Bonus: Rerun – Event Horizon Telescope

with Prof Roger Deane and Dr Rodhri Evans

The Cosmic Savannah team are off on summer holidays, but Jacinta drops by to wish you all happy holidays and introduce you to this re-run of Episode 5 from Season 1.

This episode is about black holes, in celebration of the 2020 Nobel Prize in Physics being awarded to 3 astrophysicists for their black hole-related research.

Roger and Rodhri tell us about the Event Horizon Telescope, used to make the first ever image of a black hole, and the African Millimetre Telescope, which will hopefully help to image the black hole at the centre of the Milky Way.

Have a happy and safe holidays and we hope you’ll join us again in 2021!

This time-lapse video from the NACO instrument on ESO’s Very Large Telescope in Chile shows stars orbiting the supermassive black hole that lies at the heart of the Milky Way over a period of nearly 20 years. Credit: ESO/MPE

Feature Image

Artist impression of stars undergoing a ‘slingshot’ orbit around the supermassive black hole at the centre of the Milky Way. Credit: ESO/M. Parsa/L. Calçada

Related links

This week’s guests

Transcription

Coming soon.

Episode 30: Pretty Planetary Nebulae

with Kelebogile Bonokwane

This week we’re joined by Kelebogile Bonokwane who is a National Astrophysics and Space Science Programme (NASSP) Master’s student at the South African Astronomical Observatory (SAAO).

Kelebogile talks with us about her MSc project on planetary nebulae. She is investigating whether binary stars sit at the heart of these magnificent structures and are responsible for their unusual shapes.

Her work utilises the Southern African Large Telescope (SALT) as well as NASA’s Transiting Exoplanet Survey Satellite (TESS). TESS is an all-sky survey mission designed to discover thousands of exoplanets around nearby bright stars. Kelebogile is using this data to study the central stars of planetary nebulae.

The “Starfish Nebula” Henize 2-47, a planetary nebula in Carina

Kelebogile was recently awarded the SAAO-SALT prize scholarship. She plans to do her PhD on X-ray binaries, investigating the relationship between X-ray and radio emission in order to study the accretion process and relativistic jet production.

This week’s guest

Feature Image

Planetary Nebulae He 2-47, NGC 5315, IC 4593, NGC 5307

Image Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA)

Related Links

NASSP is a multi-institutional postgraduate initiative funded by the Department of Science and Innovation (DSI) through the NRF. The aim of NASSP is to train graduates in astronomy, astrophysics and space science in order to contribute to national programmes. Learn more about NASSP here.

SALT: www.salt.ac.za

TESS: https://www.nasa.gov/tess-transiting-exoplanet-survey-satellite/

Acknowledgements

Social media by Sumari Hattingh.

Transcript

Jacinta: [00:00:00] Welcome to The Cosmic Savannah with Dr. Jacinta Delhaize

Dan: [00:00:08] and Dr. Daniel Cunnama. Each episode, we’ll be giving you a behind the scenes look at world-class astronomy and astrophysics happening under African skies.

Jacinta: [00:00:16] Let us introduce you to the people involved, the technology we use, the exciting work we do, and the fascinating discoveries we make.

Dan: [00:00:23] Sit back and relax as we take you on a safari through the skies

Jacinta: [00:00:36] Hello and welcome to episode 30!

Dan: [00:00:40] Yay! Happy…Birthday? Yeah, 30th episode. Can’t really call it a birthday.

Jacinta: [00:00:49] Season 3 Episode 30.

Oh, that’s nice.

Dan: [00:00:52] Sure.

Jacinta: [00:00:53] Okay. 30. Well, we’re both in our thirties.

Dan: [00:00:55] Yes. Hubble’s 30 years old. We’re talking about Hubble! Well just a little bit. We’re talking about planetary nebula. Hubble takes nice photos.

Jacinta: [00:01:04] So I guess it was launched back in 1990 then. Yeah. Do you remember that year, Dan?

Dan: [00:01:09] Do you remember that year? Now I’m feeling old. It’s my birthday next week, happy birthday to me! Well, actually it will have been my birthday and I’ll be 36.

Jacinta: [00:01:23] I don’t remember 1990.

Dan: [00:01:25] I shouldn’t be telling people my age. Right, back to the episode.

Jacinta: [00:01:31] Before we get into the episode, what have you been up to this week, Dan?

Dan: [00:01:34] I put in a proposal for another planetarium film!

Jacinta: [00:01:37] Did you?

Dan: [00:01:39] I did. I put a funding proposal in for another planetarium film. And this time inspired by episode 28, a couple of weeks ago. The proposal for this one is African star lore. Finished. 24 minute film on African star lore. Multicultural, multilingual.

It’s going to be huge.

Jacinta: [00:01:58] I can’t wait!

Dan: [00:02:00] Yeah. Let’s hope they give me the money. Money is hard to come by. Right? What have you been up to?

Jacinta: [00:02:05] I’ve been attending the 2020 SARAO Bursary Conference. And SARAO is the South African Radio Astronomical Observatory. This happens every year and you’ve probably heard several of our episodes in the past where we’ve interviewed other people who are attending those.

So this year, of course, it’s virtual, it’s online. Just as the SAAO recent conference was online and it’s actually working pretty well. This year we have all pre-recorded quick 90 second talks, which get played in succession. And then there’s a question and answer session where people can ask us questions live and we are online to answer them.

And then we meet in this thing called Gather Town, which I hadn’t heard of before. But you’re kind of like in a video game and you’ve got your little avatar of yourself and you walk around the spaces of this online conference venue and you meet other people there and you can talk to each other. Because it turns your videos on and your sound on you talk to each other and it’s working surprisingly well, I really feel like I’m walking around and seeing these people who are on opposite sides of the world at the moment.

Dan: [00:03:10] That is weird.

Jacinta: [00:03:11] Yeah. So really well done to the organizers.

Dan: [00:03:13] Well I’m glad it’s working out.

Jacinta: [00:03:14] Yeah, it’s cool.

Obviously it doesn’t beat real life, but this is what we have to do at the moment.

So it’s working nicely.

Dan: [00:03:22] 90 second talks though!

Jacinta: [00:03:24] Yeah. That’s very quick, but at least everyone’s getting a shot to talk. So this is mainly for the post-graduate students and the post-docs who are being supported by SARAO and we meet every year and we’re hearing all about the amazing discoveries and detections that MeerKAT has been making this year.

So I think this was maybe the first time ever that we’ve had a particular session, which was this morning, dedicated just to new MeerKAT results. So, yeah, it’s the first year that they’re all just churning out and so many people have made so many different discoveries and it’s really exciting.

Dan: [00:04:00] And every is going to need an extra session.

Jacinta: [00:04:02] Hopefully. Yeah. That’s what we’re after.

Okay, so let’s get back onto this episode’s topic.

Dan: [00:04:09] So today we will be discussing?

Jacinta: [00:04:11] Today we’re going to be discussing planetary nebula, which are the endpoint of stars that are not particularly massive. So stars that are similar to the sun or maybe around two solar masses, meaning two times the mass of the sun. These stars, they don’t die in these big dramatic supernova explosions, which we often talk about. Rather, they kind of fade away.

So they start burning different elements other than hydrogen. And then they release their outer layers, which just kind of float off into space. And they are kind of lit up by the central remaining star or white dwarf, I suppose. And they create some beautiful colors that we’ve seen in pictures, particularly from Hubble.

Dan: [00:04:56] Yeah. So there’s these sort of cloudy shapes around the central star, which are in numerous different colors once they’ve been tinted. I think the shapes are incredible. They’re definitely some of the most eye catching images that come out of Hubble.

Jacinta: [00:05:13] So who are we speaking with today about these planetary nebulae?

Dan: [00:05:15] So today we are joined by an MSc student. She’s just finishing her MSc project at the University of Cape Town. And her name is Kelebogile Bonokwane. And she is from Kimberly in the Northern Cape originally, where our telescopes are. Not in Kimberley itself, but in the Northern Cape. And she’ll be talking to us about her project and some of the telescopes she’s been working on.

Jacinta: [00:05:37] Just a couple of things to mention.

First, sometimes she calls planetary nebula, PN for short. We also have a little discussion about spectrometry and photometry. So Dan, what’s the difference between those two?

Dan: [00:05:50] Photometry is basically collecting little photons of light and measuring how bright they are. And spectrometry is collecting little photons of light and measuring their frequency or wavelength.

So you can split them up into their constituent frequencies and look at the colours and frequencies, and you can tell completely different things other than just the brightness.

Jacinta: [00:06:14] You can hear some wind in the background there.

Dan: [00:06:16] It’s Cape Town. It’s summer.

Jacinta: [00:06:18] It’s very windy in Cape Town in summer.

Right. So that’s the difference between spectrometry and photometry and I think that’s all we need to know.

So let’s hear from Kelebogile.

Dan: [00:06:36] Today we’re joined by Kelebogile Bonokwane. Hello Kelebogile. Welcome!

Kelebogile: [00:06:41] Hi, thanks for having me.

Jacinta: [00:06:42] Welcome to The Cosmic Savannah. It’s a pleasure to have you.

Kelebogile: [00:06:45] I’m glad to be here.

Jacinta: [00:06:46] Can you tell us first just a little bit about yourself? Who you are, where you’re from and what your role is?

Kelebogile: [00:06:52] I am Kelebogile Virginia Stephanie Bonokwane. My mother gave me many long names.

So I am from Kimberly in the Northern Cape. I grew up in sort of a Kgosi township of Galeshewe. And right now I’m a bit of a student in transit between Masters and PhD in astrophysics. Specifically stellar astrophysics.

Dan: [00:07:20] Where are you based?

Kelebogile: [00:07:21] I am at the UCT and SAAO.

Dan: [00:07:24] So split between the South African Astronomical Observatory here with me, and at the University of Cape Town.

Jacinta: [00:07:30] With me!

Kelebogile: [00:07:32] Yes.

Dan: [00:07:33] Maybe you could just tell us a little bit about how did you get into astronomy? Where did you study your undergrad?

Jacinta: [00:07:38] What got you interested in the first place?

Kelebogile: [00:07:40] So I remember very particularly, I think I was in grade four and we were learning about the telescope and Galileo Galilei and I was like wow this is interesting!

And I sort of had this astronomy thing in my head ever since. Although I went to a technical school. So we did electrical, civil and mechanical technologies. I was like okay, maybe I might become an engineer. But I decided to just pursue astronomy instead. That’s what I found interesting. I was like, I’m going to be a scientist.

And so that’s when I came to Cape Town from Kimberley. I’ve been at UCT since undergrad. And I did physics as well as astrophysics majors in undergrad. And I decided to just stick to and pursue astronomy. It’s what I found interesting. It’s what I liked. And I wanted to be at a point later in my career where I was doing research and I was doing something that I really liked and enjoyed.

And so I am here now sort of in my post-grad continuing with astronomy.

Jacinta: [00:08:49] That’s

awesome. So what do you study? What’s your research been about so far?

Kelebogile: [00:08:53] So it’s been planetary nebulae since honours. Since my honours project. And I sort of continued with that into my Master’s project.

Dan: [00:09:04] Can you just explain for the listeners, what is a planetary nebula?

Because it’s not what you think it is, right?

Kelebogile: [00:09:10] Similar to people, stars evolve over a lifetime. They’re born and they die. And so the planetary nebulae, they are where a star evolves towards the end of its life time. And what happens is inside stars you have this constant, continuous nuclear reactions happening.

And you have these elements formed. Hydrogen, helium, the first few elements on the periodic table. So what then happens when a star becomes a planetary nebula, is that there’s been so much gravity on the star itself, that the temperature rises enough to sort of drive off the surface material off the star.

It does this through very strong winds. And so you have this expanded material of guests driven off the surface of the star and then this hard core at the center, sort of heats up this material. And that’s what you see as this glowing nebula. So that whole system is what you have as a planetary nebula. The core at the centre and this glowing nebula around it.

Dan: [00:10:20] And they have nothing to do with planets.

Kelebogile: [00:10:24] No.

Jacinta: [00:10:25] Do you know why it was named that way?

Kelebogile: [00:10:27] I’m not sure.

Dan: [00:10:28] I do. Actually I do. I mean, it was the earliest astronomers, maybe 200 years ago. I think it might’ve been William Herschel even. They were looking at these objects or seeing them through small telescopes and they looked more planet like than star like.

Because they had this extra sort of shape and colour. They’re beautiful objects, planetary nebula. We’ll post some pictures on the website. But Hubble has taken some incredible photos of planetary nebula. So I think that was why they were called planetary nebula at first.

Jacinta: [00:11:05] So it was thought that they were from planets?

Dan: [00:11:07] It was thought that they were planets. Cloudy planets or something going around a round planet. But now we know that, as you said, they’re the end point of a star’s life and have nothing to do with planets. In fact, if there was a planet there, then that probably wouldn’t end very well for

it.

Jacinta: [00:11:23] So what do they actually look like, Kelebogile? Maybe you can tell us a bit more about the weird and wonderful shapes that they form.

Kelebogile: [00:11:31] Most planetary nebula are just spherical in structure or shape. But others have these bipolar lobes and jets, or these disks around the system. That’s what the ones look like that I’ve been studying. The sort of more interesting looking ones. The ones that have these interesting shapes that morphologies.

Jacinta: [00:11:57] And do you know why they have such strange shapes and morphologies?

Kelebogile: [00:12:01] Well, that’s sort of what we are trying to figure out. In the literature, it’s been speculated that it’s due to the stellar rotation and also others say that the magnetic field of the object can influence it. But those two scenarios don’t really support it, or wouldn’t be able to sustain that kind of shaping.

And so what’s been seen more recently is that there have been binary stars sort of discovered in these kinds of planetary nebulae. And so that’s what the basis of my research was. Trying to find binary central stars in these interesting PN  (Planetary nebulae) .

Dan: [00:12:45] Two stars within the planetary nebula itself? Or is the planetary nebula around the one star and the other star is further off?

Kelebogile: [00:12:53] Well, what you can have is the common envelope of the two stars. So most stars would reside inside of the common envelope and then the envelope can expand into the nebula and then sort of influence the shape like that. So that’s kind of what most simulations have modelled – how binaries can influence the shape of the planetary nebula.

Jacinta: [00:13:18] Okay. So there’s two stars in the very center and then the planetary nebula is very big and around both of them.

Kelebogile: [00:13:24] Yes.

Jacinta: [00:13:25] Okay.

Dan: [00:13:25] Oh right!

Jacinta: [00:13:26] Have you been looking into this problem with any particular planetary nebula?

Kelebogile: [00:13:31] Yes for my Master’s research, I looked at three objects. Hen3-1333,  Hen2-113 and Hen2-47. And Hen2-47 is the classically-known Starfish nebula. It looks like a starfish.

I looked at those because they were very interesting looking. They were all sort of multipolar in shape. So you had that interesting morphology, but also they had these extra features that added to how interesting they were and how they screamed that they must be binary central stars.

And that’s why I chose those objects. Those are the three that I looked at recently.

Dan: [00:14:15] And how are you observing them? Which telescopes are you using?

Kelebogile: [00:14:18] I used the South African Large Telescope SALT. And I also used the TESS telescope – the [Transiting] Exoplanet Survey Satellite, which is a space-based telescope. And the reason why I did that is because I wanted to do a very quantitative study.

So I got to spectroscopic data and also photometric data, to cover all bases.

Jacinta: [00:14:42] What kind of light does TESS collect? Is it optical light?

Kelebogile: [00:14:45] Yes.

Dan: [00:14:46] And it’s just collecting photometric data. So just brightnesses of stars, right? But it does that very regularly.

Kelebogile: [00:14:52] Yes, very.

Dan: [00:14:53] How regularly does it do it?

Kelebogile: [00:14:55] The data I had, it was taken at a 30 minute cadence.

And it does this continuously for about 27 and a half days.

Dan: [00:15:04] That’s amazing.

Jacinta: [00:15:05] So this satellite telescope is looking at the exoplanet every 30 minutes. Is that right?

Dan: [00:15:11] It’s looking at a field of the sky actually. So it’s looking at quite a large field of sky and it looks at it for 27 days consecutively taking an image every 30 minutes. So you’re looking at thousands of stars.

You didn’t use TESS specifically, you didn’t ask TESS to point for you. You’re just using TESS data, which they’ve released to you?

Jacinta: [00:15:31] From the archive?

Kelebogile: [00:15:32] Yes.

Jacinta: [00:15:33] And what did you find? What did you see?

Kelebogile: [00:15:35] Unfortunately, we had a non-detection in terms of finding the binary, but what we were able to do from our results is constrain the orbital period parameter.

And this is assuming that the features that we see, the shapes that we see, is because of a binary system.

Jacinta: [00:15:55] You were looking for a binary. You were trying to figure out whether these weird shapes were caused by binary stars at the center. You mentioned an orbital parameter. So you’re trying to find the amount of time it takes for the star to rotate around the other star?

Kelebogile: [00:16:09] Yes. And if you prove that does exist…

Jacinta: [00:16:13] then you’ve found a binary, right?

Kelebogile: [00:16:14] Yes.

Dan: [00:16:15] With the TESS data, you’re looking at the brightness of a star, or in this case the star at the center of a planetary nebula. And you’re looking for a change in its brightness, which will indicate that there’s another star there. Do these two stars have to be eclipsing?

I mean, does it have to be an eclipsing binary where the one passes behind the other in order for you to detect a dip in light?

Kelebogile: [00:16:37] It doesn’t necessarily have to be eclipsing, but you can tell from the sort of variation in the light curve that you make from this photometric data, if there is a signal detectable from that.

Jacinta: [00:16:54] Okay. So there could be some pattern in the light curve, even if it’s not eclipsing. Do you also look at the velocities of the stars? Like whether they’re actually wobbling?

Kelebogile: [00:17:03] Yes, so that was done with the spectroscopic data from SALT. I made radial velocity curves, and I had the light curves also to work from.

Jacinta: [00:17:15] Okay. So you’re looking at the variation in the light and whether the star is moving to figure out whether that’s a binary or not. Yes.

Dan: [00:17:22] So with SALT you’ve got a very high resolution spectrograph, a very high resolution spectrum. And from those lines, by looking at it at different times, presumably also fairly regularly, you can see  whether the star is moving towards or away from us. Correct?

Kelebogile: [00:17:38] Yes.

Dan: [00:17:39] And how regularly we were you doing that with SALT? How much data did you take from SALT?

Kelebogile: [00:17:44] It wasn’t an even sample, but the spectra that we had was taken over about 300 days. And so for the different objects, there was about 60, 58 and 35 amounts of observations. They were taken about 10 days between each observation. A little incoherent. So it was a bit of an uneven sample.

Dan: [00:18:11] So it was hard to find a sort of an easy period or pattern?

Kelebogile: [00:18:15] Yes.

Jacinta: [00:18:16] Were there any, maybe, slight hints of a binary?

Kelebogile: [00:18:20] There was for the Starfish nebula. There was this period that sort of stood out. It was 14 and a half days. What we do when we find a signal is that we try to phase up the light curve using that signal.

Jacinta: [00:18:36] Okay. So of the three planetary nebula you looked at to find binaries you’ve got “No. No. Maybe.” Is that right?

Kelebogile: [00:18:45] yes.

Dan: [00:18:46] Is the plan to carry on? Have you got plans to collect more data and try and clarify some of these things?

Kelebogile: [00:18:54] Well, because our results were saying no short periods, which is less than 10 days, we are assuming that they have very long orbital periods. And so we just need a little more data, or a lot more data! Because we have about three years of observations and we are assuming that the orbital period should be at least around thousands of days. So we need a lot more observations and monitoring with SALT to pin down if there is something.

Jacinta: [00:19:30] Okay. So your results don’t necessarily mean that there isn’t a binary. The obit of the stars around each other could be on a much longer time scale than you’ve already had a chance to look at.

Kelebogile: [00:19:40] Yes.

Dan: [00:19:40] And that wouldn’t be that long. If it’s a thousand days, that’s two and a half years or something.

That’s a slightly bigger orbit than the Earth, but not massive when you’re looking at two different stars. How big are these planetary nebula on the scale of the Solar System?

Kelebogile: [00:19:57] Very big. I guess if the Sun were to go into its planetary nebula phase, it might absorb Jupiter, I think.

Jacinta: [00:20:06] Oh, cool.

Kelebogile: [00:20:07] Yeah.

Dan: [00:20:09] That’s pretty big!

Jacinta: [00:20:10] Yeah!

Kelebogile: [00:20:12] And then there won’t be Earth by then.

Jacinta: [00:20:14] No. What would happen to the Earth?

Dan: [00:20:18] Vaporized.

Kelebogile: [00:20:19] Yeah.

Dan: [00:20:21] Vaporized.

Jacinta: [00:20:22] Yeah. I guess it would be already eaten up when the star becomes a red giant, right?

Kelebogile: [00:20:27] Yes.

Dan: [00:20:28] Is the sun expected to go into a planetary nebula phase? What are the requirements for a star to go into this phase?

Kelebogile: [00:20:36] Planetary nebulae progenitors, which are the first stages of the star are similar to the Sun. So they have similar masses, which is around two solar masses. So you would expect the Sun to follow the same evolution as a regular planetary nebula. So you would expect it to go into a planetary nebula phase.

Dan: [00:20:59] Yeah. So first it expands into this big red giant, and then that will kind of dissipate into a planetary nebula phase. Oh, that’s not a bad way to go.

Jacinta: [00:21:08] And do you know why they make all of these beautiful colors?

Kelebogile: [00:21:11] So it’s the elements often and then sometimes also the part of the spectrum it’s observed in. But for PN, from what I can tell, it’s mostly the elements.

So you have oxygen, nitrogen and sulfur making the blue, green, and red that you see. And those colors are sort of composites made. And then that’s how you see these different colors or what you would have perceived the PN to look like.

Jacinta: [00:21:44] So, do you think you would see those colors if you looked at it with your eyes or are they sort of false color images meant to represent the emission of different chemicals or elements inside the planetary nebula?

Kelebogile: [00:21:56] It would be because of that. False colors.

Jacinta: [00:21:58] Yeah. We spoke to Jayanne English a few episodes ago and she was actually one of the people at NASA who was making the image composites.

Dan: [00:22:06] And from Hubble too. So she presumably did play with some of the planetary nebula.

Jacinta: [00:22:11] Yeah, maybe even some of these planetary nebula. What are your plans for the future?

Kelebogile: [00:22:15] Well for now, I think I can only tell you about three or four years into the future.

Dan: [00:22:21] Oh, that’s more than I could say.

Kelebogile: [00:22:24] I’m starting my PhD next year, early next year. And that’s sort of going into a bit of a new field in X-ray binaries, working with X-ray and radio data. Which is something very, very new for me. But it’s an exciting challenge, I guess. But it’s still sort of sticking with stellar and binaries. Sort of a theme that I have going on.

Dan: [00:22:49] Where will you be doing that?

Kelebogile: [00:22:50] I will be at the SAAO. Okay, cool.

Jacinta: [00:22:53] Okay. Congratulations!

Okay, great. So I think when we’re nearly at the end now. Do you have any final messages for listeners?

Kelebogile: [00:23:00] Well, if they’re already listening and watching this, they’re already doing something good. But a message for them, I’d say, continue to listen and watch, learn about the science and whatever interests you in the field.

And also just continue to expose yourself to the different people that come here and tell you the paths they’ve taken to get to where they are. It can be something inspiring for you as an individual, regardless of whatever you are doing. And just continue to take care of yourself, stay safe with these times that we are in and be kind.

Jacinta: [00:23:42] That’s fantastic. Is that the advice you’d give yourself if you could go back in time and see little you when you were in grade four and interested in astronomy.

Kelebogile: [00:23:51] Yes.

Jacinta: [00:23:52] Great.

Dan: [00:23:53] Thank you. And thank you for your inspiration.

Kelebogile: [00:23:55] Thank you so much.

Dan: [00:23:56] It’s greatly appreciated.

Jacinta: [00:23:58] Yeah. Thank you very much for joining us and we hope to speak to you again soon.

Kelebogile: [00:24:01] It was nice being here.

Jacinta: [00:24:11] Okay. So interesting to know that these pictures of the planetary nebula, which have fascinated me since I was also very young, are false color images.

Dan: [00:24:19] Yeah. So we’ve discussed this previously, as you mentioned, episode 17 if you want to go back and listen, and we chat to somebody who does exactly that. So it’s more than just making up some false colors to make it look pretty. It’s not just sticking it into Photoshop and making it look nice. They actually try and hold onto the science. So adjust the image according to its frequencies and then use the different colors to represent those frequencies. So you actually, to use quite a big word, ‘elucidate’.

You shed light on what exactly is going on.

Jacinta: [00:24:52] Yeah.

Dan: [00:24:53] Yeah, a great chat to Kelebogile too. It’s really cool to hear stories of people who grew up in South Africa, getting interested in astronomy at a young age, and then having the opportunity to study it and become an astronomer. It’s really special and wonderful to see.

Jacinta: [00:25:10] Yeah, definitely.

Cool. All right. Well, it was really awesome to talk to Kelebogile. 

Dan: [00:25:15] Yeah, and we’ll let you get back to your Bursary Conference. Some exciting science I’m sure coming out and hopefully we can earmark some people to interview, including yourself. And l keep trying to get you to talk about your new paper.

Jacinta: [00:25:28] It’s not accepted yet, but as soon as it is…

Dan: [00:25:30] okay. Soon, soon, soon.

Jacinta: [00:25:32] Yeah. I’ll be the guest on one of the episodes.

Dan: [00:25:36] And do let us know if there’s anything else exciting coming out of the conference.

Jacinta: [00:25:40] Oh, there is. I’ve already written a whole list of people that we need to interview on what their topics were.

Dan: [00:25:44] Ah excellent.

Jacinta: [00:25:45] And I’ll let you get back to your funding proposals.

Dan: [00:25:47] Yeah. I’m just holding thumbs at this point,

Jacinta: [00:25:52] which for those not in South Africa means crossing fingers. That’s the very South African phrase.

Dan: [00:25:57] Oh right, yeah! I alway forget that that’s a South African thing.

Jacinta: [00:26:00] Okay. Well, that’s it for today. So thanks very much for listening and we hope you’ll join us again for the next episode of The Cosmic Savannah. You can visit our website, thecosmicsavannah.com where we will have the transcript, links and other stuff related to today’s episode. You can follow us on Twitter, Facebook, and Instagram @cosmicsavannah. That’s Savannah spelled S A V A N N A H.

Dan: [00:26:22] Special thanks today to Kelebogile Bonokwane for speaking with us.

Jacinta: [00:26:26] Thanks to our social media manager Sumari Hattingh and all the Cosmic Savannah volunteers.

Dan: [00:26:31] Also to Mark Allnut for the music production, Janus Brink and Michal Lyzcek for photography and Lana Ceraj for graphic design.

Jacinta: [00:26:38] We gratefully acknowledge support from the South African National Research Foundation, the South African Astronomical Observatory and the University of Cape Town Astronomy Department to help keep the podcast running.

Dan: [00:26:48] You can subscribe on Apple Podcasts, Spotify, or wherever you find your podcasts.

And if you’d like to help us out, please rate and review us and recommend us to a friend.

Jacinta: [00:26:56] We’ll speak to you next time on The Cosmic Savannah. [Music ends.]

Uh, and we also have a little discussion about photometry and spectromedy…Oh. [Laughs]

Dan: [00:27:14] Do you want to leave that in there?

Jacinta: [00:27:17] No, that can be for the bloopers.

Um…

Dan: [00:27:20] And that’s it for today. Thanks very much for listening and we hope you’ll join us again for the next step of the next ep… why is that one first?

Jacinta: [00:27:26] Cause that’s always first.

Dan: [00:27:27] Is it? It feels like it should be last.

Jacinta: [00:27:29] No, we have it again at the end. “We’ll speak to you next time on The Cosmic Savannah.” Don’t question the method now! We’re three seasons in! [Laughing]

Dan: [00:27:40] I was like, this doesn’t make sense. It seems so final!

Jacinta: [00:27:41] It does, doesn’t it?

Dan: [00:27:43] What’s TikTok? Should we join TikTok?

Jacinta: [00:27:45] I don’t know Dan.

Dan: [00:27:47] I don’t know. I’m 36 now.

Jacinta: [00:27:49] Yeah, I’m not going to say how old I am, but I’m a bit younger than you.

Dan: [00:27:53] Not far. [Laughing]

 

Episode 29: Zombies of the Cosmos

with Prof Matthew Bailes and Katia Moskvitch

This week we learn all about neutron stars and pulsars, which can be thought of as the “corpses” of dead giant stars.

We are firstly joined by Prof Matthew Bailes from the Centre for Astrophysics and Supercomputing at Australia’s Swinburne University of Technology. Matthew is a world expert on pulsars and the Director of the “OzGrav” ARC Centre of Excellence for Gravitational Wave Discovery.

Matthew chats with is us about pulsars, gravitational waves and some of the incredible science we can expect from projects such as Meertime. MeerTime will use the MeerKAT telescope to explore fundamental physics and astrophysics using radio pulsar timing.

We’re then joined by Katia Moskvitch, who was the 2019 British Science Journalist of the Year and the 2019 European Science Journalist of the Year!

Katia tells us about a her new book “Neutron stars: The Quest to Understand the Zombies of the Cosmos.” This popular science book is written for a general audience and describes the fascinating and bizarre existence of neutron stars and pulsars.

Katia is a highly experienced science writer and has worked at WIRED, Nature and BBC News Online, covering science and technology. Her work has also appeared in Quanta, The Economist, Science, New Scientist, Scientific American and many more!

We chat with Katia about science writing and the worldly adventures she had while doing research for her book. She takes us on a journey from the vast Atacama Desert in Chile to the Karoo semi-desert in South Africa and describes the people, telescopes and astronomy she encountered along the way.

This week’s guests

Feature Image

Artist’s impression of a magnetar – a highly energetic neutron star.

Related Links

Acknowledgements

Social media by Sumari Hattingh. Transcription by Brandon Engelbrecht.

Transcript

Dan: [00:00:00] Welcome to The Cosmic Savannah with Dr. Daniel Cunnama

Jacinta: [00:00:07] and Dr. Jacinta Delhaize. Each episode, we’ll be giving you a behind the scenes look at world-class astronomy and astrophysics happening under African skies.

Dan: [00:00:17] Let us introduce you to the people involved, the technology we use, the exciting work we do, and the fascinating discoveries we make.

Jacinta: [00:00:23] Sit back and relax. As we take you on a safari through the skies.

Jacinta: [00:00:34] Hi, welcome to episode 29, 

Dan: [00:00:36] 29. I was wondering what episode we were on. 

Jacinta: [00:00:38] So have you noticed it’s a bit more echo-y today, Dan? 

Dan: [00:00:40] It’s a lot more echo-y today. We apologize for that in advance 

Jacinta: [00:00:43] We didn’t bring the blankets for the blanket fort. So we’re sitting in Dan’s office and I think the blankets were actually helping.

Dan: [00:00:49] Yeah. COVID willing, we will hopefully be back in the studio soon.

Jacinta: [00:00:53] Hopefully. Right. So who do we have today? 

Dan: [00:00:56] So today we are joined by two people. Firstly, Professor Matthew Bailes, from the Swinburne Center for Astrophysics and Supercomputing in Australia. And then we are joined by Katia Moskvitch, who is a science journalist and the European Science Journalist of the year in 2019.

Jacinta: [00:01:16] This episode is all about pulsars and neutron stars. We’re talking to these two experts who are experts in different ways. So Matthew leads the MeerTime project with the MeerKAT telescope. So he’s going to tell us all about MeerTime and the observations they’re doing with MeerKAT and what they’re hoping to find with that, and Katia is , as you said, an award-winning writer and author, and she’s written a book about neutron stars.

So we’re going to hear from her as well. So first up, Dan, let’s just talk about what a pulsar is, what a neutron star is,  just briefly. 

Dan: [00:01:51] Yeah. So I think our guests will discuss it in detail, but we can talk about it quickly now. So a neutron star is the end point of a certain star’s evolution. So when stars die, largely by supernova, they form very dense objects, such as neutron stars, which are very, very small about 20 km across and spinning very rapidly and very, very dense. So it’s a few times the mass of our sun, but compressed into a 20 kilometre sphere. 

Jacinta: [00:02:20] And highly magnetized as well. 

Dan: [00:02:22] Yeah. So they’re spinning very fast and they’re emitting a lot of energy.

Jacinta: [00:02:25] And sometimes they are born in binary systems. So they’re orbiting with another star. And if one of them turns into a neutron star and the other ones remains a giant, then the neutron star can kind of pull some gas off the giant star and that causes some cataclysmic results and some nuclear explosions and all of these really cool things, which Matthew will talk about.

Dan: [00:02:50] Yeah, we’ve talked about X-ray Binaries and things before, about these sorts of systems where you’ve got a binary system with a neutron star. While neutron stars are very dense and an exciting branch of astronomy because they’re such an extreme case, very very dense objects moving very very rapidly.

And from that, that’s kind of always what we want and in astronomy, because we get a laboratory, which we can’t recreate here on Earth.

Jacinta: [00:03:17] Yeah, exactly. It’s one of the Universe’s most extreme examples of a particle accelerator and a magnet and moving relativistically, which means moving close to the speed of light.

As you said we can’t reproduce that on Earth. So we can only do some of these extreme tests with these astronomical laboratories, such as studying gravitation, gravitational theory, gravitational waves. 

Dan: [00:03:39] Yeah. So we will start off with Matthew. 

Jacinta: [00:03:42] Yeah so I think Matthew explains everything really well, especially about his use of the MeerKAT telescope, which is a radio telescope here in South Africa in the Karoo. I actually spoke to him at a conference in Durban. It was actually back in December when we were allowed to travel. So I spoke to him in person. So let’s hear from Matthew.

Jacinta: [00:04:03] Here with us now is Professor Matthew Bailes from the Swinburne University of Technology. Welcome Matthew. 

Matthew: [00:04:12] Hi Jacinta

Jacinta: [00:04:13] So Matthew, you are here with us in South Africa at the moment, but you are working and living in Australia. So what brings you here? 

Matthew: [00:04:20] Basically the greatest pulsar telescope in the world at the moment, MeerKAT.

Jacinta: [00:04:24] Well, I like that answer. But let’s backtrack a bit. So who are you, where are you from? What do you do? 

Matthew: [00:04:29] Well, I was born in Alice Springs in the middle of Australia, but I did my education at the University of Adelaide and the Australian National University. And while I was a student at Adelaide, I saw a book on pulsars and I learned about them and how they are really cool.

And I thought that sounded like fun. So I quit my engineering degree and moved into science and then ended up doing a PhD on pulsars and going to the Goddard Space Flight Center and Jodrell Bank in England and eventually back where I set up the Swinburne Center for Astrophysics and Supercomputing and have been having fun ever since.

Jacinta: [00:05:06] You set it up?

Matthew: [00:05:08] Yeah. I was the first astronomer to come over to Swinburne University of Technology and they asked me if I’d like to establish a new group. I don’t think they realized that there would be a hundred of us at some point in the future, but they’ve loved us and we’ve loved them. So it’s worked out very well.

Jacinta: [00:05:24] Well, that’s great. Yeah Swinburne is quite renowned in Australia. So congratulations on that. Now we are here at the SARAO Bursary Conference in Durban, in South Africa, and you’re here as an international guest speaker, and you gave I think the best astronomy talk I’ve ever seen. Immediately after which, I had to give my science presentation. So that was a really hard act to follow. Thanks for that Matthew. Now you were speaking all about just the sheer joy of pulsars. So let’s start with: what is a pulsar? 

Matthew: [00:05:54] So a pulsar is the collapse core of a once massive star, maybe 10 times bigger than our sun. Stars are big chemical factories and at the center, they convert hydrogen to helium and then helium to carbon.

And that process continues until you get an iron core. Which is about the size of the Earth, but maybe half a million times more heavy than the Earth, more dense as we’d like to say. And at that point, the poor old electrons and protons can no longer resist each other’s charms and they collapse to form a neutron and the core collapses down to something only about 20 kilometers in diameter and probably spinning about 50 times a second. That’s a naturally occurring particle accelerator and the particles that are accelerated from the surface of these neutron stars move in a changing magnetic field and then it gives off radio emission, and it acts like a big cosmic lighthouse. And every time that lighthouse goes past our telescopes, we get a pulse and hence the name pulsar.

Jacinta: [00:06:53] And why is it so cool to study pulsars? 

Matthew: [00:06:56] Well, if you look at the gravity on Earth, it’s actually pretty small by cosmic standards. We have an acceleration due to gravity of 9.8 meters per second squared. A neutron star is half a million times heavier. So that gives you a factor of 500,000 increase in the acceleration due to gravity.

But they’re also about a factor of 600 times smaller, and that’s a sort of R squared thing. So you’ve got these gravitational fields, you know, a million times stronger than on Earth and it’s a naturally occurring place to conduct studies into relativistic gravity, which is kind of why I get paid.

Jacinta: [00:07:33] Well, that’s a good enough reason to study pulsars. All right. So you are actually the principal investigator on a large survey project planned for the MeerKAT telescope, called MeerTime. So can you tell us about that? 

Matthew: [00:07:48] Yeah. So MeerTime is something that we came up with almost 10 years ago when they first called for large survey projects with the MeerKAT. We recognized that MeerKAT would have a good combination of collecting area, but also very high technology receivers, which are nice and cool. And that makes it the most sensitive pulsar telescope in the southern hemisphere and unfortunately pulsars are very weak. Your mobile phone has a transmitter on it, which is about half a Watt. The brightest pulsar is about 10 to the minus 26 Watts per square meter when the radiation arrives at the Earth, so you need a big telescope to be able to study them. 

Jacinta: [00:08:28] Okay. And so MeerKAT is that big telescope? 

Matthew: [00:08:30] Yeah. MeerKAT has 64 dishes, they are about 14 meters effectively in diameter and that gives it about four times the collecting area of the Parkes telescope, which is in Australia, which is one of my true loves.

I used that telescope for my PhD and most of my career, but it’s really exciting on the road to the SKA to have this quantum leap with MeerKAT. Just about four times the collecting area of Parkes and has these very nice, sort of chilly receivers you can think of on there, a few degrees cooler, than the ones on Parkes.

And so you really get this fantastic insight into the neutron stars that has been hinted at by Parkes, but now we’re sort of taking it to the next step with MeerKAT again. 

Jacinta: [00:09:12] Yeah, I think you and I actually met at Parkes for the first time. 

Matthew: [00:09:16] Oh really? Yeah. I remember an unsuccessful attempt to recruit you to Swinburne for a PhD Jacinta, but… 

Jacinta: [00:09:23] Oh, you brought that up! [Laughs]

Okay. So tell us about the goals of MeerTime. What in particular, are you trying to look at? 

Matthew: [00:09:31] Well, we’ve got four major projects and they’re actually headed by my colleagues that are distributed around the globe. And we recruited some of the best pulsar astronomers all the way from Italy to America or England and South Africa and Australia.

And the first project is to explore relativistic gravity. Michael Kramer from Germany and Ingrid Stairs from Canada are leading that project. And that’s to look at pulsars that not only are relativistic in their own right, but also going around another relativistic object, either a heavy white dwarf or another neutron star. And we’re mapping the orbits and seeing whether Einstein’s relativity theory works for those systems.

The second project is to look at swarms of pulsars that inhabit globular clusters. So globular clusters typically have a hundred thousand to a million stars in them. And the neutron stars in those clusters sink into the core where they interact with other stars. They actually scoop up matter.

And this makes them spin very quickly. And we have these swarms of millisecond pulsars. These are pulsars rotating up to about 700 times a second and MeerKAT peers into the heart of those clusters. And we examine the dynamics of those cluster pulsars. 

We have another project which is trying to detect gravitational waves using millisecond pulsars. This time not from the globular clusters, but from our own galaxy, more nearby ones. And we’re effectively using those millisecond pulsars as a giant galactic scale gravitational wave detector, a little bit like the LIGO detector detects kilohertz gravitational waves. We are actually looking at nanohertz gravitational waves from supermassive black holes in the local Universe.

And then finally, because we’re greedy, we have a project called the thousand pulsar array. Where we’re just looking at virtually every pulsar known to mankind and trying to examine the superfluid interiors of these neutron stars and how the pulsar emission mechanism works. 

Jacinta: [00:11:31] Okay. So there’s a lot of different science in there.

One question I had was when you were talking about relativistic pulsars and relativistic white dwarfs, what do you mean by that? 

Matthew: [00:11:41] On Earth you know, our velocities are typically measured in meters per second. Stars tend to move around each other in kilometers per second time velocities.

But if you get a really close pair of neutron stars, they can have a relative velocity of almost a thousand kilometers per second. This is a reasonable fraction of the speed of light. And if you try and use Newton’s laws to study those systems, they just break down. There’s also a compression of space-time around these relativistic objects and light takes longer to travel past these stars than it would otherwise.

And so we can see the curvature of space in the delays that we get from the pulses, from the neutron star. A kind of fun fact is that we’re able to measure the changes in these orbits to less than a millimeter per orbit when they go around each other, even though the orbits are hundreds of thousands of kilometers in diameter. 

Jacinta: [00:12:34] During your talk you mentioned that neutron stars can survive giant nuclear wars. What was that about? 

Matthew: [00:12:40] Yeah. So what happens is if you get a neutron star with a companion, that’s swelling up, big stars die and when they do, they swell up and become what we call a red giant. If the red giant has a neutron star orbiting it, then the neutron star will scoop up the matter.

The more boring companions that are lower mass, a bit like our Sun, leave you with a very circular orbit, which is not quite as exciting for studying relativity. But we like our neutron stars to have big companions that blow up and leave all sorts of exotic configurations that we can use to study and test relativity even more.

Jacinta: [00:13:18] Now your presentation had a lot of incredible visualizations and graphics and movies. How did you do that? 

Matthew: [00:13:23] Yeah, there’s a computer game engine called Unity, which is used for most of the mobile phone apps that you play computer games with. So we decided to make an astrophysical Universe, a game engine that had everything in space we could think of from planets to suns, to pulsars and black holes.

And then we just took the laws of physics and applied them. So we get true Keplerian orbits and beams of radiation and I’m part of an organization or a Center of Excellence called OzGrav, the ARC Center of Excellence for gravitational wave discovery. And we have a full-time programmer who makes these beautiful binary systems that I can fly around and engage with the public.

And you can actually sit there for hours and just like zoom around and come up with nice configurations. And then it makes for a very expert, very entertaining and visually rich feast for any audience. So I actually grew up and one of the reasons I’m doing astronomy was because I watched the cosmos television show when I was an impressionable young teenager.

Jacinta: [00:14:28] The Carl Sagan version?

Matthew: [00:14:29] Yes, definitely I am a big Carl fan. And then I just fell in love with that show and I loved the visualizations he had, but, I realized that with today’s technology, we could make much better ones and so at OzGrav we’ve got a team that makes these beautiful graphics and they’re really great to stand up and explain to people your science, without graphs and diagrams and astrophysical terms.

A picture paints a thousand words and animations are even better. 

Jacinta: [00:14:58] Yeah, it absolutely was. And there were people in the audience, senior people in the audience, who don’t necessarily have any love for pulsars, but really love galaxies. And you said at the end, does anyone want to come and work with me on pulsars?

And they were all like, yes! So we had some converts. So clearly your visualizations and your talk gave a really good impression. Do you have any final messages for listeners? 

Matthew: [00:15:19] Yeah. Look, I think one thing that your audience should realize is that the MeerKAT is a really great telescope. I was a little bit skeptical that a country as junior in radio astronomy as South Africa would be able to meet the technical challenges, but we’ve been delighted with its performance and the hospitality that the team has shown our group has we’ve come in.

But also very conscious of the fact that South Africa has somewhat of a tortured history. My own grandmother was South African. In fact, my auntie was born around the corner in Durban and they set sail for Australia about a hundred years ago. And we’d really like to be able to engage with as many young South African scientists and get them involved in this science. And one day make South Africa a powerhouse in pulsar astrophysics. 

Jacinta: [00:16:06] Let’s hope so. And I think you’re on the right track. Where can people find you on social media, on websites, for you and your MeerTime project? 

Matthew: [00:16:15] Yeah, so it’s www.meertime.org

Jacinta: [00:16:22] And then are you on Twitter? 

Matthew: [00:16:23] Yes, my Twitter tag is a very boring @matthewbailes.

I didn’t realize you had to have some cool name, so it might be too late now to change. 

Jacinta: [00:16:35] Don’t worry mine is @jdelhaize. Well, thank you very much for speaking with us, Matthew and for joining us here in Durban for this conference and safe travels home. 

Matthew: [00:16:44] Yeah, thanks for having me.

Jacinta: [00:16:56] So, what did you think of that Dan? A few of the things he said, very sort of casually and understated, but all of the science he’s talking about, this is Nobel prize winning stuff. 

Dan: [00:17:04] Yeah. I mean, it’s very exciting that the pulsar timing projects, you know, there’s been a lot of talk about gravitational waves in the last five years since their discovery, their first observation in 2015.

And we are sort of getting more and more gravitational waves discoveries. But being able to observe them passing through large swaths of The Milky Way by looking at the changes in the time of pulses. 

Jacinta: [00:17:33] It’s cosmic stuff.

Dan: [00:17:34] Yeah, exactly, no, it’s very exciting.

Jacinta: [00:17:37] Well I’ve got goosebumps now!

Dan: [00:17:40] The stuff we’re going to be able to see and discover with that level of precision observation is, ooooh I hope something comes out soon. 

Jacinta: [00:17:49] So this year’s Nobel prize in physics was for black holes. And next up: pulsars.

Dan: [00:17:55] A note to listeners that the Nobel Prize will really take some decades. So even if the science does come out in the next year, we won’t be seeing a Nobel Prize for some time. 

Jacinta: [00:18:05] That’s true. That’s true.

Okay. Who do we have next?

Dan: [00:18:09] Next we have Katia Moskvitch, who is a science journalist and science writer who has recently published a book entitled Neutron Stars, The Quest to Understand the Zombies of the Cosmos. 

Jacinta: [00:18:21] Yeah. So we both started reading that. I haven’t finished it yet, but I’m thinking so far that it’s really good.

Dan: [00:18:28] Yeah. I mean, it’s super engaging. I picked it up and I was like, oh, I don’t feel like reading a textbook. But it wasn’t. I mean, it’s not at all. It’s very well written. You get a story. You get drawn into the story very quickly. 

Jacinta: [00:18:42] Yeah I had the same reaction. I sort of was like, well, in my spare time, when I’m not doing astronomy or doing a podcast on astronomy, maybe I don’t actually want to read about astronomy, but this book was very engaging and it was about the stars, but also about the people behind the discoveries.

And so Katia is going to tell us a little about that.

Jacinta: [00:19:09] We’re joined now by Katia Moskvitch, the author of  Neutron Stars, The Quest to Understand the Zombies of the Cosmos. Welcome Katia. 

Katia: [00:19:17] Thank you. Hi. Hi again, I remember we met, what was it? A year ago? In Cape Town.

Jacinta: [00:19:22] Yeah. Back when travel was allowed.

Dan: [00:19:25] Was that part of this book? This research, that visit?

Katia: [00:19:28] The visit was exactly for the book. Yes, it was one of my stops, you know, my travels around the world for the book and I visited a number of really cool radio telescopes around the world. And when I was in South Africa, I went to see MeerKAT. Took me about 10 hours to drive there but yeah, it was really cool. 

Jacinta: [00:19:52] I’m so jealous. I still haven’t seen MeerKAT and I’ve lived here for two and a half years now! What was that like, Katia? 

Katia: [00:20:00] MeerKAT is amazing of course. I went there because I wanted to understand more about neutron stars. So the idea of the book and the idea of the travels as well, it goes back to when the publisher from Harvard University Press approached me and they said, okay, you can just write whatever.

At the time I was working on an article about the merger of two neutron stars that was for Quanta Magazine and I thought, okay, neutral stars could be a cool topic, especially if nobody’s really written about neutron stars before for a general audience. But then I thought, okay, well, how do I make it interesting for people because you know,  it’s quite far away. It’s quite abstract. We can’t really see them, they give off radio waves, but you know, like how do I make it appealing to the general public? And I thought, okay, well, if I actually go to all these places like MeerKAT and other observatories around the world that actually observed them, then I can describe what these instruments look like and how excited people get people who work there. Even though many scientists don’t go to radio observatories nowadays, because they of course operate telescopes remotely. But even then it doesn’t matter, because if I meet these people and I met quite a few people in Cape Town, they just get so excited, their eyes light up and they’re like, oh my God, this is so cool!

And it’s just so different compared to if you just talk to them on the phone. So that was the idea. And MeerKAT itself is 64 of these amazing, really cute dishes that all work together. It’s an amazing location as well. There’s no light pollution and it’s far away from any cities or anything.

And we just passed a few farm houses on their way. It’s so sensitive, it’s able to get signals from amazing objects in the sky. And it’s not even ready. Well MeerKAT is completely built, of course, but it’s a precursor to this much bigger project, the Square Kilometer Array and that one once it’s built, it’s going to be this humongous radio telescope in South Africa and Australia and once that’s built I really want to visit that as well. 

Jacinta: [00:22:15] For sure. I think that’s the first time I’ve heard the MeerKAT dishes described as cute, but I completely agree with you.

Dan: [00:22:22] Living up to their name. Did you see any meerkats while you were up there? 

Katia: [00:22:26] Any meerkats? No, I don’t remember seeing anything actually. I was told that there are scorpions. So I was told to wear, you know, special boots, like construction boots said so that a scorpion doesn’t sting or whatever, but I haven’t seen any actually.

Dan: [00:22:45] They are very cute too. You mentioned that your editor allowed you to write whatever you wanted. How did, how did you get into science writing?

How did you come to be at this point where you could write a book on science? 

Katia: [00:22:59] I’ve been a science journalist for many years now. I liked journalism. I’ve liked writing ever since I was a kid, but when I was in high school, I actually wanted to be an astronaut. It so happened that my high school was the same high school in Montreal where the second Canadian female astronaus went. Yeah, that was really cool. There are her portraits on the wall. So I wrote a letter to her at the time, I don’t think we had email yet, back then. Anyway, I wrote her like a real letter and she replied and I asked her how do I become an astronaut?

And she said, well, you’ll have to study science or engineering. So I went into engineering at McGill following her advice, but I realized I didn’t want to be an engineer actually, when I was in about my second year. And yeah, and they told me that my vision wasn’t good enough to be an astronaut either. So I was like, okay, well that kind of kills that dream.

But, then I decided to be a science writer. So I went and did a master’s in journalism. And my engineering degree really helped in terms of understanding what people were talking about. 

That’s how I got into science writing. But then I found myself writing more and more about space and astronomy and physics and I wasn’t understanding a lot of what I was writing about. And it was like, I don’t know what these people are talking about. It was really hard and frustrating as well. Because I had to translate it to the audiences. And if I didn’t get it myself then it’s so much harder to translate it to the audiences. 

So I decided to do a degree in physics then. I got my MPhil Master of Philosophy in theoretical physics. I remember coming to King’s College and I was at Nature at the time and I went to the director and I was like, you know what? I’m a journalist. I write about physics. I don’t understand anything. I need to get a degree. And he was so impressed. He said, yeah, I wish more journalists could get a science degree before getting into journalism because it’s so important. And so that’s how I got my physics degree. And just continuing from there, I started to specialize in astronomy specifically. And suddenly I received this LinkedIn message from an editor or a publisher at Harvard University Press, or a guy who says that he’s one of the editors there. And he’s like, do you want to write a book?

And I was like, okay, that’s so weird. That’s a LinkedIn message. It must be spam or something. I usually get marketing requests or some stupid stuff on LinkedIn. There’s no way it’s going to be true. But I Googled him, turns out he was a genuine editor. He just approached me via LinkedIn, which was really weird.

He said you can write whatever you like. And as I said before, at the time I was writing this big story on the merger of two neutron stars. So that’s how the book idea came along. Now I’m still writing about science but I kind of switched careers. I went from journalism into corporate communications and I write about quantum computing at IBM research. So still working with scientists, but not so much astronomy anymore, but still it’s still very cool. 

Dan: [00:26:08] That is very cool. And a reminder to me to check my LinkedIn messages. 

Jacinta: [00:26:14] Yeah me too!

Dan: [00:26:17] So the book it’s entitled Neutron Stars, the Quest to Understand the Zombies of the Cosmos. Now my first question was why is it Zombies of the cosmos?

Jacinta: [00:26:29] Dan has some qualms with this, but I don’t. Tell us how you came to that title, Katia?

Katia: [00:26:33] Right yeah, actually it took us a while. The publishing house had to come up with the right.

Zombies is a really, really fitting name actually for a neutron star. Because when you think about neutron stars, what are they? If you take a star, any star. If you take the Sun, for example. When the sun is going to die, it’s going to be really boring actually. So the sun, it’s just this medium-size star, actually on the smaller side of things.

So when it dies, it’s first gonna get a little bit bigger, turn into a red giant, and then it’s going to turn into a [white] dwarf, this really boring object. We can’t see it. You know, the Earth is not going to be around anyway around that time, but it’s just gonna stay there in space forever. Really boring. 

But if you take a bigger star, much bigger than the sun. So maybe eight times to twenty times more massive than the Sun. When that star dies, it really goes out and with a bang. There’s a supernova explosion, and it’s really pretty. We could see it with optical telescopes. And what stays behind is this compact object and that’s what we call a neutron star. 

So “zombies of the cosmos”, that’s because it’s a leftover core of a real star. So it’s actually dead because the star just died. It exploded in a supernova. And this tiny object – and by tiny, I mean really tiny. It’s actually about 20 kilometers across. So if you imagine, a city maybe like Cape Town, or even smaller than Cape Town, and you roll it up into a ball. Then you have this sphere, which is only 20 kilometers across and it’s spinning in space and it’s spinning like crazy, like maybe hundreds of revolutions a second, like 600 revolutions a second. And it’s also traveling at about 200 kilometers per second through space. When it’s spinning, it’s giving off radiation too.

So there’s no way we can actually see these stars because they don’t actually give off light at all. For the longest time, actually, they were completely theoretical. And only later were [found] completely by chance by this amazing woman in the UK, Jocelyn Bell. She was actually looking for something completely different with a radio array in Cambridge.

And she spotted radio waves like pulses from some unidentified object. And she didn’t know what it was and they actually kept it a secret for a while because they felt maybe these are aliens sending signals to Earth. And she was actually really annoyed about it because she was completing her PhD project, she was about to get married and there’s this bunch of aliens completely screwing this up!

She’s a really funny woman. She’s really amazing. I met her in the UK and she said something like, couldn’t they choose another planet to signal while I’m here working on my PhD thesis? Like really, she makes fun out of that. Anyway, she did detect the very first neutron star, a pulsar. We call them pulsars when we can detect the radiation from them.

Why pulsars? Because it’s just like a lighthouse. So a lighthouse when it’s turning it’s actually giving off continuous light but a ship can only see the light every second or so right because it’s turning. And if the ship is in the [line-of-sight] of the lighthouse, then it will see the light. And then again and again and again, flashes of light. 

Same with the pulsar as it’s spinning in space and it’s giving off this continuous radiation. But if our telescopes are in the field of view of the pulsar, then it will also get these pulses like beep beep beep. So this is what we receive, and this is coming from these dead leftover cores of a really massive star.Which I find completely amazing. I hope that answers your question properly.

Dan: [00:30:27] [Laughs] No, no, I get it. It’s great. I mean, I agree. I was trying to get my head around the undead nature of these stars.

Jacinta: [00:30:35] Why? It’s clearly a dead star! And then the star is undead but it’s a zombie because it’s still dead.

Dan: [00:30:41] No, no, no. I’m getting on board. I’m getting on board.

Jacinta: [00:30:48] Katia, you travelled to many places around the world to write this book and you met so many people. Tell us about some of your favourite experiences and the most interesting people you met.

Katia: [00:30:59] You mentioned that you spoke to Matthew Bailes, right? So Matthew Bailes is one of the main characters in the book because he is amazing.

He is such a great guy. And he’s the one who actually told me about the neutron star merger story way in the beginning, even before the book happened, when I was writing a story for Quanta. Before the Quanta story even happened. So I was at that conference in Jodrell Bank, which is one of the famous radio telescopes and it’s located near Manchester. 

So I was living in London at the time and I came to this conference. It was the 50th anniversary of the discovery of pulsars that I just described by Jocelyn Bell, which happened in 1967. I suddenly noticed that people are kind of discussing something in really hush hush tones and not telling me what the heck they’re talking about.

They’re kind of saying something in groups. And I was like, what is going on? There must be some big story, but nobody’s telling me. I missed my bus because I was interviewing somebody and I needed to go back to my Airbnb. And the telescope is a bit far away, you can’t just easily walk from the telescope to the nearest village or whatever.

And, so I’m standing there in the parking lot. What am I supposed to do? How am I going to get to my Airbnb? And this guy comes by and he’s like, if you want, I can give you a lift. And that was Matthew. And I’m like, yeah. And what do you do? And so we started talking and he’s like, okay, you’re a journalist.

And I told him, I was writing for Quanta at the time as a freelancer and Quanta is this quite reputable American publication. Usually the stories are really, really good. And scientists know that. They know that it’s not going to be, you know, dumbing down the science or anything like that.

So for him, that was a good sign. And he was like, okay, I’m going to tell you something, that’s going to be probably the biggest story of your career. I was like, okay. But he was very, very careful of course, and I talk about that in the book, because he is a member of LIGO collaboration. So LIGO is a huge collaboration of scientists looking for gravitational waves and just like any research collaboration or whatever, everything is under embargo. If there’s a big story, they have to check it and double check and triple check it and then publish the paper and peer review it and everything. And then it’s going to be made public.

So he said, using a lot of if’s and but’s, like if there was a neutron star and if it was to bump into another neutron star, then it would send off gravitational waves. And those gravitational waves would reach the Earth for the first time ever and prove Albert Einstein right and his theory of relativity and stuff.

And I was like, okay, he’s using a lot of if’s. He’s being really careful, but I think he’s trying to tell me something. And indeed he was. And so anyway, we ended up writing the story. We timed it perfectly for when embargo was lifted. So we didn’t leak anything and he knew we wouldn’t.

And that’s how that story happened. And that’s the story that I started the book with as well and the meeting with Matthew was crucial because then when I visited Australia, he actually took me from Melbourne all the way to Parkes, which is quite a cool road trip. We stopped in Canberra, in the capital, and we reached the amazing Parkes telescope in Australia.

Parkes is this quite old instrument now. It was built I think in the 1960s. It’s been upgraded actually recently, but it is this amazing radio dish. Completely different from MeerKAT. So MeerKAT is, as I said, 64 small antennas, but Parkes is one gigantic radio dish, which actually just happens to be also 64 meters in diameter, just a coincidence.

Anyway, what was really cool about Parkes specifically, was that the guy who works there, the telescope operator, he gave me a lift in the dish. So he invited me to step inside this gigantic 64 meter dish. And then another person who was in the control tower started lifting it up. So I was standing inside with this guy, John Sarkisian who works there, and suddenly you see the tree line disappear and you’re being lifted up in this gigantic soup bowl like telescope dish. So that was an unbelievable feeling. So that was Parkes.

But apart from that, I visited quite a few other places around the world. And so we can talk about them depending on what other questions you guys have.

Jacinta: [00:35:27] Yeah, that’s so cool. I did most of my PhD research with Parkes at Parkes, back in the day when you had to go there yourself and do the observations yourself.

So I also managed to do the same thing as you Katia, jump into the dish while it was moving upwards. And it was a lot of fun. What I’m really interested to hear in also is you went to the Atacama desert and Chile, didn’t you?

Katia: [00:35:48] Yes, exactly. I did. So Atacama is amazing. It’s the driest place on Earth. It’s not actually really, well, it is a desert, of course, but it’s not a desert the way I imagined it to be.

I thought it would be like sand, but I didn’t do my research properly. It’s not sand at all. It’s red and they have copper mines there. It’s full of copper. So when you drive through the Atacama it’s like this amazing Martian landscape. I think they actually filmed a few movies there as well to pretend that it’s Mars.

 It’s so remote and it’s in the Southern hemisphere, which is better for observations and there’s no light pollution. And also for some bizarre reason, I can’t remember now why, but there are not a lot of clouds. So for optical observations it’s great too, because the sky is so clear. So they have two really cool telescopes. Well, they have a lot of actually smaller telescopes, but two big ones that I visited.

One is Paranal, which is an optical telescope. But the one that was important for the book is called ALMA. And that one is the Atacama Large Millimeter-Submillimeter Array. So it’s also a cluster of dishes. It’s similar to MeerKAT, a little bit different in design, and they are located at five thousand meters altitude at a place called Chajnantor Plateau.

And it’s actually really cool because the air is very thin because it’s so high up. So we had to wear oxygen masks. And some locals gave me coca leaves too to chew because they said it helps from feeling dizzy, just chew the leaves. And I was like, is that even legal? But yeah it turns out it was fine. But yeah, in that amazing place they don’t really study neutron stars very often, but what they did study actually, and what I described in the book, is they looked at a supernova explosion and a neutron star being born in real time.

So they did all sorts of calculations and observations, and they think that they saw the object being formed by a star exploding and the neutron star being formed literally in real time. That was the first time that they observed it with a telescope. It’s not a hundred percent sure yet, they still have to do a lot of observations and calculations and everything.

But that’s what ALMA was really good for. And if it is confirmed, then it will be the first time that we can see a neutron star being born in real time, which is quite cool.

Jacinta: [00:38:09] That is so cool. To be able to watch a neutron star being born.

Dan: [00:38:14] Watching a star die and a zombie be born.

Jacinta: [00:38:18] Well maybe it’s a phoenix! Out of the ashes of the old comes the new.

Dan: [00:38:21] Phoenix is nice! Is that neutron star pulsing? Have they observed anything from it?

Katia: [00:38:30] They just found this engine, they  call it an engine. So there’s something that’s happening and they are not sure if it’s a black hole or neutron star inside the debris, the nebula, but most people think that a neutron star is a more likely explanation.

This is the difference. So not all stars actually give off radio waves. And that’s why there are two names. We kind of use them interchangeably, but not all neutron stars are pulsars. Some neutron stars are also magnetars so they can only be observed with x-ray detections. They don’t pulsate, they don’t give off radio waves actually at all.

Speaking of zombies, what’s very interesting, and I also talk about it in the book, is that there are neutron stars that die twice, which is really cool. So first you get this massive star, which will die. As I described before, it turns into a neutron star.

And then if it happens to be next to a companion star, what will happen as well, basically it starts cannibalizing the companion star and eating off the matter from the companion star and by doing so it will spin up, it will rotate faster and faster. And it will turn into what we call a millisecond pulsar.

And at that stage, we can’t see the radio waves anymore and we’ll be able to observe it differently. And then it can stop pulsating and kind of die again and then revive again. So anyway, it’s just the different stages that neutron stars go through. Not all of them do that, only those that have companions. I find it completely fascinating.

Jacinta: [00:40:13] Totally a phoenix!

Dan: [00:40:14] Yeah, rising from the ashes. Now we’ve got cannibal zombies. The zombie metaphor is really working for me now.

Jacinta: [00:40:25] Yeah. Pulsars and neutron stars are absolutely fascinating. And you can tell how passionate and interested you are.

Dan: [00:40:31] Yeah, I think it’s cool. I mean, they’re a very extreme stage of the Universe, right? It’s a very extreme environment that we’re looking at. So there’s really stuff that’s happening there, which you can’t see anywhere else in the Universe. And I think that that’s why it’s so cool.

Katia: [00:40:47] Yeah, exactly, they are incredibly dense. Black holes are of course the densest objects. But black holes are not [releasing] matter or radiation. And neutron stars are the densest objects that you can see that we know of.

Some of the visual descriptions I tried to use in the book for a lay audience to understand this. If you take the mass of the sun, and the sun is really, really huge, right? It’s much, much bigger than the Earth, but if you take all that mass and you put it inside a tiny object, which is only 20 kilometers across, you can imagine how much denser it will be. And this is a typical neutron star. Or if you take with your finger, if you scoop up a little bit of neutron star matter, then it will pull you down because it has a weight or mass of billions of tonnes, which is really amazing.

Dan: [00:41:38] You mentioned that you wrote this book. What’s next? Are you planning another book? Are we going to see more books in astronomy coming out of you?

Katia: [00:41:45] Possibly. I’m actually discussing a book with Harvard University Press right now, one of the chapters of this book deals with dark matter, which at first glance doesn’t even have a link to neutron stars, but actually there is. Just because there’s a signal coming out from our own Galactic Center – the center of  the Milky Way, that some people think could be from dark matter particles. Other people think that could be from thousands of pulsars that we can’t yet observe because our telescopes are not sensitive enough. So I kind of talk about this whole debate between dark matter, whether it’s dark matter or not. For that, I also visited a really cool dark matter detector in Italy, under a mountain range called Gran Sasso.

We haven’t yet detected any dark matter particles. We do think that dark matter exists and we have lots of theories and indirect observations of course with dark matter as well. But no direct detections. So I think it would be really cool, well now with COVID it’s a little bit tricky to travel, but once I can travel I would like to visit lots of other dark matter observatories around the world and possibly write a book on that.

So that will be really cool too.

Dan: [00:42:53] Maybe this will be an even bigger story in your life.

Jacinta: [00:42:56] Yeah. Maybe it will coincide with the discovery of what it is. So cool. So Katia, you won the European Science Writer of the Year last year, 2019. So congratulations. What advice would you have for listeners who might be interested in getting into science writing and journalism?

We often interview people on the academic pathway and how they interact with science, on this particular podcast. And this is a very different way of being a scientist and being involved in it. But outside academia, what advice would you have for listeners?

Katia: [00:43:34] Well, those who want to get into science writing if they already have a background in science, that’s great.

If they don’t have a background in science but a passion for science, that’s also great. I mean, the key is just to ask a lot of questions. As I said, before I got my degree in science, I only graduated last year, so I was writing about science for many, many years without a degree.

And it’s totally possible. You just have to ask a lot of questions and make sure that you understand what the scientist is telling you. And if you don’t understand, then you ask again. Because very often scientists, of course, they’re so close to their subject, that they may reply in very technical language using jargon.

But you just need to ask again and again, and maybe tell them even beforehand, look, this is for a general audience. If they still don’t get it, you could tell them. Look, okay, pretend you’re talking to your grandma. Or you’re talking to a friend in the bar. And your friend is really, really clever, but not a scientist, but maybe a lawyer.

And you really want your friend to understand your research? How do you do it? And this trick usually works. And I think once you get the interview out of the way, writing an article about science, if you’re passionate about it and if you like the subject is not that difficult.

Jacinta: [00:44:52] Awesome.

Dan: [00:44:53] Thank you Katia. Thank you once again for joining us, can you just tell the listeners quickly where they can get your book?

Katia: [00:44:59] Yes, of course it’s available on Amazon. Also, if you go to Harvard University Press or Harvard bookshop, you can read about it as well. But Amazon probably would be the easiest way.

Jacinta: [00:45:09] And where can listeners find you online?

Katia: [00:45:11] Listeners can always find me on Twitter. It’s @SciTech_Cat, or they can just put Katia Moskvitch into Google and you can find my Twitter or LinkedIn or other social media. And they can ask me any questions as well. I’m also very responsive on Twitter.

Jacinta: [00:45:27] Awesome. And did you have any final messages for our listeners?

Katia: [00:45:30] Well, I guess one message is that whoever wants to write about science always has to remember that there is no science without people. And this is very important because writing just about science is going to put many people to sleep.

Because even though science is cool, equations to many people who don’t understand them is not particularly interesting. But just remember, there is no science without people. If you write about people, if you put emotions in your story, then everybody will get excited.

Dan: [00:45:59] And there’s no science writing without people either. We’re very grateful for you.

Jacinta: [00:46:04] Yeah. And I can highly recommend the book. I am part way through it and it’s so well written and it’s very engaging. So thank you for putting it together Katia and thank you again for joining us on The Cosmic Savannah.

Katia: [00:46:16] Great, thank you guys for inviting me!

Dan: [00:46:23] Thanks Katia.

Okay. As we mentioned before, both of us have been enjoying the book thus far, and I certainly intend to carry on reading it and we hope you guys do too. So I can definitely recommend it. Very interesting to hear what went into it and very cool. The idea of going around and having the opportunities to go and see all of these telescopes first-hand and meet the people involved, it really does give you a completely different view of science, as she said. Science is nothing without the people and she’s bang on.

Jacinta: [00:46:59] Right? Yeah. And I like how she’s describing the day that the people had when they found out that the detection of the neutron star collision had happened and the gravitational wave signal. She talks to the scientists who wrote the papers, who made the discovery essentially.

And she describes the day that they were having before this. And then it suddenly happened and how it changed their lives very quickly. So I thought that was really fascinating.

All right. So I think that’s it for today. Great! Thanks very much for listening and we hope you’ll join us again for the next episode of The Cosmic Savannah.

Dan: [00:47:37] You can visit our website, thecosmicsavannah.com where we will have the transcript, links and other stuff related to today’s episode. And you can follow us on Twitter, Facebook, and Instagram @cosmicsavannah. That’s savannah is  spelled S A V A N N A H.

Jacinta: [00:47:52] Special thanks to Professor Matthew Bailes and Katia Moskvitch for speaking with us.

Dan: [00:47:56] Thanks to Sumari Hattingh and Liantsoa Randrianjanahari for social media support, Tim Roelf for show notes and preparation, and Sambatra Rahjohnson for transcription assistance.

Also to Mark Allnut for music production, Janus Brink and Michal Lyzcek for photography and Lana Ceraj for graphic design.

Jacinta: [00:48:16] We gratefully acknowledge support from the South African National Research Foundation, the South African Astronomical Observatory and the University of Cape Town astronomy department to help keep the podcast running.

Dan: [00:48:27] You can subscribe on Apple Podcasts, Spotify, or wherever you get your podcasts. And if you’d like to help us out, please rate and review us and recommend us to a friend.

Jacinta: [00:48:35] We’ll speak to you next time on The Cosmic Savannah.

Are you a convert now, Dan, to the zombie analogy? Tell me what your qualms were, I’m interested.

Dan: [00:48:56] My qualms were mainly the unscientific nature of a zombie. [Laughs]

It just feels like, I dunno, like are we allowed to call stars hobbit stars? Like. I dunno, we don’t, well, I don’t know. It’s not something  which is well formed in my mind, but I wouldn’t have used it.

Jacinta: [00:49:22] Well, I’ve written a blog post before about the neutron star collision and I used zombies.

So I’m a fan.

Dan: [00:49:31] Depending on what the titles for this is. You’ll see who won the fight.

Jacinta: [00:49:34] It’ll be zombies of the cosmos. Or zombies and phoenixes, either way.

Dan: [00:49:39] I like the phoenix, except that I…no I don’t like the phoenix that much either.

Uh, sorry. I’m a tough sell.

Jacinta: Bit of a grinch on this one. [laughs]