Ep. 475: Fast Radio Bursts

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You know what’s fun? Mysteries. Here’s one: fast radio bursts. Astronomers have been detecting mysterious one-time signals from across the sky. What’s causing them? Nobody knows for sure, but the search is on to get to the bottom of them.
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Show Notes

Fast Radio Bursts
Duncan Lorimer and his student David Narkevic – Lorimer Burst
Parkes Observatory
interferometer UTMOST
Paul Scholz at McGill University
Green Bank Telescope
Breakthrough Listen
Canadian Hydrogen Intensity Mapping Experiment (CHIME)


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Fraser Cain: Hey, everyone. Fraser here. Have you got vacation plans for September? If you’re looking for an adventure, why not join me and Dr. Paul Sutter as we explore the eastern Caribbean in September 2018? The trip begins September 20th with a tour of the Kennedy Space Center in Florida, and that’s where you’ll see the mighty Saturn 5 rocket, the space shuttle Atlantis, and so much more. This is space nerd headquarters. So, if you’ve never been to the space coast, you really need to get this off your bucket list. I’ve been twice now, and it’s absolutely one of my favorite air and space museums in the world.
And then we’re on the boat for seven days touring Mexico, Roatan, and Belize during the days where we’ll see wildlife, ruins, and amazing culture. Every night, we’ll be doing stargazing on the deck of the ship, hanging out, and having fun. And we’ll be recording live versions of My Guide to Space, and Paul’s Ask a Spaceman series. Then we return on September 28th. So, all you need to do to book a reservation before April 1st and make a small deposit, and then you’re signed up with us. But hey, you need a vacation anyway.
Why not hang out with us, see the sights, enjoy the skies, and spend time with likeminded space geeks and make new friends from around the world. So, that sounds like fun. Head on over to astrotours.co/seastars. And if this doesn’t work for your schedule, no problem. Paul’s leading a group to the Atacama Dark Skies of Chile in December. And then we’re gonna be leading a tour to Costa Rica in March 2019. And if we can get totally organized, we wanna chase the total solar eclipse in Chile for 2019. Gotta see them all. Thanks!
Astronomy Cast Episode 475, Fast Radio Bursts. 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. My name is Fraser Cain. I’m the publisher of Universe Today. With me is Dr. Pamela Gay, the director of technology and citizen science at the Astronomical Society of the Pacific and the director of CosmoQuest. Hey, Pamela. How are you doing?
Dr. Pamela Gay: I’m doing well. How are you doing, Fraser?
Fraser Cain: Doing great. I’ve got a couple of things that I have to shamelessly self-promote. And that is I was a guest on the Decipher Scifi podcast last week, and we talked about Black Mirror. So, I got a chance to just go off the rails on three episodes of Black Mirror and tell people what I thought for the first, “The USS Callister,” which is probably my favorite Black Mirror episode ever, and then two others, “Archangel” and “Crocodile.” So, one, as a helicopter parent, hit me right between the eyes.
Dr. Pamela Gay: Yeah. That one was terrifying.
Fraser Cain: Yeah. And then the other one was like, “Eh. It’s all right.”
Dr. Pamela Gay: I don’t think I got to that one yet.
Fraser Cain: It had some stuff that we thought was a pretty clever idea. Anyway, so if you wanna hear me not talk about space and astronomy and instead nerd out about sci-fi and Black Mirror, you should totally check out Decipher Scifi. And just search. I’m sure you can find it where all good podcasts are streamed.
Dr. Pamela Gay: Sounds good. Now, you said you had two things, and that was one.
Fraser Cain: No, no, no. I’m a little jumpy today, and it’s only because there’s an enormous amount of news coming out of the space and astronomy sphere. So many amazing stories all just broke today, and I don’t even know where to start. So, needless to say, there’s gonna be – check the news. It’s really interesting. That’s my second thing.
Dr. Pamela Gay: Don’t look at the political news because we’re aiming towards a government shut down which has me dead inside.
Fraser Cain: No. No, no. No. Space. Space news. Just the space news.
Dr. Pamela Gay: Okay. So, yes. All good things. Go to Universe Today. Read about them.
Fraser Cain: Yeah. All right. So, you know what’s fun? Mysteries. Here’s one. Fast radio bursts. Astronomers have been detecting mysterious one-time signals from across the sky. What’s causing them? Nobody knows for sure, but the search is on to get to the bottom of them. I love this mystery of fast radio bursts. I did a video on them about six months ago, so I feel like I kinda know what’s going on, but what are they? Or at least what has been detected so far?
Dr. Pamela Gay: So, I can tell you the observables. I can’t tell you what they are.
Fraser Cain: Right. Well, but we’ll speculate.
Dr. Pamela Gay: We can do that. So, what they are is for a handful of milliseconds, astronomers will utterly randomly detect a extraordinarily powerful burst of radio signal across a variety of different wavelengths. And this is very reminiscent to how we first started discovering gamma ray bursts, where there was this moment of huge energy followed by silence before you could actually get a telescope pointed at where the gamma rays were coming from. And just like with gamma rays, they are, as near as we can tell, randomly distributed across the sky. Now, the reason I say as much as we can tell is because you have to be pointed in the direction that they’re emitted from in order to detect them.
Gamma ray bursts are happy to be detected even if they’re beside directionally, your telescope. They’ll just blast through the telescope to be detected. Radio waves are a little more finicky. You have to actually be looking in the direction of the light. But as near as we can tell, they come from all directions.
Fraser Cain: And how were they detected in the first place? How did they turn up the first fast radio bursts and realize that this was a thing?
Dr. Pamela Gay: It turns out it was actually a student going through archival data in Australia. The person who it is named after of course is the advisor and not the student, as so often happens.
Fraser Cain: That seems familiar.
Dr. Pamela Gay: It is the way of things. As long as he didn’t get a Nobel Prize, I’m okay with this. Not really, but I’ll pretend.
Fraser Cain: Or they get to share it. They get to share it is how it works.
Dr. Pamela Gay: Yeah. So, it’s referred to as the Lorimer Burst after Duncan Lorimer, who assigned his student, David Narkovic – sorry, if you’re out there David. I don’t know how to actually say your last name. So, David was going through archival data that was taken by the park’s radio dish in Australia, and there was this weird burst that seems to have gone off on July 24th, 2001. It was five milliseconds in duration and vaguely in the direction of the Small Magellanic Cloud.
It was a few fingers off the edge. And they didn’t know what it was. They didn’t know exactly where it was other than in that direction. It seemed, given the brightness, that it probably wasn’t local because if it had, we would have seen lots of other things associated in that direction that we just didn’t see. So, it was sort of like, “Huh. There’s something going on here. Let’s look more.” And this is where people started looking more.
Fraser Cain: Right. And the problem with this burst and all of them, as you said, five milliseconds. So, a fraction of a fraction of a second. And then it’s gone forever. And the thing was, in the beginning, they didn’t seem to repeat like pulsars, like other things out there. And so, how do you go looking for something that comes and goes in five milliseconds?
Dr. Pamela Gay: Yeah. And I think we’ll get to that because folks have started trying to get to the bottom of that. So, the thing was, this first one was found by a student in archival data in 2007. And the next time someone actually flagged one wasn’t until 2012 when the Arecibo radio telescopes – so, these are like one at a time telescopes all over the world – confirmed that there appeared to be an extra-galactic origin to one vaguely in the direction of Oregia. So, now we have one that is being detected in the northern hemisphere. This was done by Paul Schultz of McGill University. So, now we have a Canadian.
Fraser Cain: Oh, this story’s gonna come back to Canada pretty heavily. So, stay tuned.
Dr. Pamela Gay: Yeah. It’s true. It’s true. Canada does amazing science.
Fraser Cain: But we have the perfect instrument here for both some sweet snowboard grinding and also detecting fast radio bursts. So, we’ll get to that.
Dr. Pamela Gay: One of those is more useful than the other for this particular episode. So, here we have another one of these fast bursts. And they started going through more and more of the archival data. And in 2015, going through this data, it got to the point that Paul had found ten of these in non-periodically repeating. So, it’s just like, “Here’s one. Here’s one. Here’s one.” And they all seem to have plasma dispersion associated with them. So, this means that they were seen across a wide variety of different wavelengths in a very characteristic fashion.
And this is where people start making up stuff to try and figure out what the heck this might be. And among the guesses is that maybe it’s some sort of a young rotating neutron star where there’s plasma interactions, or it’s a highly magnetized situation, again, neutron star. Here we have are magnetars to blame.
Fraser Cain: Right. So, can we just stop on that for one second? I just wanna understand that mechanism. With a traditional pulsar, which is essentially a neutron star – it’s a rapidly rotating star – it is firing out blasts of radio waves on a very regular basis. So, what is different from the radio waves put out by a pulsar neutron star, or in this case, how is it different from a fast radio burst?
Dr. Pamela Gay: So, when we have a pulsar, it’s not that the pulsar’s giving things off in bursts, it’s that the pulsar is rotating. And just like a lighthouse on a coast, when you have a rotating light, it appears to an observer who’s stationary to be blinking on and off as the light rotates into and out of view. With pulsars, you have the magnetic field of the pulsar out of alignment with the rotational access of the pulsar. And the earth has this too. The idea of a magnetic field not being aligned with the rotation of an object, there’s nothing weird about that.
But with the magnetic field out of alignment, every time that pole of the magnetic field is pointed towards us, we get a burst because we can see down the mouth of the magnetic field. And that’s the pulse. Now, we have a continuous beam that is nothing more than we’re seeing the field and its interactions. With this, it’s as though periodically, something interacts with that magnetic field.
Fraser Cain: Right. So, you can imagine some kind of plasma environment around the neutron star, and then something is getting eaten or something is interacting, and it’s just this completely separate – and so, we might not be able to see the regular beams from the thing, but every now and then, something chirps, and then it’s gone.
Dr. Pamela Gay: And it could be – these things aren’t getting labeled as pulsars yet. We don’t have enough data to label them.
Fraser Cain: And they don’t match pulsars.
Dr. Pamela Gay: And they don’t match pulsars at all. So, this could be instead of a pulsar-like mechanism, it could be anything from magnetic fields rearranging themselves to eating asteroids – this is a thing they can do – to perhaps there’s a nearby star that they keep periodically stripping a little bit of material off of, and we get a nice, friendly radio burp. We don’t know. We’re at the cool speculation phase of this.
Fraser Cain: My favorite phase.
Dr. Pamela Gay: But at least we have observables.
Fraser Cain: Yes, of course.
Dr. Pamela Gay: So, I can constrain your parameter space.
Fraser Cain: Okay. So, right now, all we know, really, is that they seem to happen randomly. Do we know if they’re happening inside the galaxy, outside the galaxy?
Dr. Pamela Gay: They appear to be extragalactic. So, there are two reasons to say this. The first is the distribution. If something is galactic, you generally expect it to be primarily in the disk. These are, as near as we can tell, as I said all over the sky. The other thing is there’s some really cool observations that have recently come out with press releases from at least half a dozen universities, I think, of a series of observations with what feels like half a dozen press releases or more associated of a fast radio burst that they are naming 121102 because astronomers name things in uninteresting ways. And these all seem to be bursts from roughly the same object.
Fraser Cain: By the way, that number is the date.
Dr. Pamela Gay: I know it’s the date. We still name things in uninteresting ways.
Fraser Cain: Yeah, yeah, yeah, yeah, yeah. So, FRB 140514 for example was April 14th, 2014. But anyway, please continue. Sorry. Just in case people were wondering. When they’re trying to decipher those cryptic and quixotic FRB names, it’s the date.
Dr. Pamela Gay: It’s true. So, there was a long series of observations of this particular source. And it appears to have gone off 15 different times while being observed, and –
Fraser Cain: It’s a repeater. Like, something that’s repeating. That’s a gift.
Dr. Pamela Gay: And so, here we are. We have one that is going off on a regular basis. We have 400 terabytes of data on this sucker, and it’s across all sorts of different wavelengths, so it spans from four gigahertz to eight gigahertz. And looking at it it gives us a sense of this is an active object. This is – it gives us data. We still don’t know what the heck it is. But one of the things that I love is the justification for how they got this data. Do you know the justification for how they got this data in part?
Fraser Cain: No, no, no, no.
Dr. Pamela Gay: So, one of the theories on the origins of these things is that it’s extraterrestrial communications.
Fraser Cain: Oh, sorry. Yes, I know some of these. And there’s an even cooler thing. But go ahead and talk about your part, and then I’ll talk about an even cooler part.
Dr. Pamela Gay: So, part of the drive to do this and part of the name of the project is they were actually looking to see if they could figure out if this was extraterrestrial origins. So, this is a project called Breakthrough Listen. And I just love the fact that they’re like, “Okay. We’re gonna roll this out, and we’re gonna get amazing data that can be used for science, for the hunt for life, for all these different things.” And the idea behind this project is they looked and looked and looked and looked at a little tiny dwarf galaxy about three billion lightyears away trying to understand what might be in that dwarf galaxy.
Fraser Cain: Breakthrough Listen is involved in SETI in general. They’re providing telescope time, helping fund various scientists to search for signals from extraterrestrial intelligence, and this is one of them. And so, the idea is that maybe aliens are using these FRBs to communicate in some way.
Dr. Pamela Gay: Yes. So, basically, the way to think of it is we have periodically sent out bursts of laser light in order to nominally communicate with aliens out there. And the thought is what if a particularly advanced civilization, instead of sending out bursts of laser light, instead sent out bursts of fast radio signals. Maybe it’s a thing. It could be a thing. It’s as good a theory as any. It just requires a lot more evidence than many of the other theories before someone will believe it. But it’s worth looking into, especially when the data needed to look into that theory is good to also prove and disprove a whole lot of other theories.
So, in this case, one of the things they were able to just prove is that fast radio bursts come from catastrophic events because once, in general, unless you’re Eta Carinae, once you explode something once, you’re not gonna explode it again. And where they’re seeing multiple bursts that appear to be coming from the same place on the sky, that seems to rule out the idea of a catastrophic origin of these things.
Fraser Cain: One of the things that I thought was really neat was in Australia, one of the observatories that they’re using – one of the interesting things about it is that it is far-sighted. So, this instrument can’t detect anything that is within 10,000 kilometers of the Earth.
Dr. Pamela Gay: Why?
Fraser Cain: I don’t know. The way it’s tuned. I don’t know. But the thing that’s really fascinating about it is it was able to detect these fast radio bursts, and what that did was confirmed without a doubt that they’re extraterrestrial in origin. I mean, they could be coming from the moon somehow, but they’re definitely not coming from within 10,000 kilometers of the Earth. And I thought that was really fascinating.
Dr. Pamela Gay: Wait, 10,000 kilometers is – yeah. So, that’s nearby. That would be something moving very fast across the sky, so that means they have a very small field of view. Okay. I now track how that could be possible.
Fraser Cain: Yeah. So, it can’t detect anything that’s within that range. And so, they were able to then essentially, rule out satellites, secret military satellites, pieces of space junk, things like that, which I thought was great.
Dr. Pamela Gay: So, we’re up to the point where we know some of these things repeat themselves. We know they’re scattered all across the sky. We know they’re probably not cataclysmic events. And that’s all we really know. And what’s fascinating is how few of the possibilities of what they are we’ve been able to rule out because if it’s a matter of eating asteroids, well that can repeat if you have a really dense field of debris that you’re happy, dead star is moving through.
You can have repeating of stripping material off of your nearby neighbor star. And we know from recurrent nova that some of these events repeat on a very regular basis. Some repeat on a completely random basis. And some don’t repeat within a human lifetime. So, we still don’t know a lot. And that’s awesome. This is why we do science. And what’s cool is looking over this, it keeps being students and young, early career people that are making all of the breakthroughs because they’re the ones asked to do the boring work. And these quirks just keep showing up in the archives.
Fraser Cain: And one of the things that – we’ve talked about this a bit in the past – that attempting to scan the sky for radio waves is very different than attempting to scan the sky for visible light. We’ve got some pretty amazing telescopes coming shortly. They’re gonna be these all-sky surveys that are scanning the sky every night, that are gathering enormous amounts of data. And you couldn’t imagine even some kind of telescope that’s watching the sky for some bright flash.
And there’s the various gamma ray observatories out there that are scanning the entire sky waiting for a burst. But the problem is that you can’t scan the entire sky very easily in radio emissions. You have to sort of listen spot after spot after spot, right?
Dr. Pamela Gay: Yeah. And you have to trade off resolution for coverage because when you’re doing radio, you’re essentially observing one pixel at a time. And so, you scan across your object. Now, if you have a giant pixel, you can say whether or not there’s an FRB over a long period of time in this one little tiny place, or you can just keep scanning that one place over and over and over and get a much more focused location, but decrease the probability you’re actually going to see something because you’re scanning across a –
Fraser Cain: Yeah because it’s gonna miss that five-millisecond moment when it went off and then never came back. I’ve heard estimates that there could be ten thousand of these a day.
Dr. Pamela Gay: Yes. That’s some of the calculations.
Fraser Cain: Dozens have been detected to date. It’s amazing to think that there could be ten thousand, and that just shows you how little of the sky we’re watching in radio waves on a regular basis. And this shows you the challenge of things like SETI. To search for signals from extraterrestrial intelligence, you’ve got to point at one place, tune to the right frequency, listen, point to a different place, tune the frequency.
So, let’s talk about some upcoming instruments that are gonna try and take this step further. And as I was mentioning, the sweet halfpipe is there’s an instrument that has been built called CHIME. Yeah. And it is here in British Columbia. It’s in the Kootenays. I really wanna go and check out the facility at some point. And it looks like a bunch of skateboard halfpipes.
Dr. Pamela Gay: It really does.
Fraser Cain: It does. Yeah. Bolted together. I think it’s three maybe or four. And it is like the perfect machine for finding FRBs. So, it stands for the Canadian Hydrogen Intensity Mapping Experiment. And so, it has other jobs.
Dr. Pamela Gay: This is a big Canadian collaboration between University of British Columbia, McGill, University of Toronto, and International Radio Council, and the Dominion Radio Astronomy Observatory. It had its first light in September. It’s up and operating. And when they were building it the goal was to be studying the expansion of the universe, trying to understand dark energy, trying to constrain our Lambda Cold Dark Matter models.
But it turns out the kind of data that they’re getting in order to understand all of these other different things have the potential to turn up basically, thousands and thousands of these fast radio bursts if they are as common as we believe they are. What’s interesting is they also hope to use it to detect the kinds of things that generate gravitational waves. These are the neutron, neutron star collisions like were observed back in August. So, here we essentially designed to do only the most cutting edge of science involving weird stuff we know almost nothing about and how our universe is expanding.
Fraser Cain: Yeah. And specifically, it’s tuned to the 21-centimeter radio wave, which is what’s emitted by neutral hydrogen.
Dr. Pamela Gay: And it’s tuned to observe them redshifted so that it’s observing the most distant clouds. So, they’ve adjusted the wavelength so that it’s that redshifted 21 centimeter that they’re observing.
Fraser Cain: And this is one of this mysterious times of the universe, wondering how those first clouds of hydrogen came together to form the first stars. Did they collapse directly into black holes? Did they turn into stars, and then the stars merged into black holes? It’s a really mysterious time. And I mean, James Webb is gonna help us get to the bottom of it, but it’s nice to know that we don’t have to necessarily wait for a super, duper space telescope to start getting some answers.
Dr. Pamela Gay: And what’s kind of amazing to me is this particular telescope, it’s not exactly steerable, you might say. And it’s only gonna map three percent of the sky. But three percent of the sky is all we need when you consider the increase in volume that can be seen at larger and larger distances. And so, it’s going to do a fairly complete sample of this cone through the volume of observable universe. And that’s going to help us answer all of these different questions.
And this is very much the same strategy where Kepler is looking at a single field and getting us all the information on planets in this one cone in the sky. It’s the starting point for the Sloan Digital Sky Survey that looked at initially one place on the sky and measured that cone. And over time, all these cones start to give us a statistically useful amount of information where we take what we saw on the cone and then multiply it out over the rest of the sky to figure out what should be observed everywhere else.
Fraser Cain: We’ve mentioned this a bit before when we talked about some of the other instruments and surveys and stuff that are coming out. But I think we really feel like we’re entering this next revolution of time-based astronomy where we’re not just looking at things in ever greater resolution and detail, but we’re shifting towards seeing what the sky is doing when we’re not looking.
And the large synoptic survey telescope is gonna be the best example of this, but you can imagine this future when we’re watching a goodly portion of the entire sky across many different wavelengths and just getting a sense of how active and unusual things are. Before we wrap up the show, I gotta throw in the craziest speculation for what this could be.
Dr. Pamela Gay: Crazier than aliens?
Fraser Cain: Well, it’s aliens, but it’s crazier than aliens. It’s crazy aliens. Craliens. So, one of the ideas is that – and I think the astrophysicist Avi Loeb did the calculation, but I’m not entirely sure. But he sort of has his hands in everything. So, one of the ideas is that it is a gigantic spaceship propulsion system. And so, we’ve talked about this in the past that seems to be one of the most effective ways to send spacecraft from world to world is to use a laser. And you zap your spacecraft with the laser, and then that propels the spaceship to head off to its other destination.
This is what the Breakthrough Starshot is gonna be. And so, they did the calculations and found that if you could release some significant portion of the amount of energy that, for example, the Earth receives every year in this gigantic laser pulse, you could emit at this huge redshifted distance that kind of radiation for that frequency for that length of time and that it would be enough to send a fairly significant spaceship on a fast journey to another star, which I love. Of course, it’s not that. But still, it’s cool.
Dr. Pamela Gay: Yeah. And we’re dealing with redshifted light, so it’s awesome.
Fraser Cain: Yeah. So, we’re seeing something that is billions of lightyears away, but it has been redshifted from whatever laser beam they’re using to the radio spectrum. So, I –
Dr. Pamela Gay: Now, does that explain the polarization and everything that’s being seen?
Fraser Cain: Well, that’s the thing is that some of these things are now seeing the kind of polarization that perfectly matches what you would see in a highly magnetic environment, as you mentioned. So, it really feels like now, what you mentioned. A neutron star is gobbling up an asteroid. It’s creating this release of energy that’s being funneled through the highly magnetic environment, and you’re seeing this zap. But again, more data necessary.
Dr. Pamela Gay: It’s true. And we’re working to get it with CHIME, with collaborations of so many of the different radio telescopes across the world: Green Bank, Arecibo, the folks down in Australia with all their different radio telescopes. This is an amazing new thing to chase down. And annoying because it’s so brief.
Fraser Cain: And I feel like we’re going to be able to come back to you – this is one of them that I feel like we can come back to you in five years and say, “We pretty much know what FRBs now.” And when we do, we’ll give you that follow-up episode. But this is the, “Here’s a crazy mystery. We don’t know what it is –
Dr. Pamela Gay: But we have observables.
Fraser Cain: But we have observables.” Have fun. Enjoy the mystery. Thanks Pamela.
Dr. Pamela Gay: Thank you, Fraser.
Male Speaker 1: Thank you for listening to Astronomy Cast, a nonprofit resource provided by Astrosphere New Media Association, Fraser Cain, and Dr. Pamela Gay. You can find show notes and transcripts for every episode on astronomycast.com. You can email us at info@astronomycast.com, tweet us @astronomycast, like us on Facebook, or circle us on Google+. We record our show live on YouTube every Friday at 1:30 p.m. Pacific, 4:30 p.m. Eastern, or 2030 GMT.
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Duration: 31 minutes

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