The Supermassive Podcast - 12: Gamma Rays & Christmas Stars

Episode Date: December 18, 2020

This month, Izzie & Becky are taking astronomy to the extremes with gamma ray expert, Professor Paula Chadwick, and Professor Julian Osborne from the SWIFT Observatory. Plus, Robert Massey shares his top tips for stargazing at home and how best to see the conjunction of Jupiter and Saturn on December 21st. Send your pictures and questions to [e-mail] or tweet @RoyalAstroSoc using #RASSupermassive. The Supermassive Podcast is a Boffin Media Production by Izzie Clarke and Richard Hollingham

It's literally the universe's best firework show. They're the biggest bang since the Big Bang. Just as a hypermarket is bigger than a supermarket, so a hypernova is bigger than a supernova. I think high energy physicists are the Indiana Jones of astronomy. Hello, welcome to the Supermassive podcast from the Royal Astronomical Society. With me, science journalist Izzy Clark and astrophysicist Dr. Becky Smethurst. Yeah, this month we're ramping up the energy with my favourites, gamma ray bursts

and high energy physics. I mean, we really are taking astronomy to the extremes with this topic. I mean, literally, yeah, like the gamma ray bursts, gamma rays, it's the extremes of the electromagnetic spectrum, right? So to get things like that, gamma rays, X x-rays you have to have your extreme astronomical objects as well you know the stuff that's I think it's the best I remember doing an extreme astrophysics module at university

and you come out of the lectures like oh my goodness my mind is blown I need a cup of tea and a sit down yeah definitely a little bit dumbstruck. And with us, as usual, is Robert Massey, Deputy Director of the Royal Astronomical Society. So, Robert, when it comes to gamma rays and X-rays, we stop talking about wavelengths and frequencies and everything is just described in energy. That's right. It's, you know, astronomy is famous for having eccentric units that only mean a lot to astronomers. This is no exception. So, well, this one is particle physicists as well, but electron volts and kilo electron volts and mega electron volts are the kind of preferred units. And they describe the way that an electron is accelerated by an electric field by a voltage. So that's what we use. You talk about the kind of energy that these particles, the gamma rays, the X-rays can have, and some of them are really, really stonkingly high. So that's what we use. You talk about the kind of energy that these particles, the gamma rays the X-rays can have,

and some of them are really, really stonkingly high. So that's why we use that. It doesn't make any sense anymore to talk about the sort of wavelengths that you're familiar with with optics, because actually it's also really, really hard to treat these optically. There are really exotic X-ray telescopes that focus things, but generally it's a completely different type of astronomy. Cheers, Robert. We'll catch up with you later in the show then

for some proper optical stargazing rather than anything through the X-rays and gamma rays. We've spoken about the electromagnetic spectrum a fair bit recently. We're used to radio waves, which, as we discovered last month, are quite low in energy. And on the other end of the spectrum,

there are X-rays and gamma rays, which are high in energy and on the other end of the spectrum there are x-rays and gamma rays which are high in energy. So gamma rays are up to a billion times more energetic than visible light and are used to understand these extreme events in our universe. I spoke with Professor Paula Chadwick from Durham University who explained where in space these gamma rays come from? They come from anywhere that has big, strong shocks in, really strong magnetic fields, all these kinds of things. So what we're looking at are things like jets coming out from black holes. We're looking at the remains of supernovae explosions.

We are looking at rapidly rotating neutron stars, the pulsars, all these sorts of places where anything extreme is happening is where the gamma rays come from. I mean, yeah, that all sounds as extreme as it gets. Pretty much. What is it about all of these different extreme astronomical objects that means that they release gamma rays? How does it work? So what's happening in these objects is that they are accelerating particles to very high energies. These are typically things like electrons, but they can be protons,

which are basically just hydrogen nuclei, and maybe even heavier things than that as well. They're being accelerated to very extreme energies by things like supernova shock waves. Any time you take a particle, a charged particle, and you accelerate it, you will end up producing some electromagnetic radiation. And because these things are really energetic, we get to produce gamma rays. So how are you trying to detect all of this?

Well, the good thing at one level for humanity in general is that gamma rays don't get through the Earth's atmosphere. So that's great. If you're an astronomer who's interested in gamma rays, this is a bit of a pain. So the obvious thing to do is to get a telescope above the atmosphere. Many gamma ray telescopes exist and have existed that do that. Many gamma ray telescopes exist and have existed that do that. The most prominent one, I guess, at the moment is something called Fermi, which is a NASA satellite, and that sits above the atmosphere. And this is fine, but the whole of gamma rays actually covers a really huge range in terms of energy.

And as you get to higher and higher energies, there are fewer and fewer of them because you need a more and more extreme process, as you can imagine. So consequently, what we really need is a very big area of our detector in order to be able to detect these really energetic gamma rays. If you wanted a satellite to do this, then your satellite would need to be the size of about two football pitches, which is going to be kind of hard to launch. So what we do actually is we can use the atmosphere as our detector once we get to these really energetic gamma rays. So what happens is this, a gamma ray comes into our upper atmosphere, it interacts with the stuff in our upper atmosphere, the nuclei of the nitrogen and things like that. When it does that, it creates more particles and it creates, in particular, electron-positron pairs. So electrons and their positively charged twins. Now because the gamma

rays had an enormous amount of energy, the electrons and positrons are moving really quickly. In fact, they're moving faster than the speed of light in air. So light is actually travelling a bit slower in the atmosphere than it would in the vacuum. When that happens, when we get a charged particle going faster than the speed of light in air, we get the light speed equivalent of a sonic boom. Right. It's called Cherenkov radiation. It's blue and it doesn't last for very long in the sky. It lasts for a matter of a few billionths of a second and it's very faint. It's only one ten thousandth of the total starlight, but we can detect it.

Gosh, you've got to be very quick to sort of spot this. It's obvious that this is exploring the extreme ends of our universe. I mean, neutron stars, remnants of a supernova. But there's another term that I've heard before, which is a gamma ray burst. So what's that exactly? And is that different from what you're studying here? have had actually ground-based telescopes detect gamma-ray bursts. We don't see very many of them for reasons that are going to become clear in a second. So gamma-ray bursts are fascinating things. They're extremely bright explosions in the universe. They come in two kinds, they're short and long. The short ones last a matter of seconds and these come from the in-spiral of two neutron stars. So two neutron stars are going around each other. They get closer and closer and closer and closer. And eventually they collide with each other. And we get a short burst of gamma rays from that. And we also get gravitational waves,

I should say. And then the long burst, which lasts for tens, hundreds of seconds. These come from things that we've dubbed hypernova explosions um just as a hypermarket is bigger than a supermarket so a hypernova is bigger than a supernova oh my goodness and they seem to contain um emission that is strongly jetted towards us so somehow the emission is being focused if you like in in a particular direction so if you're close enough to one of those then um we have a problem happily there's nothing that looks like it's going to produce anything like a gamma ray burst anywhere near us so we're not going to be wiped out by them anytime soon no no you're not going to be wiped out by them anytime soon okay so for you you know what's next for this field what really

excites you for the future of gamma ray astronomy At the moment, those of us who work at these really high energies are focused on building something called the Cherenkov Telescope Array, or CTA for short. Like most of astronomy, we're very keen on the three-letter acronym. So CTA will consist of two arrays of telescopes, one in the northern hemisphere and one in the southern hemisphere. That will give us full sky coverage. It will be at least a factor of 10 more sensitive than anything we've built before. And at the really extreme energies, it will be able to explore this region in a way that nobody's ever been able to do before at all. We're expecting it to increase our catalogue of known extreme sources

by a factor of something like 10. And that will really help us because we think at the moment, with our current telescopes, we're looking at kind of tips of a lot of icebergs. You know, we can see a few objects that are really, really bright of lots of different classes. So lots of these black holes with jets and things like that. We have a feeling there should be many, many more. And we just need a more sensitive telescope to see a bit more of the iceberg so that's really exciting and also with these telescopes we can do what i sometimes call

weird physics certainly certainly going beyond the standard model of physics so looking at things like is it really the case that the speed of light in a vacuum is the same for photons of every single energy? There are some theories of quantum gravity that suggest that may not be the case. We can also hunt for dark matter at energies that something like the Large Hadron Collider simply cannot do because it can't get particles to sufficiently high energy. So those things are really interesting to us. That was Professor Paula Chadwick from Durham University. I think high energy physicists are the Indiana Jones of astronomy. I swear, like everything is just so extreme. It's ridiculous. You know what, if anybody could be labeled the Indiana Jones of astronomy, it's Paula or Professor

Chadwick. And she'll always be known to me because she actually taught me when I was a student up in Durham as well she taught me the high energy astrophysics course you were talking about before Izzy and like it's no wonder I ended up working with like black holes and high energy stuff because she's just well she's just captivating right she makes it so interesting I mean it is interesting but she just she just takes it to another level I reckon absolutely and I love how she just casually dropped in the term hypernova i mean i need more information on this becky what exactly is that there's no real threshold for it as in you know you cross some threshold from supernova to hypernova or whatever but we do sort of classify them as the very energetic supernova so the one thing i love about supernova physicists is they invented their own unit, which of course they did. So most supernova are measured in terms of energy around about the 10 to the 51 ergs, right? So that's a one with 51 zeros after it, which is a very old sort of unit of energy.

of unit of energy and so the the unit they invented for supernova is foe or a foe which is 51 ergs like 10 to the 51 ergs so they'll be like oh that supernova is like you know like two foe or like four foe or whatever but a hypernova is like 10 to the 52 ergs right they're an order of magnitude more energetic and they come from very weird and wonderful stars maybe stars that are maybe spinning very quickly or perhaps they have sort of um very different cores kind of thing that put them very sort of dense and stuff like that we don't really necessarily understand and pinpoint them specifically but every time there is a new one we learn a little bit more and what i find interesting about this whole field is that we stop using traditional telescopes, if you like, you know, there's that crossover of particle physics and astronomy. Yeah, a little bit like Paul was saying, you know, the reason that we can detect these gamma rays on the ground is because of these sort of particle

creation events that happen in our atmosphere. And so it's very similar to what they do in sort of the big particle detectors of, you know, the LHC at CERN with the ATLAS detector, these big sort of particle accelerators that collide particles together. And then the way they detect what comes out is sort of from the fallout, you know, and that includes gamma rays that are often given out as well. So there is a real parallel to what particle physicists are doing, which is why I love that it then ties back in, as Paula was saying, to maybe, you know, figuring out what dark matter is made of as well. There is the very sort of close connections between gamma ray astronomy and particle physics, and it's not necessarily something you would have put together. Yeah, absolutely. Now, I actually just want to pause on the high energy physics for a moment, because safe to say, I am well into the festive spirit the tree is up I've made 36 minutes by and eaten quite a few of them already I'm already wearing my Christmas jumper to record

this yeah we're very festive we're there and so I thought we could mix things up a bit with some festive astronomy so Robert in the Christmas story it says that there was a star shining over Bethlehem but astrophysically speaking, could there be an explanation for that? No, there absolutely could, because the Christmas star, the star of Bethlehem, covers such a multitude of things. There are any number of explanations. So people have wondered about this for a very, very long time. There's the sort of, you know, the grumpy theory that actually there was no star of Bethlehem. And it's just what's described as a pious legend or pious lie or a midrash

where they just add an embellishment. If it was something, and it's completely uncertain, we'll probably never know for sure, then it could be things like two planets close together in the sky. Actually, like we'll have coming up this month, Jupiter and Venus were close together in 3 and 2 BC. Jupiter and Regulus were close together around and 2 BC. Jupiter and Regulus were close together around the same time, the star Regulus. There was also a triple conjunction

where Saturn and Jupiter moved together in the sky and were close-ish together three times. And bearing in mind, I guess, that you'd probably be talking about an astrological explanation, you know, people looking at these things and wondering what they signified. Now, Jupiter and Saturn being moderately close together is not super spectacular, but I can well imagine someone looking and saying, oh, that's a weird set of events. There also might have been a comet, you know, that just isn't recorded that well, wouldn't necessarily have to be that bright. Or it could just possibly have been a nova, probably not a very bright supernova,

because there would be more records of those. But it is just possible that there really was a new star that was around for a while. But I honestly think we'll never know for sure. And it could be any number of things. Yeah, I've read into this a couple of times as well, Izzy, because I think it is quite fascinating to think if there is some sort of science grounded in these sort of like legends in a way.

And one thing that always stuck with me is the word that's used sort of in the traditional text is magi i think i'm pronouncing that right right to describe what we call the wise men but that's people have sort of now said that's a bit of a mistranslation because in the context that it was used magi probably actually meant astronomer or astrologer as robert was saying right so they probably did read into some event that they were seeing and i love sort of seeing theologians trying to sort of say well maybe they thought this but maybe they didn't and the cultural things that tie into it so for

example robert mentioned comets and a comet really would look as if it was sort of hanging over a city in a sky and that could really sort of you know lead people to sort of following it in that direction south from jerusalem to bethlehem but comets were also seen as really bad omens so they think well actually culturally they probably wouldn't have followed a comet because they would have been like oh don't go over there you know yeah exactly and I just it is really fascinating to think about it like there was a couple of supernova recordings sort of in China and Korea back in sort of like 4 BC as well so there are a couple of things you could pick out but because we can we can literally track the sky back we know the movements of the stars and the planets and everything so you can

do this very precisely it's just no one really knows like the day this happened either we're tying it to sort of events around it like the death of Herod and stuff like that which are recorded so it's a little bit difficult but it is fascinating isn't it Robert to think about it yeah I mean and I think I think that's the thing you know it's really the forensic astronomy if you like in this context is hard because although we know the positions the planets you know if there was a moderately bright comet that doesn't we don't have good records of we'll never be able to track it back and you know the same with some I think at least novae rather than supernovae you know if they were if they weren't so bright that they were recorded in a lot of texts it's really difficult to pin it. And as you say, the date of the birth of Jesus is uncertain.

So, you know, I think you can really pick what you like. But the comet is a nice idea. I mean, I can definitely imagine a bright comet like we had near-wise this year. If you imagine that hanging over a direction in the sky. Now, I mean, I suppose the slight flaw in the plan is that as the night goes on, the comet moves from one bit of the sky to the other. So you don't have a direction in that sense. But yeah, I can see that being very symbolic. I mean, imagine people depict comets as hanging swords in the sky

and all those kind of things. However, as you say, they're not always good omens. So they signify change, you know. So yeah, who knows? And the other thing we've got is like confirmation bias in there as well. you mentioned all those conjunctions robert i was reading about this that the one big leading theory is like there was a conjunction of jupiter and regulus in like september 3 bc which they sort of like oh that's nice but then nine months later there was a conjunction of like jupiter and venus and so they might have read into that as being like a king born under a house

and then because jup Jupiter was then continuing its motion across the sky it actually probably had gone into retrograde apparently and they worked out that by December 25th in 2 BC that was when Jupiter's retrograde motion stopped and turned around and so it will have hung around in the sky for a long time sort of in a similar looking place and so that and it's sort of like oh but just because it happened on december 25th like we don't know if you know that december 25th could be an arbitrary date picked in the middle of hanukkah it could be something to do with the old sort of like um solstice traditions on the 21st you know and it's sort of this confirmation bias that we're almost like looking for something you know and it's sort of a weird one isn't it i agree no and i think i mean it's sort of a weird one, isn't it? I agree, though. And I think, I mean, it's not just the date. We don't know the year.

Yeah. It's really hard to get a handle on it. I think what is nice is I suppose that it's nice to think that there is some bright event in the sky that people regard that as special in some sense. And they probably, you know, they attribute a lot more to it than we would these days. probably you know they attribute a lot more to it than we would these days but you know i can i imagine looking at the way which will come on to later on jupiter and saturn are getting closer into the sky i can well imagine people would see some significance in that i think it's really interesting there that we have the ability to track back the skies and see what what was positioned where but then we're also backing that up with any documents that we can

find from a similar time yeah i've heard this called like astronomical archaeology almost before like historical astronomy it's a weird one but i like it yeah and so is is that done quite a lot do we think or is that just purely because you know we have christmas every year it's quite a popular story or is there more is that a field in its own potentially? Yeah, I mean, particularly, well, there's one good example, which is people use things like observations of total eclipses to pinpoint the track of the eclipse over the Earth's surface and then deduce the long-term change in the rotation of the Earth.

That's a very serious field. People do it with things like trying to look at, say, Stonehenge as an eclipse predictor, or I guess also associating appearances of things like comets in the sky with events. So the Battle of Hastings and Halley's Comet, for example, a couple of years earlier, that's another association. So, yeah, I think people do it. With planets, it's not too hard to do, at least for a few thousand years either way. But even after that, you start to struggle. The errors in even the really accurate determinations

of the planets around the sun, small positions, errors in position start to build up. So it does get more complicated the longer you go. But you know what makes me laugh is that people don't realise we can do this, like that we can actually, given any date, you know, we can tell you what the sky looked like on that date and so one thing that always used to annoy me they fixed it now is in the original titanic film you know how they went to such lengths to make everything

super historically accurate and like the the effects were incredible when she's lying on the the door at the end in the ocean and she's looking up at the sky they were just like okay so just a random scattering of lights will do and like the amount of astronomers were like we knew the exact date and we knew exactly what the sky looked like and so when they re um you know they refinished it for release a couple years ago they they fixed it and all the astronomers in the world went thank god i'm now now determined to look at those scenes to check well from, from Titanic to the Christmas star, that's something to share around the table this Christmas. Now, as we heard earlier, gamma ray bursts are the most powerful explosions the universe has

seen since the Big Bang. But they remain a bit of a mystery and they happen so quickly that you need a pretty speedy telescope to spot them. And so in November 2004, NASA launched the Swift Observatory to track these events. Now we're joined by Professor Julian Osborne, who leads the Swift effort at the University of Leicester. So Julian, it's Swift by name. Is it Swift by nature as well? Absolutely. Most satellite observatories manoeuvre from one pointing to another very slowly, maybe an hour or more. SWIFT is not an acronym, it's just very fast. Typically it can repoint within a minute or two and that's vital for the science that we need to do. So Julian, what actually happens when a gamma ray burst goes off? Swift has a wide field

telescope called the Burst Alert Telescope, the BAT. And this BAT can see about one sixth of the sky at any time. And so if a gamma ray burst goes off in that part of the sky, then the bat will detect it and it will tell the spacecraft, please move to point in that direction. And the spacecraft then checks that it's safe to do so and rushes off to do that. What are you actually detecting and looking for? After the spacecraft has slewed, when the bat has detected a gamma-ray burst,

it then points its other two telescopes at the burst. So it's got an X-ray telescope and a UV optical telescope, and we're studying the burst in the X-ray and UV optical wave bands. Usually, by the time that Swift has got there, we're looking at the results of the collision of the ejection from this burst with the surrounding medium. A huge explosion occurs on the gamma ray burst. Material is flung out at super relativistic speeds and it slams into the surrounding gas, causes that to be very highly energised and to emit over many different wavelengths, including X-rays and the optical. And that's really what we're looking for.

We're trying to understand the physics of the bursts themselves and the physics of the effect they have on their environments. What can we hope to learn from gamma-ray bursts? Gamma-ray bursts are extraordinarily bright. They're the biggest bang since the Big Bang, and that means that we can see them as far back and as far away as they exist. So if the very first generation of stars, if one of those stars was to explode and make a gamma-ray burst, we would be able to see it.

In fact, we may already have seen it and just not recognised it for what it is because, unfortunately, we don't know the distance to many gamma ray bursts that we find. We do already have, for example, a gamma ray burst which was detected when the universe was about 4% of its current age, so the universe was very different then. And that very bright explosion, all the light from that has to pass all the way from that great distance to us and of course it's passing through all the material in between us including the galaxy that hosted the gamma ray burst when the universe was that young the galaxies were very different to how they are now

and so we can use gamma ray bursts to x-ray early universe galaxies for example and look at how the abundance of the elements was different in those far distant times for example so we can look at the growth of the elements in the universe it's fascinating that you can do that with gamma ray bursts as well though it's just incredible. So Julian with sort of everything that we've learned since first light in the mid-2000s when Swift was first launched it obviously had certain objectives in mind did it does it have the same objectives still to this day with everything we've learned or has that sort of changed? Swift has continued to evolve we've've observed well over 1,000 gamma-ray bursts now.

We discovered all sorts of strange things, but the design of the spacecraft required to react very quickly to these gamma-ray bursts, which fade so quickly, meant that it was a very agile spacecraft. And so we have huge demand for so-called target of opportunity observations now and in fact swift spends most of its time just reacting to astronomers saying oh please let's look at this oh please let's look at that and it does it tens of times a day so one of the i have

done it julian one of the reasons that i didn't become a gamma ray astronomer and didn't want to study gamma ray bursts is because when I was an undergrad I found out that if you get one of these alerts that something has been detected by something like swift you know it's sort of drop everything you know whether you're at you know at the middle of the night or whether your cousin's birthday party or something and you just have to follow up immediately is it still like that or is it more remote these days especially with a space telescope it was it was extremely exciting in the early days i can i can assure you um you know people did have to jump out of bed and get to their computer you know they went off when people were in the shower you know you have to

jump out so people were on duty for for some hours um and if a burst went off then you know they're that we get the data very quickly within a few seconds and your phone goes off and you have to react fortunately we've now managed to automate many of our procedures certainly for the x-ray telescope the analysis is sufficiently well understood that we've been able to almost completely automate it so people are getting their beauty sleep a bit better now i'm so glad to hear that and i almost i'm so sad for myself now i'm like look what you deprived yourself of because you didn't want to get up in the middle of the night i have one well it was it was very very exciting i mean when you've got a new facility like that everyone's enthusiastic for good reason you know we were having seminars in

the corridors just because new stuff was happening all the time and saying what could that possibly mean and you know it was it was terrific really exciting thank you so much julian for joining us there i can't believe that you didn't make a single taylor swiffer i literally was just like sat there sat on my hands is he like don't don't say it don't say it don't say it don't say it I was watching you like she's gonna say it she's gonna say it it was the biggest effort I've expended this year um anyone that doesn't know Becky is a huge Taylor Swift fan huge so happy right now double album in a single year but now I've actually been in a talk from someone

before um another like a fellow PhD student back when I was a student who was working with Swift data and I think they were as big a fan as I was and on every slide there was a Taylor Swift gif like reacting to the science like on the slide and I still remember it to this day I'm like it's the best talk I've ever been to it was like a talk that was specifically written for me. This is the Supermassive podcast from the Royal Astronomical Society with me, astrophysicist Dr Becky Smethurst and with science journalist Izzy Clark. This month we're taking things to the extreme with high energy physics. Now before we get into everyone's questions, I think it's my duty to let you all know that not only can you see your loved ones this Christmas but you could also see Becky on Christmas

University Challenge. Honestly I got the call and they were like do you want to do it and I was like yes I want to do it. I couldn't say yes quick enough it was an absolute dream come true seriously. Like it's like supposed to be like celebrity alumni. And I'm like, am I close to a celebrity? Because I don't think I'm close to a celebrity. But honestly, those lights hit you and you hear the music in the studio and you forget everything you've ever known ever. And it's terrifying. The buzzers are so loud.

Honestly, I jump every time someone presses it. If you watch the show, you'll just see me going jumping I literally couldn't think of anything that is more stressful yeah you mean you're like I love it I want to do it I feel I would really have to think about that if I got the call I love watching it it's a thing in our house that you know we watch it we have our fingers on the pause button ready to like try and match the answers it's a big thing um but actually doing it I don't know I don't know if I could cope that is that's the moment where all you can remember is like the useless information of like who you met in the park five years ago like well luckily my yeah my my my my bank of useless information was probably more

useful to me than all of the loaded education I've ever had. One thing you might like to know, Izzy, is that Jeremy Paxman wears a leopard print face mask. Oh, my goodness. That is absolutely the information that I needed. Oh, my God. Did you get a photo? I didn't, no.

I got a photo of our team, which was great, but I didn't get a photo with Jeremy because I was every social distancing and all that but I had a really great chat with Robert with Roger Tilling who pronounced my name right as well I was like you're a god amongst men I would probably have that set as my ringtone if someone like rang so who else was on your team uh there was um ed gamble was on my team who is comedian uh hugh pierman who is the uh sort of like an architectural digest uh critic sort of like from the river house of the year that kind of stuff and then also sarah keith lucas who is uh the weather person

on bbc news as well and every time she comes on in our house now my my partner is like ah best friend sarah so when can we see you in all of your wonder uh the 28th of december bbc2 half past eight oh my goodness i cannot wait well we don't have questions from jeremy paxman but we do have some from our listeners for you and for robert and you may confer so becky kaz on twitter asks what's a magnetar and what causes it yeah um so magnetar is a special type of neutron star it has an incredibly high magnetic field hence magnetar um and i'm talking like a billion to a hundred billion tesla that's the unit of magnetic fields and that's um billions times trillions even times stronger than the earth's magnetic field so this is an incredibly high energy object like what we've been talking about right and we think that the decay of that magnetic field so it starts off very high and

over about 10 000 years or so it decays back to nothing so it's very quick in terms of like astronomical time scales right yeah young yeah exactly it's like a blink of an eye yeah and so in that sort of decay process we think that's what gives out gamma ray bursts maybe even some fast radio bursts as well might come from magnetars and they do sort of rotate slower than neutron stars and like pulsars as well which are very special type of neutron star which are like they you have periods of like a millisecond whereas magnetars are more sort of like two to 10 seconds. So they're sort of slow in life, but very quick to die off again, I guess as well. And they are, again, some of these such exotic objects

that we don't necessarily understand them as well as we would like, especially because it is to do with magnetic fields and that's the long running joke in astrophysics, right? They know what I understand is magnetic fields. And so do you think all of that magnetism could be due to its makeup or do we still just not know yeah so i mean the leading theory is that there is what we call a dynamo in the center and we've talked about

dynamos before in terms of like the earth for example in the fact that's how it gets its magnetic field right it has um sort of like moving liquid core, which is ionized as well. So you've got electrons separate from protons. So it's charged. If you have moving charges, you get a magnetic field. So it's similar in that respect. And we think there is this very high powered dynamo in the center of this neutron star, this magnetar.

But where it got that from is sort of still a bit of a mystery. Did it develop it once it became a neutron star because of the high pressures and densities? Or did it perhaps come from a star that already had quite a hermetic field because it had sort of got this souped up dynamo in the center as well? There's sort of a little, the jury's still out on it a little bit. From, you know, hypernovas, magnetars, I'm loving it. And Robert, the Duke of Mashupa on Twitter asks, is it true that a single quasar may be as heavy as a billion suns combined?

So remind us, Robert, what is a quasar? Yeah, a quasar is a very, well, typically anyway, very, very distant object where we think they result from black holes in the center of galaxies. So supermassive black holes, which chimes nicely with our podcast. A lot of matter crammed into a very, very small volume of space. a lot of matter crammed into a very, very small volume of space. And because they have stuff around them, falling in, crashing around in them, that releases a lot of energy.

And that's how we see them, because the amount of energy and light released is so astonishing. I mean, they're absolutely extraordinarily bright. We see them right back almost at the beginning of the universe, as far as we can look anyway. And so, yes, it is absolutely true that they can have this vast amount of matter packed into a very small volume we think that most of them are associated with black holes there was a debate about that years ago i think that's pretty much gone now and people associate them with these big big black holes in the center of galaxies yeah this is my baby you

know i'm very glad becky's taking so i I was also particularly glad not having to explain magnetars, which I think is pretty well. But yeah, quasars, I mean, first of all, best word in astronomy, quasar. It comes in second as a blazar, which is a special type of quasar, which we see sort of like face on. So it's like sort of pointing at us.

I always explain to people that quasars, you know, supermassive black holes, people think of them as these objects that are just like hoovers of light right that are dark and we never see quasars are some of the brightest objects in the universe you know and and they're powered by supermassive black holes and it's such an odd thing for people to wrap their head around in the fact that the matter falling in yeah okay once it's fallen in past that event horizon you'll never get any light from it but before it does it's literally the universe's best firework show essentially but it's a firework show of like x-rays and sometimes gamma rays and also radio waves and stuff like that as well so you know it

ties in with the high energy stuff that we've been doing you know and when when julian was talking before about swift being used to study uh quasars you know this is this is why because we want to see the x-rays coming from this light that's spiraling around the black hole. Well, thank you both. And if you want to send in a question for us for a future episode, then email podcast at ras.ac.uk or tweet at Royal Astro Sock. So Robert, what can we see in the night sky this month? I have got a reminder in my diary for the 21st of December. Yeah, that is the event that's going in a lot of people's diaries but a lot of publicity around it because it's being connected to a kind of star of bethlehem of our own time a christmas event

so what's happening on the 21st is that jupiter and saturn that will appear incredibly close in the sky now they'll be 0.1 degrees apart which is uh you know about five times if you imagine the full moon it's about fifth of that diameter so really quite close you should still be able to see them separately with your eye but they are so close that if you take a small telescope you will see two obvious planets in the same field of view and that's incredibly rare very unusual event uh the last time they were that close and they were easy to spot together was in 1226 when of course nobody had telescopes uh there was a there was an event in 1961 where they were a bit further apart and then i think in about 2080 there's another example when they're

similarly close together but it is really quite rare indeed so a lot of us are looking forward to seeing that now if you want to spot it j and Saturn now are getting they're moving effectively behind the sun from our perspective as the earth goes around the sun so that means they're only visible after sunset in twilight in December so you need to get out there and once it starts to get even slightly dark once the sun's set have a look over in the southwest and you'll see if you've got a clear sky and you also I should stress need a very good low horizon as well make sure you haven't got any high buildings in the way if you can uh you should see these two bright objects you'll see jupiter first because that's a lot brighter than saturn uh if it's cloudy on the 21st uh then look on the 12th well you can't know if it's going to be cloudy on

the 21st necessarily on the 20th but have a look on the 20th and on the 22nd as well because they'll they'll still be close together as they will be really for the whole for the whole month and also we had a question from Mark Waters in New Zealand who was asking about seeing these things in the southern hemisphere and the answer is that with this one it's an example of whether you will be a bit better in the southern hemisphere because of the angle of the orbits of the sun and the planets around the sky if you're down in the southern hemisphere you should see the same thing you'll see it after sunset in the same way but they'll be a bit higher as the sun sets it'll be easier to pick out you'll see them in a

darker sky i would really love to see images of this i think this should be i'm sure that the talented astrophotographers that listen to this will be you know planning amazing things and we'll like you to see these really unusual images of the two planets together so i'm very much looking forward to it yeah i mean i'm gonna i've already got my my telescopes ready i've even got just like i'm gonna get loads of a floss get some snacks i know it's gonna be fairly early on in the evening isn't it but still might make it into a evening exactly yeah it's gonna it's gonna have set by six o'clock is so if you were planning you know a five o'clock christmas tipple outside whilst observing jupiter and saturn i think that sounds like an excellent plan socially distance event

right you know you if you it's it's probably difficult for people to share a telescope if you're not in your bubble because of infection everything but you should see this with your eye and even if you only have a pair of binoculars you'll see the two points very close together they'll look like little discs you should see the moons of Jupiter so it's not that hard to see stuff and it's true also if you if you hang around and you make a night of it then as the night goes on uh you know it's a good time of year to be looking at the sky the moon will be the crescent moon will be around. Later on, you'll see Orion, all those beautiful winter constellations that follow. So it's not just about these two objects.

And I really want to stress as well, if you don't see it on the 21st, don't lose hope. Look on the following nights because they'll still be really close together. Yeah, because also I think the more fascinating thing in a way is actually just watching them every clear night you do get, spotting them and noticing after a couple of days how much closer they are together because I mean I've noticed it over November even

the fact that they've gotten that much closer and then into the start of December you can see them getting ever closer again so it's almost going to be more fun sort of in the days running up to it and then the days after it as well watching them get further further apart again and just noticing that is I think is really sort of grounding a little bit almost it's kind of like oh yeah the literal the motions of the planets you know and it's it's noticing it is it's just really awe-inspiring yeah because I noticed that on Tim Peake's Instagram he he posted a photo of you know how far apart they are over the months and how close together and it it forms this lovely V shape.

So I just think it's such an interesting way of, as you say, how you can track it and then see where else it's going to go. And talking of the night skies in December, it's true that Orion has been amazing this month. Every evening, whenever I spot it, you're just like, oh, hiya, there you are. It's such a good time to see it. It's absolutely beautiful. It's a wonderful object. I mean, you know, it was a bit, let's face it,

a slightly challenging year. Actually being able to go out and see something like that is really grounding too. And if you have, you know, you don't need much to appreciate. It's a bright constellation. If you're lucky enough to live in a dark place, it's spectacular. The stars are just simply so bright.

But if you have a pair of binoculars and you sweep around that area, you know, you see the Orion Nebula, you can see the the winter Milky Way you can see all these wonderful clusters so absolutely a good time to be doing it it's not too late at night either now but by 10 o'clock it's getting pretty high in the sky yeah I always say if people are like beginners to this or perhaps they've asked for stuff for Christmas because they've just got into it for this year like binoculars a telescope Orion is just the best place to start because a it's so easily recognizable so you can spot it so easily in the sky that you're like right okay i'm good i know where i'm going and then b also there's just so much to see around

there so you thought the orion nebula robert but also one thing i love there's a christmas tree cluster really close to orion as well because it actually does look like a christmas tree it's like a triangle shape and it's sort of the very two top stars in Orion, Betelgeuse and Bellatrix, sort of above Orion's belt. One's blue, that's Bellatrix on the right hand side, and then Betelgeuse on the left hand side. If you sort of draw a line between the two of them and follow it the same distance again, sort of to the left of Orion, that's about where the Christmas tree cluster is. So if you get something like binoculars for Christmas, see if you can find the Christmas tree cluster, because that's such a Christmassy thing to do. so if you get something like binoculars for christmas see if you can find the christmas tree cluster because then that's such a christmasy thing to do and if you do see it you know tweet us if you're trying some of this astronomy at home either for the first time or for the umpteenth

time it's at royalastrosoc on twitter or you can email your questions to podcast at ras.ac.uk and we'll try and cover them in a future episode. And that's it for this month and for 2020. Can I just say thank you so much to everyone who has listened this year. We'll be back in January 2021, starting the new year with the beginning of everything, the Big Bang. Oh, yeah, I'm so excited. Now, at this point, I'd probably say happy stargazing to everybody, but Izzy, I've got something better for you. Are you ready for this?

Yeah. A Merry Christmas to all, and to got something better for you. Are you ready for this? Yeah. A Merry Christmas to all and to all a clear night. Love it.