteers reporting for duty channel. And, we will add you to our Coder’s group, add you to the GitHub repo, and off we shall fly, open-source away.
Fraser: That sounds great. Alright, so a brand new telescope has been completed on Maui’s Haleakala. And, it has just one job, to watch the Sun in unprecedented detail. It’s called the Daniel K. Inouye Telescope. And, the engineering involved to get this instrument operational are matched by the incredible resolution of its first images. And, I think we need to apologize in advance to everyone who is listening to this episode conveniently as a Podcast because I’m probably gonna be showing some pictures. We are gonna be talking about one of the most incredible images of the Sun that has ever been taken.
And so, I think the hope here is that the listeners are already familiar with this image and now they’re waiting for their favorite astronomy explainers to follow-up and give them some – some context to what it is. But, if you don’t, I’m sure we’ll have a link in the Show Notes. Search for Sun surface picture on Google and you will have this incredible picture. If you get hungry for Caramel Corn, you are – you are looking at the right image.
Pamela: And – and, if you go find it on YouTube, you’re just gonna want to stare at the Sun’s surface, with this telescope not with your eyeballs, kinda forever.
Fraser: Yeah, yeah. It’s so beautiful. That’s a – that’s a Bug’s Life reference. Okay, so let’s talk about this picture.
Pamela: Okay.
Fraser: Let’s talk about this telescope. Where should we start?
Pamela: Let’s start with the telescope.
Fraser: Okay.
Pamela: Well, it’s hard to talk about an image when you know nothing about the telescope. One of the things that we’ve brought up over and over and over on this show is you can get higher resolution images by using telescopes with a larger diameter. You can do this with interferometry. You can do this with larger collecting areas. And today, we’ve never gone too gung-ho collecting light from the surface of the Sun because the Sun is a giant, hot, boiling ball of plasma and its light can melt things.
Fraser: Yeah, and then when you concentrate it with a mirror as we have seen with what you do when you have a magnifying glass –
Pamela: Yeah.
Fraser: You – you turn the sunlight into a laser beam.
Pamela: I – I have inadvertently started fires twice with telescopes, looking at the Sun.
Fraser: Yeah, I have merely destroyed a telescope. Yeah.
Pamela: Oh, I – I’ve been very good about not destroying telescopes; it’s just the things around them I keep setting on fire.
Fraser: Yes. I’m not sure which one is worse. I’m gonna say that what you’ve done is worse than what I’ve done. I’ve merely destroyed a $200.00 telescope; you’ve tried to light a house on fire.
Pamela: A piece of paper and some carpeting, but.
Fraser: Yeah, that’s funny. Right, so trying to magnify the light from the Sun is madness, and yet –
Pamela: And yet –
Fraser: In order to see detailed images of the surface of the Sun, you wanna magnify the image. How can this be done? What wizardry?
Pamela: Very – wizardry is the correct answer. So, every single aspect of this telescope is designed to make this system as safe as possible and to prevent any excess heat. This means that the dome has a unique design. Where instead of having the normal roll-up slit that leaves this big stripe of opening into the dome, they have a circular annulus that –
Fraser: Right.
Pamela: Opens up that is matched to only let in enough sunlight to illuminate the entirety of the 4-meter mirror that’s on this telescope. So, they start by restricting how much light gets into the dome. Now –
Fraser: Yep. So, they – they – and, to just – before you continue on a four, I think, it’s like a what? A 4.2-meter mirror –
Pamela: Yeah.
Fraser: That’s – it’s – that’s a big mirror. I mean it’s –
Pamela: And, it’s super thin, it’s 75-millimeters thick.
Fraser: Right.
Pamela: So, this is a system that they can do adaptive optics with and –
Fraser: Yeah.
Pamela: It’s also thin so that it doesn’t overheat.
Fraser: Right.
Pamela: This is one of the amazing mirrors that came out of the Mirror Lab in Arizona.
Fraser: Right. And so, it’s got these actuators underneath the surface of this, of the primary mirror that allow it to – to make minor distortions and – and try to compensate for the atmosphere that’s above it. So, you’ve got this – this enormous amount of light going into this – this 4-meter, 4.2-meter hole on the side of the – this observatory, bouncing off of this primary – getting focused and –
Pamela: Now, now I do have to step back and say that while the mirror is more than 4-meters in size, they’re only utilizing 4-meters of the mirror.
Fraser: Uh-huh.
Pamela: This – this is, a design where they’re not going all the way out to the edge when they use it.
Fraser: Yeah.
Pamela: And, they also are focusing it in a kinda crazy way which is also part of why they’re not using the entirety of the mirror. They didn’t wanna have to put anything in the path of the sunlight.
Fraser: Right.
Pamela: So, they have the light coming in through that exactly sized hole in the dome of the telescope. The sunlight goes through that hole, hits the mirror which is tilted and shaped ever so slightly to direct the light out of the side of – of the incoming light. So, the light comes in, bounces sideways –
Fraser: Right.
Pamela: Gets focused onto a secondary liquid-cooled metal donut of a system.
Fraser: Yes. Yeah, they call this the heat-stop.
Pamela: And, this incredible system eliminates 95% of the heat.
Fraser: Right.
Pamela: This –this prevents them from melting anything further down.
Fraser: Right. And, I think that the thing that’s really important, so a couple things there, as you were saying, right? With a traditional solar telescope you put your, the block, whatever you’re gonna use to decrease the brightness of the Sun, you put that at – in front of the main hole on the telescope.
Pamela: Yes.
Fraser: So, if you’ve got a Newtonian Telescope, you put it in front of the entire, before the light can even get inside your telescope, you’ve already shaded it.
Pamela: They’re not doing that.
Fraser: And, and – and they’re not doing that. They’re – they’re waiting. And so – and so, – the – and the reason, if I understand is that they don’t wanna have even slight problems with whatever filter they would have to put in front of it. That would decrease the quality of the image.
Pamela: So, their goal is to remove anything that might create contrast issues, remove anything that might create optical aberrations, remove basically, anything extra that they don’t absolutely, have to have. The light comes in; they have 95% of the light from all 44-meters of the telescope going up to this donut. So, they’re keeping the resolution and throwing out unnecessary light so they can still do all the science they want, and get maximal-resolution out of their detector.
Fraser: Right.
Pamela: Now, at this point, it starts to act more like a normal telescope. They’re shooting the light down to what’s called a coudé focus. This is where you have some sort of a split that takes the light and moves it from that room that your telescope is living in and generally shoots it to the basement somehow.
Fraser: Right.
Pamela: Lot’s of telescopes do this in different ways. The 107-inch telescope at McDonald Observatory, which I’ve used the coudé spectroscope on, it shoots it through the – the pier of the telescope, down through the floor, and into a different room using mirrors. The Hobberly Eber – Hobby-Eberly Telescope, it uses fiber optics to do this. Lots of telescopes nowadays are accomplishing this with fiber optics. They pickoff the light, move it through the cables, get it into their big basement room. Now, the reason you’re using this big basement room is so that you can have massive instruments to spread the light out to create spectra, do all sorts of amazing stuff.
And, normally you have some sort of rotational system to keep things fairly aligned, but you’re looking at stars. You’re not looking for too long and you’re not worried about rotation too much. They’re looking at the Sun, the entire day.
Fraser: All day long. Yeah.
Pamela: Yeah. And so, they do what I consider to be one of the most crazy, awesome things I have ever seen done with a coudé room. They’re rotating the whole darn room.
Fraser: The whole room just turns –
Pamela: Yes, yes.
Fraser: To keep the instruments it – aligned with the – with the telescope and everything that’s bouncing around.
Pamela: This is a 150-ton platform of instrument –
Fraser: Yep.
Pamela: That they are precisely rotating as they track the Sun. So, their tracking isn’t just moving a 4-meter telescope. Their tracking isn’t just moving very precisely a dome. And, domes normally don’t have to move – move precisely. They have to track the dome precisely, track the telescope precisely, and track the 150-ton coudé laboratory precisely. This is remarkable engineering. I – I can’t imagine what the construction company they went to originally thought when they were asked, “Can you make this entire room track the Sun?” Yes, they could. But, probably not anything anyone expected they’d be doing when they got their mechanical engineering degrees. It’s a feat of engineering that –
Fraser: Yeah, it really is. One of the other feats of engineering is just temperature control.
Pamela: Yes.
Fraser: I mean, again, you’re bringing in I think it’s like 12 kilowatts of energy nonstop, continuously just bringing in enormous amounts of energy into this enclosed space. And, you have to get rid of it.
Pamela: Yeah. And – and, they do this through a variety of ways. They have, first of all, extra gaps, in this case, rooms between the dome floor. And then, when you get down to the instrumentation, having extra rooms, well it’s sort of like having storm windows in your house. Those air gaps provide a place where heat gets dumped and then doesn’t get transferred. And then, they are just coolant-ing everything. That donut, I’m just gonna be in awe for a while.
Fraser: Yeah, yeah. So, they – if you look at the outside of the – of the actual shutter, of the outside of the dome, they’ve got these – these flappy shutters –
Pamela: Louvers.
Fraser: Yeah, that are all across the outside of it. And so, they can do a lot of really, sort of high and quick, quick – very – quick response temperature control. They make ice in the observatory at night when it’s cooler on the top of this mountain and then they pump it through. They use this as a way to – to run coolant through the entire system. There’s like seven kilometers of coolant piping throughout this entire instrument. So again, and as you said, they have all this air gapping inside that – that they can then also use to – to try to – to maintain the tee.
And so, the goal is just to, that every single part of this entire telescope, from the mirror to the instruments, all the way down to the ground level, the whole thing is precisely the same temperature all the time.
Pamela: And – and, that is really the key. And, this is a problem that we’ve been trying to solve with telescopes for a while now. Once our telescopes got good enough, we realized air is the enemy, because if you have temperature variations in the air, each of those temperature variations will bend the light. Air can act like a lens, its super annoying. Now, with a regular everyday telescope, you open the dome, you turn on some fans, you make sure all the doors are open, and you’re good enough. But, as we’ve started building bigger and bigger telescopes, we’ve had to start figuring out how to add all of these basically, Venetian blind systems that open up and circulate all the air.
So, all day long inside these nighttime telescopes, you run air conditioning to try and keep the room at the temperature you expect the nighttime to be. Well, here they’re flipping that on its head and they’re trying to keep everything the temperature it’s going to be during the day and not have any greenhouse effect going on. So, just like our – our cars will heat up in the sunlight, domes will heat up in the sunlight.
Fraser: Yeah.
Pamela: And, that would be death to the system’s accuracy.
Fraser: And, you’re bringing in all that heat.
Pamela: And, you’re bringing in heat.
Fraser: Yeah.
Pamela: So, essentially they’re bringing in heat and they have to constantly prevent that heat from heating up the air. And, it’s not easy and they have figured it out.
Fraser: Yeah.
Pamela: And, this is where I think we should start talking about these amazing images.
Fraser: Let’s do that. And so, again if you – if – if you need to pause the Podcast, go get yourself in front of a browser, and take a look at the pictures that, that this – this – this incredible telescope has – has taken. And so, now assuming that you have done this or you’re kinda familiar or you’re just gonna sort of follow along with us. Tell us, and I’m gonna show the picture for the people who are watching this as the Livestream, but tell us kinda what we’re looking at.
Pamela: So, the – the image that the – this telescope produced is a series of hot cells that are yellowy in the center, fade-out, and then are surrounded by inky black darkness. Now, the crazy thing is that inky black darkness is still super bright. What – what we’re seeing is slight temperature variations in the surface of the Sun where convective cells of hot gas are rising-up. And then, through the center, they’re rising up and then cascading down as they give off their heat to outer space.
And, because luminosity causes temperature to the fourth power, the very small temperature variations from the center of these convective cells out to the cool edges of these convective cells, well they have amazing differences in luminosity. That, because of the limiting contrast of what we can do with images and eyeballs, we perceive as dark out – outlines around bright cells.
Fraser: And – and – and so, sorry, so like the bright parts that we’re seeing.
Pamela: Uh-huh.
Fraser: Those are the hottest parts, the parts where the Sun is, actually blobbing out its convective material from the interior. And then, the darker regions are still insanely hot.
Pamela: Yes.
Fraser: Just less hot than the actual bright surface.
Pamela: And – and, what makes these particular images so remarkable is each of these convective cells is roughly the size of France or Texas, which are remarkably about the same size, but Texas is bigger. These convective cells on the Sun are the size of France or Texas. And, we can make them out, not just as a few pixels across but as gazillion, not literally gazillions –
Fraser: Yeah.
Pamela: But, as a lot of pixels across, because this instrument can resolve features that are just 12 miles or 20 miles in – 12 miles or 20 kilometers in size.
Fraser: Yeah, yeah. So, the little – if you zoom in on the image and you can see individual pixels, these are on the order of 12 – as you say, like 20 kilometers across. And, when you think about the fact that we’re seeing these images from 150 million kilometers away, it’s just an incredible feat of – of engineering in astronomy to be able to do this.
Pamela: And, the entire field of view for this telescope is – is measured in arcseconds. This is an extremely high-resolution system. We’re never gonna get Full-disk of the Sun. Heck, there may be Sunspots that come up that are bigger than this telescope can see.
Fraser: Yeah.
Pamela: But, with this kind of resolution, even now in its engineering phase, we’re seeing things that when you try and look up information on them, current publications say, “Can’t be resolved. Not well understood. Bright things.” Faculae are what I am thinking of here, we know that there are magnetic effects that occur in those dark boundaries between individual convecgive – convective cells and these bright magnetic effects aren’t well understood. And, this may be how we finally are able to understand them. This telescope is still in the process of being commissioned. We’re talking about it now because we’re getting amazing images off of it.
And, the time is right to say, “Photosphere here we come.” The top 50 miles of the surface of the Sun is about to be ours to understand in detail.
Fraser: So then, what is the point? Now obviously, it’s incredible to see these high-resolution images of the Sun. But, what is it good for? How does this make my life better?
Pamela: Well, it’s hopefully gonna help us better understand solar weather, better be able to make predictions of what’s going on. The top layer of the Sun, while generally kind of ignored because it’s not as striking as the – the higher up layers, this – this photospheric layer, it varies from hot spot to cold spot between about 4,500 degrees and 6,000 degrees Kelvin, that’s 4,200 to 5,700 Celsius. And, the effects that occur at this level, lead into bigger and bigger effects as you go up in the Sun’s atmosphere. The faculae that we see as bright nothings at the surface of the Sun, at the photosphere, end up growing into bigger and bigger things called flages as you get higher up in the atmosphere.
These can end up forming coronal loops that in the outermost layer of the Sun, these are the big magnetic loops that we see that when they let loose can blast particles our direction, that take out communication satellites.
Fraser: Right. And, – and that’s like if you want the real practical advantage for observing the Sun at this level of detail, advance-warning of a solar storm that’s going to cause a serious disruption to our modern interconnected human society is – is the benefit that you enjoy, is some advance-warning. Like, right now, what do we get? Like two hours of notice that there’s a significant solar storm inbound because –
Pamela: Yeah.
Fraser: We’re starting to detect the first particles smashing into the earth.
Pamela: Hitting Solar Dynamic Orbiter. Well, we also, so this is where Solar Dynamic Orbiter has so far played such an important role. This little spacecraft that can is sitting out balanced between the gravity of the Earth and the Sun, close enough to the Sun that particles hit it. And, thanks to the speed of light being so much faster than the speed of particles, it can go, “Earth, there’s stuff coming.”
Fraser: Yeah.
Pamela: And, we can safety things. We can send astronauts for cover if we need to.
Fraser: Yeah.
Pamela: And, that early warning is amazing. Now, what would be even better is – is, predictive models. This is the – the difference between looking at radar right now and seeing a tornado on radar heading towards your house and having satellite images that allow you to predict a potentially dangerous storm is brewing.
Fraser: Right, yeah.
Pamela: Right now we use spacecraft to predict weather on Earth. Well now, we’re gonna use Earth-based telescopes to predict weather on the Sun more effectively than we can do with spacecraft. And, I love this inner play of how we need all these different kinds of observations to make sense of what we’re learning.
Fraser: And, the hope here is that we’ll get of couple days of notice. That astronomers will see these features on the Sun, see them brewing, see a – a burp forming on the Sun.
Pamela: Yes.
Fraser: That’s going – and – and understand how all of these – these pieces are connected, right? When you look at that picture of the – of the roiling, bubbling surface of the Sun, how do you know that any, one of those areas is about to cause a – a coronal mass ejection? It’s just, you just don’t. And so, but being able to sort of trackback and use as you say these predictive models of the Sun, we’ll get to this point where suddenly now astronomers can look at all these regions and go, “Okay.”
Pamela: Yeah.
Fraser: “It – you wouldn’t have known before but now we do know that this region right here that is slowly rotating towards the Earth, like the Death Star, is about to let off a blast that could cause us a problem. And so, unplug the electronics that you care about.”
Pamela: And, what’s more, as we’re looking to start putting human beings in space outside of the Earth’s magnetic field, Moon, Mars, wherever. We may only have a small volume of space that is adequately protected from radiation that they can stay healthy if their spacecraft gets hit by a burst of energy from the Sun. Having this kind of predictive model will tell them perhaps ahead of time, “Hey, maybe you wanna come back to the Earth a few days earlier if you’re on the Moon. Hey, get ready to go into hiding as you’re on your way – way to Mars.” We are lucky to have our magnetic fields. And so, we first of all need to be afraid, just like you say of, of another, what we call a Carrington Event, a massive burst of energy from the Sun capable of doing bad things to our power grid, to our satellites, to our astronauts, and lower Earth orbit. We also need to be able to predict what’s gonna happen at the Moon, at Mars. All of these things are necessary to keep the science flowing and the humans alive so.
Fraser: Well, and I wanna know when I should go and see auroras.
Pamela: Well, yeah. That’s true too.
Fraser: But, right now all we get is we get a couple hours of warning that there’s auroral activity. Not even, we get there’s auroral activity right now. Well, it’s too late for me to book my trip to Iceland. But, if I could get two days’ notice that’s there’s gonna a big storm coming, then I can book my trip to Iceland and go and enjoy powerful auroras.
Pamela: I was gonna say road trip to Canada, but sure.
Fraser: Sure, that place, yeah. It’s a big country. It’s easier to fly to Iceland than to road trip in Canada.
Pamela: That’s probably true.
Fraser: And, it’s much better equipped than, Northern Canada is a – is a hard place to be. While, I gotta say, being in Iceland is a – is a, quite the luxurious experience. I quite liked it, even in the wintertime, right? Wintertime in Iceland is delightful compared to wintertime in Canada.
Pamela: Still on the bucket list.
Fraser: Yeah, yeah. So, I mean this – all we’ve seen right now is the first light images. Chances are you’re gonna bored of because every image is – kinda look like this, just different flavors of variations on roiling plasma on the surface of the Sun. But, we are gonna see Sunspots –
Pamela: Yes.
Fraser: And other interesting features over time as well. So – so, stay tuned.
Pamela: Now, this instrument – this instrument won’t be fully built until this summer. They’re aiming for –
Fraser: Yeah.
Pamela: Having all the spectrographs, all the polarimeters, all of the devices that will allow us to study even more effectively, the – the outer layers, the temperature, the magnetic fields. This summer, it’s coming. We just have first light.
Fraser: Yeah, yeah. So, more instruments coming. So, stay tuned. Right on, I’m – I’m super excited about this and I did a video on my YouTube channel as well. So, if people wanna follow even more information, they can follow that there. Pamela, do you have some names for us this week?
Pamela: I – I do. As always, we are brought to you by you. We are so grateful to all of our Patreons.
Fraser: That’s very recursive.
Pamela: Well, it’s true, it’s true.
Fraser: Yep.
Pamela: We – we are so grateful to all of our patrons over on patreon.com/astronomycast. If you can support us, please do. If you can’t, we totally get it. Just leave us your review somewhere. Help people find our show, we’re good. So, I really wanna thank this week Jordan Young, Burry Gowen, Frada Tombow, Ramji Enamuthu, Andrew Palestra, David Truog, Brian Cagle, The Giant Nothing, Laura Kettleson, Robert Palsma, Corey Davolli, Paul Garman, Les Howard, Joe Cunningham, Emily Patterson, A Blip in the Universe, Infinitesimal Ripple in Space-Time, and Ed.
Fraser: Awesome. Thank you everybody, and – and as always, Pamela thank you for bringing the knowledge. And, we will see everyone next week.
Pamela: Sounds great. See you all later.
Fraser: Bye-bye.
[No dictation] [00:28:48 – 00:29:18]
Speaker 3: Thank you for listening to Astronomy Cast, a nonprofit resource provided by the Planetary Science Institute, Fraser Cain, and Dr. Pamela Gay. You can find show notes and transcripts for every episode at Astronomy Cast. You can email us at info@astronomycast.com, tweet us @astronomycast, like us on Facebook, and watch us on YouTube. We record our show live every Friday at 3:00 p.m. Eastern, 12:00 p.m. Pacific, or 1900 UTC. Our intro music was provided by David Joseph Wesley, the outro music is by Travis Serle, and the show was edited by Susie Murph.
[End of Audio]
Duration: 30 minutes
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We’ve been following this story for more than a decade, so it’s great to finally have an answer to the question, why was supernova 2006gy so insanely bright? Astronomers originally thought it was an example of a supermassive star exploding, but new evidence provides an even more fascinating answer.
Download MP3| Download Raw Show with Q&A| Show Notes | Jump to Transcript or Download
Show Notes
* SN 2006gy (Wikipedia)
* The Brightest Supernova Ever (NASA Science, 2020)
* Weird Object: SN 2006gy (Astronomy.com, 2015)
* SN 2006gy: NASA’s Chandra Sees Brightest Supernova Ever (Chandra, 2018)
* A type Ia supernova at the heart of superluminous transient SN 2006gy (Science, 2020)
* Supernova 2006gy (Solstation.com)
* Astronomers Astonished by ‘Monstrous’ Star Explosion (Space.com, 2007)
* SN 2006gy: Discovery of the most luminous supernova ever recorded, powered by the death of an extremely massive star like Eta Carinae (Cornell via ArXiv, 2007)
* Quark nova imprint in the extreme supernova explosion SN 2006gy
(Cornell via ArXiv, 2012)
Transcript Transcriptions provided by GMR Transcription Services
Fraser: Astronomy Cast, Episode 558. Finally explaining Supernova 2006gy.
Welcome to Astronomy Cast, where we take a fact-based journey through the cosmos, where we help you understand not only what we know, but how we know what we know. I’m Fraser Cain, publisher of Universe Today. With me, as always, Doctor Pamela Gay, a senior scientist for the Planetary Science Institute and the director of CosmoQuest.
Hey Pamela, how you doing?
Pamela: I’m doing well. How are you doing?
Fraser: Doing very well as well. Well, as well. Anything new happening in Your-verse, the CosmoQuest-verse?
Pamela: It won’t stop snowing.
Fraser: Yeah, we got a few extra snowfalls too.
Pamela: So, we are plugging away every winter’s day on our new code set. One of you out there, you know who you are, actually came over and joined us on Discord to help us out with the coding and that made me super excited. So, if any of you want to donate some time and join our opensource project, we’re doing a complete rebuild and you are all welcomed. And I get super happy if you say you understand JavaScript.
Fraser: Complete rebuilds are always fun. And by that, I mean never.
We’ve been following this story for more than a decade, so it’s great to finally have an answer to the question, why was Supernova 2006gy so insanely bright? Astronomers originally thought it was an example of a super massive star exploding, but new evidence provides an even more fascinating answer.
All right, Pamela, do you remember where you were when Supernova 2006gy exploded? It was actually before our time on Astronomy Cast, wasn’t it?
Pamela: Yeah, so I would have just moved here to Illinois. I would have been a baby professor. We would have just started the show. This was an end of the year supernova. And so, I don’t know exactly where I was, but it wasn’t too far from here.
Fraser: I don’t remember the story. You know I had to go and look in the archives at the time when we reported on it and then all the various updates that we reported on this story. And it’s one of those things, though, where when you do kind of look back at the story with all of the knowledge that we now have, you can see the whole thing unfolding bit by bit.
And so back in 2006, as you say, at the end of the year, astronomers saw a supernova that was unlike anything that they had ever seen. So, what was wrong with it?
Pamela: Well, not necessarily wrong, but the thing that was initially fascinating about it is it was just way brighter than we had previously seen. Once you corrected for distance, it had the highest luminosity up until that date. So, with massive amounts of energy coming out of it and with a crazy light curve, it was initially assumed that this was what’s called a Type II supernova. The explosion of a massive star that’s going to leave behind a neutron star or black hole.
But different kind of supernova are supposed to increase and decrease in brightness in very set ways. And while this started out looking like a Type II supernova, it didn’t stay looking as Type II supernova.
Fraser: So, let’s talk – I mean we’ve done whole episodes on all the different flavors, but let’s go back and give people the quick overview of the different kinds of supernova that you can expect to see out there.
Pamela: So, broad physics case, you have supernova that are single stars that are generally massive and when they run out of fissionable materials in their core that can generate new energy, they stop producing light pressure that supports the outer layers of the star and they collapse under gravity. And all of that collapsing material triggers a new round of thermonuclear reactions. The star now explodes outwards as a supernova. So, that’s one model of behavior.
Now, the other model of behavior is you have something like a white dwarf that is made out of, what we call, degenerate matter. A white dwarf is an object roughly the size of the earth that has the mass of the sun. And when you cram all of that mass into so small a volume, you end up with the electrons having to arrange themselves in a very specific way to avoid breaking the Pauli Exclusion Principle.
So, all of the electrons are like, you, okay, you be in this level, you be in this level, we’ll spin in these particular ways. And this electron degenerate gas is as tight a gas as you can form out of the electrons. And if you compress it too far, the electrons can no longer support each other. Pauli Exclusion Principle breaks; those electrons and the protons that are associated with end up merging and forming neutrons, everything goes badly. There’s a lot of energy released.
And this is the other way you can get a supernova is by piling too much mass on one of these electron degenerate gas white dwarf stars defying the Pauli Exclusion Principle and exploding that white dwarf. That’s a Type Ia supernova. Now, in general, because Type Ia’s all detonate at the same amount of mass, they’re supposed to be the same amount of light.
Now, the names for those massive stars that are exploding are all over the map. There’s Type II, there’s Type 1c, there’s all these different letters added on, but they’re all massive stars.
Fraser: So, okay, so just to sort of follow the mystery. Astronomers saw what was inherently the brightest supernova they have ever seen?
Pamela: Yes.
Fraser: But so, then it couldn’t have been a white dwarf because they’re not that bright?
Pamela: Exactly. At least that’s what was initially thought.
Fraser: Right.
Pamela: So, you have – their initial thinking, and I’m going over this so I can make sense of all of this later because no physics is harmed in this episode. So, you have a white dwarf worth of energy tied up in the mass. And that amount of energy when it goes boom always releases the same amount of energy.
Fraser: Right, right. And the sort of example, right, I mean, essentially, it’s like one big diamond the size of the earth. It is this carbon, as you say, this carbon lattice. And the moment it crosses over this line where the thing collapses inward, the whole thing just turns into carbon burning and it’s just gone.
Pamela: Yeah.
Fraser: Like, kaboom, and it’s gone. Because the whole thing – suddenly a lifetime’s worth of fusion happens in an instant. Every atom in the entire star proceeds to do carbon fusion and the whole thing just goes kaboom and you get this wonderful standard candle the astronomers use to measure the size of the universe.
Pamela: And there’s different kinds of supernova. All give off their own signature display where you get one set of elements being brought into creation by a Type 1a. Another set of elements being brought into creation by a Type II, by a Type 1c. All of these different kinds because they have distinct nuclear reactions that go on produce a distinct set of elements and also related elemental lines in their spectre.
Fraser: Right. Okay, so Type 1a supernova, exploding white dwarf ruled out. So, now we’re looking at a Type II supernova, but why did they not think that it was a core collapsed supernova? Why didn’t they think it was something – I mean it was more energy than the brightest supernova that had ever been seen, so couldn’t that just be like a monster star that core collapsed?
Pamela: Well, so, they initially did think that it was a monster star that had core collapsed. Now, the issue became a few hundred days after its initial explosion, when they were looking at it, what they saw was it had, one, decreased in mass – not mass, decreased in luminosity in ways that didn’t match with the Type II model.
The other thing that they saw was this spectre had a bunch of really weird atomic lines in it that for a long time scientists couldn’t figure out. And it was only in a recent paper by Anders Jerkstrand, Keiichi Maeda, and Koji Kawabata, that they were able to piece together that these really weird atomic lines that were coming from the area of excited material around that supernova explosion were neutral iron.
Fraser: Okay. What’s wrong with neutral iron?
Pamela: Well, neutral means that your little happy iron atom hasn’t had any of its electrons stripped off. And you’re always gonna have some of that hanging out around a supernova, but the strength of these lines corresponded to half a solar mass or so, between a third and a half a solar mass of iron in the vicinity around this star.
And that amount of iron at the temperature that made sense with neutral iron isn’t something that you’re gonna get with core collapsed star. The temperature was off.
Fraser: Okay, right. And so, astronomers now had to – because originally they were thinking that it was something like Anacarana, right?
Pamela: Yeah.
Fraser: Like, there was gonna be a star with a 100 to 200 times the mass of the sun had exploded. And as you said, they looked at it and it was visually bright. But like when they looked at it with, say, the Chandra X-ray Observatory, it wasn’t intrinsically x-ray bright in the way that you would expect one of these monstrous stars. So, it’s always this mystery.
Okay, so now you see all of this neutral iron in the vicinity, so what does that mean?
Pamela: Well, so that seems to imply – well, expletive. The only way you get that is with that Type 1a supernova that we were talking about.
Fraser: Wait, we just ruled that out.
Pamela: Right. And this is the problem. And this is a very short and brilliant research paper that pieced together a lot of the research about this to come to a really clean conclusion. So, looking at this and seeing, wow, there must have been all of this material that came out of this. How do you do that? What is the temperature that corresponds to it? Well, what they looked at was – and here I’m gonna read from the paper.
A core collapsed supernova would produce too little, and I’m paraphrasing, too little nickel. It would only have produced a tenth of the solar mass of nickel that would have then decayed via cobalt to form that iron. So, it can’t be that and it couldn’t have expelled that much mass.
And so, if you instead look at, well, what about a pair-instability type explosion? Well, they’re you get –
Fraser: Which is a variety of those super mega heavy stars.
Pamela: Right.
Fraser: Where they get to a different kind of – essentially, from what I understand, it’s like they get to a point where they contract inward almost in a moment and then bounce as a supernova and tear themselves apart completely.
Pamela: Right. And to get what they were seeing would have required a 90 solar mass helium core.
Fraser: Right.
Pamela: And that’s not a thing, really.
Fraser: Right, okay.
Pamela: So, that didn’t work. So, how do you get this much energy out of a white dwarf, which is the only way they could explain the amount of iron they were seeing.
Fraser: Okay, okay. What do they propose? What do they think happened?
Pamela: Kinetic energy.
Fraser: Kinetic energy?
Pamela: So, you have all the energy that is in the mass of the star. That’s contributing to the supernova. That’s what we’re used to in the Type 1a. But if you have a fastmoving white dwarf star that has kinetic energy, this is the same kind of energy that causes massive craters to form when asteroids strike objects. It’s that kinetic energy getting transferred into other forms of energy. It causes things to go boom.
Well, in this case what we’re seeing is a white dwarf in a binary system that is undergoing a merger. So, here it’s like we’re gonna pull up every possible bell and whistle to make this happen.
Fraser: Right. This is the most extreme, bizarre, crazy system you can possibly imagine.
Pamela: This is awesome.
Fraser: Yep.
Pamela: And as the white dwarf goes into the envelope of its companion star, which is just a like regular giant star.
Fraser: Right, like a red giant star.
Pamela: Yeah.
Fraser: Of what our sun will do when it dies.
Pamela: It is able to shed out all of this material from the outer envelope to make a tight circumstellar medium around the star.
Fraser: I’m imagining a – sorry, like I’m imagining like a car tire going through a mud puddle. Right?
Pamela: Or the way I imagine it –
Fraser: Right? Or just like spraying out water as it’s just carving through this puddle.
Pamela: So, maybe because I’m a woman, I think of it as stirring something too quickly and you spray material in all directions. So, you have this white dwarf plowing through the outer layer of its companion. They’re now like a single shared envelope system; it’s in the process of merging. And somewhere along the lines this white dwarf star is like and there’s too much mass on me.
Fraser: Right. But that’s what they do, right? I mean that’s how you get a Type 1a supernova is you feed a white dwarf 1.4 times the mass of the sun slowly, carefully, and then it finally explodes. But in this case it just – it was force fed as it dove through the envelope of this red –
Pamela: And it got so much angular momentum.
Fraser: Right.
Pamela: So much angular momentum.
Fraser: Right.
Pamela: And it’s the transfer of angular momentum and the shedding of its orbital velocity. All of this energy was where all that excess energy came from. And so, this raises this fascinating, well, expletive. Part of the variation that we’re gonna see in Type 1a supernova is going to be driven by are they – what is their velocity energy that they’re getting rid of? What is this kinetic energy that’s going into these explosions?
Fraser: Oh, so you think this might have implications for using white dwarfs as standard candles just in general?
Pamela: Yeah.
Fraser: Hmm, interesting.
Pamela: So, one of the things they hint at is this could be an explanation for other weird supernova we haven’t been able to understand. And if we’re seeing on a regular basis, by which I mean it’s astronomy. If you see something six times, it’s a trend.
So, if we’re seeing this ever so rarely with this huge and dramatic effect, how often are those small deviations from the mean caused not just by the environment that the star is in, but by also the energy that is in the star system. We know all of these are binary. That’s how they happen.
Fraser: Right, right. We know that white dwarfs exploding as Type 1a supernova, which is the standard candle, they are all a – each one of them is a, as I said, you’re sipping away at some of the star’s juice and eventually you explode.
Pamela: And so, if you start –
Fraser: Oh, go ahead.
Pamela: — with the idea that the standard candle means every single one of these should explode with the same luminosity, the same number of lumens, that same candle brightness, but then it turns out that sometimes they have this secondary source of energy, that adds a fascinating source of noise.
Fraser: Right, absolutely.
Pamela: And so, I love the implications of this research.
Fraser: Right. And so, when you think of how astronomers are using these standard candles to measure the distance to various galaxies across the universe and of course the finding that these stars are farther away than they should have been, then this is dark energy. I mean this whole idea of dark energy. Although, I mean it’s exciting, but then at the same time you would expect it to be random, right?
Pamela: Yes.
Fraser: There wouldn’t be some reason why the stars that are farther away are extra far away while the stars that are closer are not. Like, you wouldn’t have that direct correlation between them –
Pamela: Right.
Fraser: — feeding in strange ways, but you would definitely – it could definitely have an implication on just your understanding of what – how bright these standard candles are.
Pamela: And this is a random source of noise. And you have to assume that while it may not be equal on both sides of the skew, there’s probably not a reason that it would change over the history of the universe.
I wouldn’t be surprised if we see dark energy go away as our research evolves because we are finding that there are systemic effects where the populations that white dwarfs are forming from change over time. And we’re starting to see hints that different populations of stars produce white dwarfs of different luminosities. This isn’t the effect that’s gonna make dark energy go away.
Fraser: Right.
Pamela: This is just gonna create noise in our measurements that is gonna make measuring those other effects that much more difficult.
Fraser: Right. But it is gonna be awesome noise. So, just to sort of like rewind and sort of understand this story, right? You had these two happy stars in a binary relationship, two main sequence stars, one was a little more massive than the other. And at some point, the more massive star died.
Pamela: Yes.
Fraser: Bloated up as a white dwarf, puffed out its outer layers, and then – puffed out as a red giant, sorry, bloated up, threw out all its outer layers, and then collapsed down into a white dwarf. And I guess by doing so it sort of changed the gravity dynamics of the system. And so now you’ve got a white dwarf orbiting around a main sequence star and then X billion years later the second star puffs out as a red giant, eats the white dwarf, the white dwarf just careens into it, gobbles up enough mass. And apparently it only took like a hundred years.
Pamela: Yeah. That was awesome.
Fraser: When this actually happened. Yeah. And then it wrecked the star. So, it’s not like it sort of plunged in and just sort of gently faded away down to the core of the star. It just – you know like I said, like a car going through a mud puddle or – someone mentioned in the chat, right, turning on your blender without the lid.
Pamela: And what’s kind of cool is they can actually use that iron – the iron lines keeping so important. So, they were able to figure out when the circumstellar material must have been admitted to get all the velocities of everything going correctly. And so, they figured out that that must have been emitted in the past 100 to 200 years.
So, that actually – they went from thinking that the merger took between 10-ish order of to 200-ish order of years. But then you look at that iron and that material that would have been created by the infalling white dwarf. And that tells you that this was a hyper giant because of the infall times for the different kinds of scenarios. So, they were able to figure out what the white dwarf fell into by when that circumstellar material was put into place.
Fraser: And so when you’ve got this white dwarf star exploding in the wreckage that it caused as it spirals into the red giant, then the energy and the material blasting out of this white dwarf collided with this material and that’s what caused the brightness, that’s what caused the luminosity is the collision between the white dwarf and the material around it?
Pamela: That’s what caused the iron that we saw. So, the brightness of the supernova came from you have a white dwarf star that is flying around inside what’s called a common envelope. So, you have a star that now has two nuclei. One that is that hyper giant, it started out there nuclei. And the other that is this infalling white dwarf. And it is the combined kinetic energy of the white dwarf and the mass energy of the white dwarf that goes into all of the nuclear kaboom parts. That combined kinetic energy and the regular kaboom energy, that’s what created the amazing –
Fraser: Right, okay, okay.
Pamela: — initial luminosity. It radically faded so that when they were looking at it 400 days later, it was 100 times less bright than expected.
Fraser: Right.
Pamela: And what they were seeing at that part of the time was the illuminated material that had been shed, which included the neutral iron lights.
Fraser: So, a better analogy might be like when two black holes collide with each other and you get this gravitational waves and people say ten times the mass of the sun was released in gravitational waves. It’s not like the black holes got less massive. It’s that the kinetic energy of their collisions was turned into the gravitational waves that rippled throughout the universe. And so, in a similar situation you’ve got the kinetic energy from this white dwarf spiraling inward that is then able to translate that into additional energy, an extra one/two punch for its supernova.
Pamela: And one of my favorite parts about this paper is I was extremely eager after hearing the question from one of our audience members Bad Panda Bear. He asked, well, what was the result of this? And in trying to find out, the authors of the paper were like, we haven’t been able to bottle situations like this. They’re just too complicated.
Fraser: But did the red giant exist after the white dwarf exploded?
Pamela: Can’t tell yet.
Fraser: Yeah.
Pamela: And so, this is a class of objects. This isn’t just one object. This is a class of objects shared common envelope systems, merging binaries that go boom. And in some cases the going boom is gonna be mediated by gravitational waves, in some cases it’s just gonna go boom, and trying to understand the timing of this, how quickly they go, how slowly they go, what’s left. We need better computers.
Fraser: Yeah.
Pamela: So, they’re still more to come on stories like this.
Fraser: Right.
Pamela: We don’t yet know how this one ends. We just are understanding how it began.
Fraser: Or way bigger telescopes because this thing is tens of millions of lightyears away.
Pamela: Well –
Fraser: So, there’s no observing it, right? There’s only – there’s observing the explosion, but you can’t point a telescope with that level of precision to see what’s there now or what was there before.
Pamela: Once the nebula gets a little bit bigger you’ll be able to see what’s left in the center.
Fraser: Oh, good point.
Pamela: We’re just not there yet.
Fraser: Yeah, yeah. So, James Webb, this will be one of your future targets.
Pamela: Oh, you’re so optimistic.
Fraser: But it’s great when you think about – it’s gonna launch. It’s so great when you think about just all of these combinations that there are every – you can mix and match black holes, neutron stars, white dwarfs, red giants, super giants, in every combination.
Pamela: Black holes do not form common envelope stars.
Fraser: No, but they sure can – what happens if they hit one, right? Like, I mean the point is something is observed when these monsters interact with each other.
Pamela: Yes.
Fraser: And so right now you’ve sort of got, on the one hand, you’ve got this imaginary collection of different ways these different objects can come together. And on the other hand, you’ve got all of these observations that are across this entire spectrum of what people have seen. And it’s like this mix and match where you’re like, okay, is this that, is that this? And so I look forward to them continuing to try to figure out which causes what.
Pamela: And the cool thing that we’re just starting to statistically learn – and this is the last cool thing for today, I promise. We’re finding that more binaries than we used to think become binaries late in life. So, you can have systems that have an involved low mass companion and then not yet evolved high mass star.
Fraser: Right.
Pamela: And so this potential of having white dwarfs around truly massive stars is gonna lead to even a larger diversity of objects being possible.
Fraser: So cool. Pamela, do you have some names for us to celebrate here on Astronomy Cast?
Pamela: I do. Astronomy Cast is entirely a listener supported podcast. We are here because of you, you and your patronage on Patreon.com/Astronomy Cast allow us to pay our servers, pay our software, and pay our Susie. So, thank you for everything you do.
And this week I’d like to thank Bryan Kilby, Jessica Phelts, Omar Del Riverio, William Loward, Joe Wilkinson, Bruno Lets, Marco Larosie, Dustin A. Ralph, Mark Grundy, J. Alex Anderson, Jeremy Kirwin, Mark Steven Rasdack, Tim Garrish, Paul L. Hayden, Brent Kronop, Eron Sigev, Arthur Latts Hall, William Anders, Jack, Joshua Pierson, Justin Proctor, Fredick Saje, Claudia Mastrioni, Rachel Frye, David Gates, Dwayne Isaac, and Thomas Tubman.
Thank you all. You make us happen.
Fraser: Thanks everybody and we’ll see you all next week.
Pamela: Buh-bye.
Female Speaker: Thank you for listening to Astronomy Cast, a nonprofit resource provided by the Planetary of Science Institute, Fraser Cane, and Doctor Pamela Gay. You can find show notes and transcripts for every episode at Astronomy Cast. You can email us at Info@AstronomyCast.com. Tweet us @AstronomyCast, like us on Facebook, and watch us on YouTube.
We record our show live on YouTube every Friday at 3:00 p.m. Eastern, 12:00 p.m. Pacific, or 1900 UTC. Our intro music was provided by David Joseph Wesley. The outro music is by Travis Sorrow and the show was edited by Susie Murph.
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Duration: 31 minutes
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