Modern astronomy has found that the Universe can surprise us. Here’s one which astronomers have called Luminous Fast Blue Optical Transients. They’re kinda like supernovas, they’re kind of like gamma ray bursts, but they’re not like them. So what are they? In the distant Universe, are blue light flashes, bright and hard to understand. These objects, uncreatively named "Luminous Fast Blue Optical Transients," are just the kind of puzzle astronomers love. In this episode, we look at their discovery and our current understanding of what they might be.
Show Notes* Discovery of a new class of transients: Luminous Fast Blue Optical Transients (LFBOTs) * First major example: AT2018COW (“The Cow”) * Extreme brightness: up to 10⁴⁴ ergs/sec, rivaling the most energetic explosions * Brightest recent case: AT2024WPP (“The Wasp”) * How LFBOTs differ from supernovae and gamma-ray bursts * Role of the Zwicky Transient Facility (ZTF) in discovering fast transients * Possible origins: + Black holes consuming Wolf-Rayet stars + Tidal Disruption Events (TDEs) + Stellar-mass black hole interactions * Connection to gamma-ray burst classifications (short vs long) * Binary star systems and extreme stellar evolution pathways * Impact of black hole activity on surrounding star and planet formation * Need for future UV and next-generation observatories * Growing statistical samples to better understand black hole feeding behavior * Humorous nickname proposal: “Blooper Novas” * Patron appreciation and episode close
TranscriptFraser Cain:
Astronomy Cast, Episode 782 Luminous, Fast, Blue Optical Transition. 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, I'm the 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 are you doing?
Dr. Pamela Gay:
We have our first sign of spring, the snowballs, the little tiny white bulbs have come up. They have bloomed. Mine haven't.
They've come through the snow, which is what they're supposed to do. And so we've had our first bulbs of spring.
Fraser Cain:
Yeah, we haven't had those yet. All of my bulbs are sort of peeking through the ground now, through the ground layer, but no flowers yet. But I'm probably just a week or two away.
And flowers on my trees, on my cherry trees. So I'm looking forward to that. Modern astronomy has found new ways that the Universe can surprise us.
Here's one which astronomers have called Luminous Fast Blue Optical Transits. They're kind of like supernova, they're kind of like gamma ray bursts, but they're not like them. So what are they?
So I guess, set the stage, when and how did astronomers, it started to dawn on them there was an entirely new class of objects out there in the Universe. And we need to also come up with an acronym or a better name for this, but maybe we'll do that later.
Dr. Pamela Gay:
All right. So back in 2018, folks looking through ATLAS and Hong Kong Observatory data followed up on a transient from the Zwicky Transient Facility. So it was found in this other data set.
It was backtracked to being in the Zwicky data set. And it was cataloged, I kid you not, as AT2018COW.
Fraser Cain:
The cow.
Dr. Pamela Gay:
The cow.
Fraser Cain:
Right. It sounds like a call sign for a radio station.
Dr. Pamela Gay:
And I just love the fact that this stuff just serendipitously happens because of how we name these transients. We just cycle through the alphabet over and over and over. And it turns out the Zwicky Transient Facility is out there doing an obscene amount of transient discoveries that is not getting discussed.
They are able to prototype a whole lot of the data pipelines that are going to be used for the Rubin Observatory using the Zwicky Transient Facility because it is finding supernova after supernova, moving object after moving object, weirdo blue thing in the sky after weirdo blue thing in the sky. And the cow.
Fraser Cain:
Yes.
Dr. Pamela Gay:
The cow.
Fraser Cain:
The cow.
Dr. Pamela Gay:
The cow.
Fraser Cain:
2018, the cow. Yeah.
Dr. Pamela Gay:
It was an object that put out more light than any supernova thus far seen, which was not on anyone's bingo card.
Fraser Cain:
That's impressive.
Dr. Pamela Gay:
Yeah. Yeah. 10 to the 44 ergs per second.
Fraser Cain:Now that's how you describe a lot of energy. You got to stay in ergs. Now we're talking.
It's true. It's true.
Dr. Pamela Gay:And so there was a whole lot of what on earth could cause this confusion and hopes that there would be more. And the sky did not disappoint. And for the first time in my career, neither did the names.
I'm going to be stupidly excited about the names of these things because astronomers generically are really, really bad at naming things. But the next one that was found was ZTF, Zwicky Transient Facility, 18 ABV, the ABV is very boring, KWLA, which became koala. Right.
So, so this one was also in 2018 and it was documented to reach 40,000 degrees Kelvin. They didn't have a clear distance to it, so they didn't initially have clear luminosity to it. They just knew it was really, really hot, really hot.
Fraser Cain:And since then, I mean, we have found probably about 10 of these objects and, and clearly some the, the astronomers that studies are delighted because as you said, they're giving them silly names based on a kind of a rough correlation of what the gobbledygook alphanumeric code ends up being close to those animals.
Dr. Pamela Gay:
So ZTF 20 ACIG MEL, so there is a C and there is an MEL, it became the camel, then we have 2023 FHN became either the finch or the fawn. And the most important one, I think for today's discussion is AT 2024 WPP, the wasp, right?
Fraser Cain:
And this is the brightest one that has ever been seen.
Dr. Pamela Gay:
Yeah. Yes.
Fraser Cain:
Okay. So, so that's great. And so give us a sense of the characteristics of the explosion.
What makes it so much different than say a supernova or a gamma ray burst?
Dr. Pamela Gay:
So this is something that for just a matter of weeks, peaks in brightness, extremely in the blue, extremely, extremely in the blue. So we're talking super hot, and it's also putting out an indescribably large amount of energy. Like this thing is common for you.
It is the wasp, the most powerful one, put out the equivalent of take 10% of the sun's mass and just turn it into energy. And that's how much energy it put out.
Fraser Cain:
Wow. Like E equals MC squared, just convert that matter into energy.
Dr. Pamela Gay:
Just straight to energy. It's not messing around. It's just like, I'm here, I'm blue, I am hot.
I have energy.
Fraser Cain:
But when we think about say gamma ray bursts, right, we have the short and long gamma ray bursts where it's sort of like the two second mark. If it's less than two seconds, that's a short gamma ray burst. And those appear to be colliding neutron stars.
If it's long, then it's a long gamma ray burst. And those are hundreds of seconds. Yeah.
And they can be much, two seconds or longer, but yeah, it can be hundreds of seconds. And that is a core collapse supernova. And that's different from the gamma ray bursts.
Yeah. These are like 20 days. Right.
And, and, and like, why do astronomers think that they are not either gamma ray bursts or supernova?
Dr. Pamela Gay:
So the, the gamma ray bursts, they, they just don't fit with any of the gamma ray bursts that we're seeing. They're, they're not showing up in Fermi data the same way that gamma ray bursts do. And if you don't look and smell like a gamma ray burst, you probably aren't a gamma ray burst.
But then the amount of energy that's coming out of them is just so much greater than what we've seen from supernovae that initially they were like thinking, maybe there's some kind of super luminous supernovae. These are some kind of supernovae we haven't seen before. And so people went with that theory as one possibility.
Then there was the, maybe this is something that's getting shredded, something that's getting destroyed, something that, that's getting converted from mass to energy and went down that rabbit hole as well. So there are all these options and we just needed more data.
Fraser Cain:
Right. And, and we have more data. So you know, we did a flurry of reporting on this at Universe Today in the last couple of months or so, um, where it looks like astronomers think they're starting to settle in on an explanation.
Dr. Pamela Gay:
It's true.
Fraser Cain:
And, and it's really cool because again, remember you're a budding super villain, Pamela.
Dr. Pamela Gay:
I know.
Fraser Cain:
So when you say something is really cool, other people should say, is this causing the entire destruction of a large volume of space? Yes. Yes.
Dr. Pamela Gay:I, yeah.
Fraser Cain:
Yeah. Yeah. Just remember, Pamela is a super villain, which is something that's cool.
You should be afraid. All right. She loves, she loves super volcanoes.
This is, this is what we're talking about here. But yes, it is super cool.
Dr. Pamela Gay:
All right. So sometimes one answer can encompass a spectrum of behaviors. And so in this case, it's looking like what's happening is you have stellar mass black holes for some value of stellar mass that are consuming gas, consuming stars, shredding neighbors with the wasp, the most powerful of these thus far seen, probably being a roughly 10 solar mass black hole being orbited by a Wolf Ray A star.
So something young that when these two stars were on, when they were zero age main sequence stars, the one that's currently a 10 solar mass black hole was the bigger of the two stars. The Wolf Ray A was the smaller of the two stars. And had it been allowed to live, they would have ended up being a binary black hole system someday.
However, instead, the Wolf Ray A star got too close to the black hole. There's lots of different things that can cause stars to migrate together. And it appears that a chunk of material was torn off the Wolf Ray A star as it was disrupted.
And that chunk of material, again, roughly 10% the mass of the sun. It just became energy.
Fraser Cain:
Yeah.
Dr. Pamela Gay:
As you do. As you do.
Fraser Cain:
Right. Right. So, so one thing, just to clarify, you said Wolf Ray A stars are young.
They are, they're an evolved form of stars. They're, they're so, so it's a star where they've gone through the main sequence phase. Now they've sort of blown away a lot of their outer layers, but they're, but they're massive and, and going to explode.
Dr. Pamela Gay:
And this is one of those times where adjectives are, are not what we should be using because a Wolf Ray A star has an age that's still measured using millions and billions. And so in my brain, it never becomes old. It dies young.
Fraser Cain:
Dies young. Yeah.
Dr. Pamela Gay:
And, and so, so basically they become angry teenagers and die.
Fraser Cain:
Yeah. Now again, super villain, Pamela just described that event in very clinical terms. So allow me to sort of describe the true horror of what just happened here.
You've got a black hole, 10 times the mass of sun orbited by another massive, very massive star. The star got too close and the black hole tore off. It disrupted it.
A huge chunk of that star and just nommed it away, causing this extremely bright flash. And you got this, you know, this bright blue ultraviolet flash coming from this, this object. And it appears that these, these blue optical transits are caused when stars are dismembered by black holes.
Dr. Pamela Gay:
And, and there's still the potential that this could be clouds of material getting consumed. That is not eliminated. These things come in a variety of brightnesses.
They behave slightly differently. Not all of them are going to be Wolf Ray A stars getting disrupted, which is magnificent when it does occur. But we can imagine, we've, we've lately, there has been this amazing rash of really weird stuff getting found.
So there was recently a star found that had what appears to be two planets collided and formed a giant disc around a settling together, super Jupiter. And we've seen before with, I think it was Epsilon and Regi where you have a binary system that has a protoplanetary disc around the companion star. So we can imagine seeing these kinds of luminous fast blue optical transients in systems where there there's material that hasn't formed into a star yet.
What we know for certain is these things appear to consistently occur in galaxies with a large amount of star formation going on in galaxies where you expect to see massive stars still living and breathing until they get shredded by their neighbor. And it's these kinds of systems that allow stars with ages in the millions instead of the billions to exist where we're seeing these events occurring. So again, it's massive stars getting disrupted, but there's the potential also for neighboring stars to lose their planetary discs as they get eaten before life can form.
Fraser Cain:
And it's interesting to sort of see, like we have seen various flavors of black holes consuming stars across the universe, but generally it's in the, a supermassive black hole just tore a star apart and the supermassive black hole already has accretion disc around it. And this was a minor addition to the overall luminosity that is coming from the black hole. Or we get this situation, we talked about this I think last week or a couple of weeks ago, that you can have black holes or even stars passing through the accretion disc around a supermassive black hole and then you get that flash.
But this is much more, you know, that's like a giant stepping on a bug. This is sort of, I don't know, to use the analogy, like a tiger taking down something that's, you know, bigger than it, an elephant, right?
Dr. Pamela Gay:
I mean, the thing about this is this had the potential to be a black hole, black hole system that we would later see merge, not us, we'll be dead. Someone would eventually see merge with gravitational waves being released into a larger black hole. But this was literally a tensile or mass black hole saying, nope, you don't get to be like me.
You shall be my dinner.
Fraser Cain:
Right. And so is it doomed? Like there was like now it's just, it's going to be meal after meal after meal until it's gone into the accretion disc and then into the black hole and it'll never get that chance to detonate on its own as a supernova.
Dr. Pamela Gay:
Exactly.
Fraser Cain:
Wow.
Dr. Pamela Gay:
Yeah.
Fraser Cain:
Yeah. Awesome. Again.
I mean, although I think that works, you know, it was awesome in that it is feel it will fill you with awe to watch it. Yes. To Slackjaw.
So first we got to deal with one other issue here, which is the name.
Dr. Pamela Gay:
Yeah. It's terrible.
Fraser Cain:
It's terrible. It's luminous. I don't even remember.
Hold on.
Dr. Pamela Gay:
Look this up. Okay.
Fraser Cain:
Okay. But the acronym is no better. And astronomers genuinely are usually pretty good at this.
So it's LFBOT. LFBOT. It's terrible.
It's terrible. They named the objects well. So I asked my audience to come up with some better names and my favorite so far is a blooper nova.
What do you think?
Dr. Pamela Gay:
Yes. Yes, please.
Fraser Cain:
Yes. All right. So astronomers, if you're listening, that is the name.
They're not LFBOTs, right? They are blooper novas. So then what does the future hold for the system then?
Dr. Pamela Gay:
So this particular system, I mean, it's not possible to say with any certainty exactly how things die. We're not there as a profession yet. But over timescales, I'm not going to guess, chunks are going to get consumed.
There will be additional luminous blue goodness as this disrupted object forms potentially a disk as it potentially has jets. We've seen jets in other situations. It's the case of it's dying.
It has to shed its angular momentum. There's going to end up being a disk at some point. Disks like to build magnetic fields.
Those like to build jets. It's going to do the black holes eat things and it looks the same no matter what the scale is. But what's cool is we're entering an age where we just started finding these less than 10 years ago and we're able to find it because of the Zwicky transient facility.
It's a fairly large scope. It's out there just going bang, bang, bang, looking at the sky, looking for things that twinkle, flit, flare, move in the night.
Fraser Cain:
Oh, I wonder if there's like another observatory that's just about to come online that's going to do that.
Dr. Pamela Gay:
Southern hemisphere maybe? So that new pipeline that is going to be able to see even more starbursting galaxies, which are much more common in the early universe. You get that bigger mirror.
You're going to be able to see things, resolve things further out. You're going to be able to see more of these in its great depths. And so I am hoping that the things that we've started to learn exist, thanks to the Zwicky transient facility.
We're going to get statistically significant samples of that explore the whole, here's the span of luminosities. Here is the span of periodicities. Here is one that's recurring.
Here is five that have jets that as we find more and more of them, we're going to start to understand all the ways that black holes eat their neighbors. And we're used to seeing this kind of consumption and cataclysmic variables, which is on our list of shows we need to do. But we needed to do this show first because there is an object called the cow.
Right. And that is excellent.
Fraser Cain:
Yeah. Yeah. I mean, you mentioned Vera Rubin and there's actually a couple of ultraviolet observatories that are going to be coming online.
And this is a tricky one because the wavelengths that you need to be able to detect this, you need to be in space. You need a space telescope. And that there are a couple of ultraviolet observatories in the works right now that should get us to this place where we can start to observe these on a regular basis.
Do fall on observations and cross compare with what Vera Rubin is finding. And it's expected that we should get dozens of these every year. And then you can really break them down and say, okay, you know, these are the ones where it's a Wolf-Reye star, but maybe these are the ones where it's a regular star or a main sequence star, or it just ate a red dwarf or whatever that, that, that, that, you know, we know that massive stars tend to come in multiple star systems.
And so then what is the trajectory of those star systems? Do you get two black holes orbiting each other, which then merge, do you get neutron stars that merge? Do you get a white, two white dwarfs that eventually merge?
Do you get white dwarfs that consume off of a companion star and then you get a type one a supernova? Do you get a black hole that consumes its companion or do you just get two stars that are far away and they just never do anything mean to each other at all?
Dr. Pamela Gay:
So the thing that I'm hoping that we see is we, we have hints that hypernova that generate long duration gamma ray bursts are potentially a binary system where the massive star goes supernova onto a compact neighbor that has given it extra angular momentum. And so we're going to be seeing potentially systems that that compact neighbor is not just a neutron star, it's a black hole. And as you go supernova, that material goes and gets eaten.
And, and, and these are low probability objects. The most massive objects are the most rare. The initial mass function of stars is like not very many super bright ones, lots and lots and lots and lots of these really faint ones.
And then we're just left with a universe of uninteresting little tiny red stars that like to bake their baby planets. The more sample size we have, the higher the likelihood we're going to start seeing these long duration gamma ray bursts to understand what's going on and start seeing them in more and more kinds of pairs. And it's just awesome.
[Speaker 5]
Yep. Yep.
Fraser Cain:
I mean, and, and that's the part that I really love. I mean, you know, to go down a totally different rabbit hole, we're sort of moving into the same regime with exoplanets and their atmospheres. I mean, you know, we only, we know of say 6,000 exoplanets, but we only have a few dozen that their atmospheres have even been imaged, none that are earth-sized, you know, around red dwarfs or around sun-like stars.
And so we don't know what's normal yet. We don't know what is the, how these things evolve. And when new telescopes come online, they will get these larger data and eventually we will be, you know, we will know tens of thousands, hundreds of thousands, millions of planetary systems, and we will understand in this very rich way.
And then we will be able to do the same for the future of star systems that we can look out and have enough of the universe in our minds at one time that we will understand how things work, how things play out, what the future evolution looks like, what the past looks like. It's a, it's a very cool direction that we're heading in. And a lot of these big tools, especially Vera Rubin are going to get us huge steps forward.
So any day now. So just one last reminder, everybody, blooper novas.
Dr. Pamela Gay:
Okay. We seriously need to figure out who to write to because that is excellent.
Fraser Cain: Yeah. But we just do, you don't write to anybody. You just start saying the word until it sticks.
Dr. Pamela Gay:
I like that.
Fraser Cain:
All right. Thanks, Pamela.
Dr. Pamela Gay:
Thank you, Fraser. And thank you so much to everyone out on Patreon who is supporting us at patreon.com slash astronomy cast this week. We would like to thank the following $10 a month and up patrons, Adam and he's Brown, Alex rain, Andrew palestra and to sore Astro Bob, Bart Flaherty, Benjamin Davies, Bob Zatsky, Bresnik, Brian Cagle, Bruce Amazine, Kami Rassian, Cody Rose, Dale Alexander, David, David Green, D's Astrina, Dr. Jeff Collins, Elliot Walker, evil Melky, Felix Gute, Frank Stewart, galactic president, scooper star McScoops, a lot, Glenn Phelps, Gordon Dewis, Gregory Singleton, Helga Bjorkog, James Signovich, Jason Kwong, Jeff Wilson, Jim Schooler, Joe Holstein, John Drake, John phase, Gordon, Jordan Turner, Justin s, Katie and Ulysses, Kim Baron, Kinsaia, Penflanko, Laura Kettleson, Lou Zealand, Mark Masa, Haleu, Matthew Horstman, Michael Prashada, Michael Regan, Mike Hosey, Nick Boyd, Papa hot dog, Paul L Hayden, Philip Grand, Randall, R3, Robert Cordova, Ron Thorson, Ruzzard with a Z, Sage Sinfin, Chersem, Scott Briggs, Sergei Manilov, Slug, Stephen Miller, The Big Squish Squash, Thomas Gazzetta, Time Lord Iroh, Tushar Nakini, Wanderer M101, William Andrews. Thank you all so very much.
Fraser Cain:
All right. Thanks, everyone. And we will see you next week.
Dr. Pamela Gay:
Bye-bye.
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