February 18 2021 will see NASA’s latest Mars Rover, Perseverance, land on the red planet.
We are joined by Tiaan Strydom, the Business Development Manager at the South African National Space Agency (SANSA) to discuss the landing and SANSA’s role in it, as well as various other contributions SANSA is making to space exploration.
During the landing, the rover will enter the thin Martian atmosphere at over 20,000 km/h. The rover will be slowed firstly by a parachute and then by boosters to slow the rover down to about 3 km/h.
Finally, the rover will land using a sky crane manoeuvre, the descent stage will lower the rover on three cables to land softly on six wheels at Jezero Crater.
Perseverance also is carrying a technology experiment – the Ingenuity Mars Helicopter – which will attempt the first powered, controlled flight on another planet.
Coverage of the landing will be streamed live from 21:15 SAST at the link below:
This week’s guest
An illustration of NASA’s Perseverance rover landing safely on Mars. (Credit: NASA/JPL)
In this episode we will be discussing some more exciting work being conducted with the MeerKAT radio telescope. We’re joined by Dr Paolo Serra from the Cagliari Astronomical Observatory in Italy. He is the principal investigator of the MeerKAT Fornax Survey.
The Fornax Cluster is a nearby galaxy cluster containing about 60 large galaxies and a similar number of dwarf galaxies. Astronomers have estimated that the centre of the Fornax Cluster is in the region 65 million light-years from Earth. It is one of the closest of such clusters beyond our Local Group of galaxies.
Paolo and his team are using the MeerKAT telescope astronomers to study the physics of gas that is accreting onto and being stripped off galaxies as they fall into the Fornax cluster.
They have already used this data to discover hydrogen gas getting stripped off a big radio galaxy, called Fornax A, at the cluster centre. This solves the mystery surrounding the whereabouts of the gas missing from Fornax A.
This week’s guest
Fornax A is a galaxy with a very active black hole in its core that is spraying radio waves out into enormous jets. Here, the white glow in the center is the visible galaxy NGC 1316 that you can see through the constellation of Fornax. Notice the wee spiral galaxy above it? These two galaxies are merging, and as gas and dust are stripped out of the small galaxy and poured into the center of NGC 1316, the black hole nestled there spins it up. How do we know this? The huge radio lobes to either side of this merger are the telltale signs that a black hole is being fed more than it can handle. These are the billowing ends of powerful jets shooting out spun-up, escaped material far into space. Credit: NRAO/AUI/NSF
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: [00:00:18] Let us introduce you to the people involved, the technology we use and the exciting work we do. And the fascinating discoveries we make.
Jacinta: [00:00:26] Sit back and relax as we take you on a safari through the skies.
Dan: [00:00:36] Right. Welcome to episode 32.
Jacinta: [00:00:38] Today we are talking about galaxy clusters. Our guest is Dr. Paolo Serra from the Cagliari Astronomical Observatory which is in Italy.
Dan: [00:00:50] And Paulo will be talking about a different galaxy survey. Last week, we spoke about the MIGHTEE Galaxy Survey with Jacinta. Jacinta, how did your press release go?
Jacinta: [00:01:01] It actually went really well. It was really amazing. There was a huge pickup from the media with dozens and dozens of articles from many different countries. There were radio interviews and TV interviews. There were ones in CNN and Forbes. So that was really cool. It was really exhausting though, I was in interviews one day from 5:00 AM until 11:00 PM. I’m not used to that. Dan, you do that much more often than I do.
Dan: [00:01:26] Yeah. It’s pretty exhausting. But I mean you did amazingly, I think you were on sort of every radio station you can think of and TV and news and you kept popping up all over the place.
Jacinta: [00:01:36] Yeah, it was exciting. I was really pleased to see that the general public and the media were really interested in the results in the work. And that everyone was really proud that South Africa’s MeerKAT telescope was doing such awesome things.
Dan: [00:01:51] Yeah, that’s awesome. I mean, I think we’ve said it many times that it is something really to be proud of and it’s great to see the public and the media getting on board with that and really enjoying what we’re putting out.
Jacinta: [00:02:01] Yeah, as you said, I was talking about the MIGHTEE Survey on MeerKAT last week. And today we’re going to hear about the Fornax Survey with MeerKAT that’s led by Dr. Paolo Serra, who is our guest today. He’s based in Italy where he has a research group and they use MeerKAT to look at a particular galaxy cluster cold Fornax. Dan, do you want to go through what a galaxy cluster is?
Dan: [00:02:29] We all know about stars; stars like our Sun and stars don’t come uniformly distributed across the Universe. They form in galaxies. So we have galaxies which consist of billions, hundreds of billions, of stars and those galaxies also aren’t uniformly distributed across the Universe. They form sometimes in voids and they’re very, very sparsely distributed, and sometimes they form in clusters. So in this case, we’ll be talking about galaxy clusters, which is a very dense region where there are many galaxies relatively close together.
Jacinta: [00:03:06] Yeah, exactly. And in this Fornax cluster at the very center, there’s a radio galaxy. Last week, we spoke all about radio galaxies and the discovery we made of two giant radio galaxies. This one in Fornax is called Fornax A, it’s not as big as the ones that we found, but it looks bigger on the sky because it’s a lot closer. Paolo is going to tell us about how his team used MeerKAT to look at the cluster and to look at this radio galaxy and what they hope to find with it.
Dan: [00:03:40] Yeah, sounds good.
Jacinta: [00:03:42] Shall we hear from Paolo?
Dan: [00:03:43] We shall.
Jacinta: [00:03:44] Hello with us today is Dr. Paolo Serra. Welcome Paolo.
Paolo: [00:03:54] Thank you.
Jacinta: [00:03:54] Can you tell us who you are and where you’re from and how you’re involved with Africa?
Paolo: [00:03:58] Sure. So indeed, I’m Paolo Serra. I’m an astronomer and I’ve been a professional astronomer for about 10, 15 years now. I’m originally from Italy though I did part of my studies in the Netherlands and then worked in Australia. I got involved a lot with South African astronomy and recently moved back to Italy where I work at the moment. My involvement with South African astronomy dates back from about 10 years ago when I started mostly working with collaborators based in South Africa. And eventually I think a big turning point for my connection with South Africa has been when the decision was taken to build a big new radio telescope in South Africa, in the Karoo desert. At that time, there was a call for projects from the international community. So I had an idea, submitted an idea for a project which was approved. And from that point on my engagement has increased a lot because I’m now leading a project, which is going to take data with the South African telescope called MeerKAT. And so I’m now from Italy and stay very closely connected and in fact, travel quite often to South Africa for this particular work.
Jacinta: [00:05:04] And how do you like your time in South Africa?
Paolo: [00:05:06] It’s wonderful. I wish I had more time to travel around there. I’ve been mostly to Cape Town to the big towns, say Cape Town, Joburg, Pretoria. Luckily once in a while we have meetings in some nice locations like Port Alfred – a few years ago. So that gives me a chance to do some road trips across the country, which is beautiful. And probably a highlight recently was a visit to the MeerKAT site itself in the Karoo desert.
Jacinta: [00:05:31] Oh wow, you got to go there?
Paolo: [00:05:32] Yeah. We flew there with a small plane from Cape Town and that was absolutely fantastic.
Jacinta: [00:05:37] So can you tell us a bit more about the survey that you are leading? What’s it called?
Paolo: [00:05:41] So the survey is called the MeerKAT Fornax Survey. It’s a survey of a particular system – astrophysical system – called the Fornax galaxy cluster. And hence, the name is done with the MeerKAT telescope. So the name just comes from the telescope and the system itself. The Fornax cluster is indeed a cluster of galaxies. And so I can explain that very briefly. You know that our Solar System is part of a galaxy, which is a collection of many tens of billions of stars. There are lots of galaxies in the Universe around us, you know, billions, tens of billions, hundreds of billions. And the key point of this project is that galaxies are not distributed uniformly across the universe. In other words, they are not all the same distance from one another, from the nearest neighbour. They can be very far from one another, in some regions of the Universe, which we call voids. They can be tens or hundreds of millions of light years from one another, but they can also in some regions of the Universe, be very close to one another in these places where lots of galaxies live pack together and in small volumes, relatively small volumes – are called galaxy clusters. In galaxy clusters you can have from hundreds to thousands of galaxies, all living again, as I said, very close to one another. And when they do so they interact with one another, quite a lot. There’s mashing to one another. Essentially they can destroy, disturb, deform one another, eventually also merge and make bigger galaxies by just merging with one another. And the other thing that they do is that they interact with the gas that lives in between them – the Universe is not empty. It’s filled with a very tenuous, but nevertheless, existing gas. In galaxy clusters this gas is relatively dense and hot. And it can disturb galaxies. And so this is a major way in which galaxies during the 15 or so billion years of the life of the Universe, change their appearance, change their properties, their composition, by interacting with one another and by interacting with the gas in between them. And in galaxy clusters, this happens at a very fast rate. It happens with particularly violent or dramatic events. And, and so studying a cluster like Fornax, which is very well visible from the MeerKAT site and is very close to us. So you can look at it in details – it’s very exciting and useful to understand the astrophysics that drives this galaxy evolution.
Jacinta: [00:08:04] Okay. So Fornax is a cluster of galaxies and you’ve just explained in wonderful detail what a cluster is. So Fornax is nearby.
Paolo: [00:08:12] Yeah.
Jacinta: [00:08:12] How close was it?
Paolo: [00:08:13] It’s about 60 million light years away.
Jacinta: [00:08:17] Okay.
Paolo: [00:08:18] Which on the scale of the Universe is quite close.
Jacinta: [00:08:20] Yeah, it’s basically next door.
Paolo: [00:08:21] It’s basically next door.
Jacinta: [00:08:23] And what’s so special about, this cluster? Why did you choose to look at it with MeerKAT?
Paolo: [00:08:27] The small distance from us is an important thing. The other important thing for this cluster is that clusters come in all kinds of shapes and sizes and masses. And what we know, what I’ve described earlier about the way galaxies evolve in clusters, how they interact with one another and with the gas in between – has been particularly well-studied for big clusters. But big clusters are only one type of clusters. Well, what we need to understand is, to understand how galaxies evolve across our entire range of cluster masses. And so Fornax is important here because it’s a relatively small cluster. And so there are two key aspects to it, which we’ve mentioned: the distance it’s close, so we can look at it in big details and really understand how galaxies evolve and it’s smaller than the typical classes that have been studied so far. So it’s a very important compliment to the understanding we have now of galaxy evolution in clusters.
Jacinta: [00:09:23] And what do you hope to find with your data looking at Fornax?
Paolo: [00:09:27] Yeah, there are a few key goals we have. One of them is to indeed study in more detail, how much galaxies interact with the gas in between them in a cluster of this size. Now this interaction depends on a number of properties of galaxies and the cluster itself. I mentioned that in clusters this gas is a bit dense, denser than in emptier regions of the Universe, how much this gas is able to disturb galaxies depends on this density. And it depends also by how fast galaxies move through this gas. It’s like this gas exerts a pressure, a wind, if you want. The same way that if you put your hand outside of your car window, when the car is driving, you feel this wind, the same thing happens to galaxies as they move through this gas. What is unclear for a cluster of this mass, like Fornax, is whether actually this wind is any relevant, whether it can do any damage to the cluster, we just don’t know. We know it can do lots of damage in bigger clusters but in a cluster, like Fornax, we don’t know. So it’s an important missing ingredient for our understanding of how galaxies evolve. These observations will be the first ones to actually answer that question for a cluster like Fornax. A bit of a longer shot, a more ambitious goal if you want, but still within reach probably, is that our observations we MeerKAT will be so sensitive. Now we might be able to detect cold gas, which is what MeerKAT can see for us at radio frequencies that is streaming from the intergalactic medium into galaxies in various regions of the Fornax cluster. And in that respect, our observation is an advantage because it’s very sensitive, but it also covers a relatively large area of the sky, which means we can actually trace this flow of gas, if it is there, over large distances, which is key to actually detect it.
Jacinta: [00:11:17] Is this like some sort of waterfall of gas back down onto the galaxies?
Paolo: [00:11:21] It’s essentially it is, it’s a combination of lots of different processes. There is some gas that flows back onto galaxies, like you said, that used to be in them and has been thrown out of galaxies through explosions of dying stars and then it can flow back, but it is gas that has never been inside a galaxy throughout the entire history of the Universe and is now for the first time flowing into them. And so it’s this kind of observation that’ll actually be able to tell us how much the relative importance of these two different components gas flowing back towards galaxies or gas that is for the first time flowing in.
Jacinta: [00:11:57] And why is it flowing in?
Paolo: [00:11:59] It’s gravity. Galaxies essentially have a strong mass. They are the most massive things in their surrounding, and that’s why they’re formed in the first place. And so they keep pulling matter towards them. And some of this matter is in the form of hydrogen gas that we detect with radio telescopes.
Jacinta: [00:12:15] And why do we need to know whether the gas is falling into the galaxy?
Paolo: [00:12:19] It’s because it will tell us something about the rate at which they grow. Also, gas is the material from which new stars form. So in a sense, a galaxy that stops creating new gas is like, you know, like a zombie, it will stop creating new material from which will form new stars. And so it will stop forming new stars and it means its own stars – the one that it already has – will keep on aging and aging and the galaxy will essentially stop being active and being rejuvenated. When a galaxy does create new gas, it can continue forming new generations of stars and keep being young and the shining blue in the sky while the old ones will shine bright.
Jacinta: [00:13:02] So the gas keeps the galaxy young. Great. And are there any particularly special galaxies in the Fornax cluster?
Paolo: [00:13:11] There is a few special galaxies, quite well-known to astronomers and probably also amateur astronomers around the world because, indeed the cluster is nearby, so you can actually observe its brightest galaxies, even with an amateur telescope and take nice pictures of them. There’s a few of them. One is, you know – not probably very exciting name – NGC 1365. It’s a beautiful spiral galaxy with a big bar connecting its spiral arms. It’s truly wonderful to see in the sky with dust lanes, stretching across the stellar body and large regions of star formation. Another very famous one is called Fornax A – the name comes again from the name of the cluster, which actually comes from the name of the constellation. And again, what you see is this cluster in this galaxy and the sky, it’s a constellation of Fornax. The galaxy itself is called Fornax A, because it’s a very powerful radio source. And that’s what astronomers have called “powerful radio sources”. You know, the name typically would come from the constellation where they are and then we add a letter; alphabetical letter. There’s only a few of them on the sky Centaurus A, Fornax A, Virgo A – just a few of them. Fornax A is one of the brightest radio sources in the sky and beautiful to see, but to see that you can’t use your naked eyes in that case, you need a radio telescope.
Jacinta: [00:14:29] Because our eyes can’t see radio light, right?
Paolo: [00:14:31] Exactly.
Jacinta: [00:14:32] And so we need radio telescopes to be our eyes.
Paolo: [00:14:34] Precisely.
Jacinta: [00:14:35] Great. And what’s going on in this galaxy?
Paolo: [00:14:37] In this galaxy, there’s lots of things going on. It looks beautiful. As in optical light, it looks very disturbed, very distorted. It doesn’t look like a galaxy that has been living on its own for a long time. So what we think has happened and what our colleagues think happened to this galaxy, is that it’s formed through a merger between two galaxies – two big galaxies roughly the same size – and this gives rise to a beautiful system where the central part has now relaxed, but the outer regions are still in the process of coming back into / towards the center of the galaxy and settling into the gravitational field of the galaxy itself. So in the optical light, that’s what you see. And so we think that this merger happened about 3 billion years ago. Ever since then, lots of small galaxies, other satellite galaxies, have been falling into a – what we call a merger remnant. The galaxy formed by the merger of two galaxies – two big galaxies – and all these galaxies bringing their own stars and their own gas and they sink towards the center of the big galaxy, Fornax A, itself. So they do a lot of things when they do that, they fuel new star formation in a sense, they bring in also themselves, new gas into this big galaxy. Some of this gas may actually make its way all the way to the central black hole of the galaxy itself. And this black hole, as it accretes matter, it attracts extremely fast, relativistic particles, electrons, for example. That is electrons that start spiraling in the magnetic field of the galaxy and they emit radiation at radio frequencies. And so these can dump energy again, back into the intergalactic medium. So we see this relativistic electrons at radio frequency – we see these two giant clouds, if you will, or what we call lobes; radio lobes of relativistic electrons, which are an indication indeed of a very active supermassive black hole at the centre of the galaxy.
Jacinta: [00:16:36] Cool. So you’ve got this huge cluster of galaxies – groups and groups of galaxies – there, and they’re all kind of moving through this gas and creating this wind and it’s messing up with the galaxies and then they’re all kind of crashing into each other and interacting and triggering supermassive black holes. So you’ve got a lot of crazy activity going on here in this cluster. But of course, when you look at it with the telescope, everything just looks like it’s staying still. Why?
Paolo: [00:17:07] Yeah, that is because all this fun processes that happen and that affect their life, actually have a very long timescale. They happen very slowly. I mentioned earlier that Fornax A formed through a merger between two big galaxies, about 3 billion years ago, and we see still now, 3 billion years later, parts of the galaxy still settling in after the merger happened. And so all these things take a long time. So whenever we look at a system like the Fornax cluster or NGC 1365 or Fornax A, we’re essentially seeing a snapshot of their life. And if we wanted to see some action, some real action – we would have to observe these systems for hundreds of millions of years, at least.
Jacinta: [00:17:50] Really? So even if we keep looking at this system for an entire lifetime, a human lifetime, we won’t see any change?
Paolo: [00:17:56] Absolutely. Well on some scales – maybe – in the very central engine here, these black holes, for example, they do vary over relatively fast timescales and that you can see with telescopes, but on the large-scale, you know, of the entire size of a galaxy or the entire size of a galaxy cluster, no, you won’t see a change, certainly not in a lifetime.
Jacinta: [00:18:17] Why not?
Paolo: [00:18:18] It’s just the speed at which things move. You know, the individual stars, if you will, it seems very fast to us. They move at hundreds of kilometers per second, but they need to cover distances of millions of light years. And that will take a long time. And that’s why we don’t see really these processes in action. And that’s why we need to observe as many galaxies as possible because each of them gives us a snapshot of their life. It’s like, if you wanted to get an idea of the evolution or the aging of a human by just observing a human for 10 seconds, of course you don’t get that. If you observe a few hundreds of them, you get kids, you get old people, you get teenagers, you get people in their forties, you get all that. Then you can try to piece that together into what might look like if you were able to see a single human aging from their birth to their death. That’s what we try to do.
Jacinta: [00:19:09] Yeah, that’s a really great analogy. So instead of watching one galaxy evolve, we just look at many different galaxies, which might be at different evolutionary stages and we try and come up with what the expected pathway is. Right?
Paolo: [00:19:20] Exactly.
Jacinta: [00:19:21] Yeah. Great. And so why do you want to use the MeerKAT telescope in particular to do this study?
Paolo: [00:19:27] So MeerKAT, as we mentioned before, it’s a radio telescope and we want a radio telescope in this case, because the radio telescope allows us to see hydrogen gas. Hydrogen is the most abundant element in the universe. It’s just hydrogen atoms, essentially free floating in a universe and interacting with one another through gravity and hydrodynamics. And they emit a single spectrum line of radiation. They emit electromagnetic radiation at thay specific frequency, which happens to fall in the radio radio frequencies.
It’s about 1,400 megahertz.
Jacinta: [00:20:05] About 21 centimeters wavelength, right? We can imagine what that is. Kind of the span of your big hand, maybe?
Paolo: [00:20:12] We can see that. Yeah. And so you need a radio telescope to see this radiation and MeerKAT is one of them. Now there is a few radio telescope in the world. Radio telescopes have been actually with us for several decades now.
And of course, as with everything else in human technology and research, they’re getting better and better with time. Now MeerKAT is one of the most recent and shiniest radio telescopes and its unique property is that it’s extremely, extremely sensitive. It is the most sensitive telescope we have radio telescope we have right now. It’s sitting there in the Karoo desert for us.
And so if you want to perform extremely sensitive observations of a relatively small region of the sky, MeerKAT is a telescope to use now, and it will be for several years in the future. And so that’s a, that’s exactly the kind of observations we wanted to take. Take extremely sensitive images of the hydrogen gas in the Fornax cluster, which is not too big on the sky. And the MeerKAT was definitely the telescope to use.
Jacinta: [00:21:16] And what do you think of the timescales involved in this survey?
Paolo: [00:21:19] Well you have to be patient when you start a project of this size. And that is something you need to be aware of.
As I mentioned, this entire thing started in about 2010, if I remember correctly. When we as the international community were invited to submit ideas for scientific projects on this telescope. And so that’s already almost 10 years ago. And you do that, and then the telescope needs still to be built, to be tested.
There is all kind of really cutting edge technology that goes into this cutting edge data processing, data handling, the big data that we all talk about now. Astronomy is deep into it. And so you need to understand that this is difficult, that it requires the work of large teams of people doing all kinds of different things, being coordinated by very capable people. And that they just take some time.
And you need to be good in the meanwhile to stay on top of the science we want to do adaptative it if that is necessary, but also enjoy the ride because it’s beautiful to see the progress and see how far you go from an initial idea of a few people maybe, to a giant system that involves the work of hundreds in the end.
Jacinta: [00:22:34] We wish you a lot of luck for your project and thank you for speaking to us today. We hope you’ll come back and speak to us and tell us what you’re discovering.
Paolo: [00:22:41] My pleasure. Thank you.
Jacinta: [00:22:51] So since I spoke with Paolo, their team have actually put out a few new, exciting papers with the results from there Fornax survey. One of the papers in particular was really big news. They found hydrogen gas in Fornax A, in that central radio galaxy, and it had been thought for a long time that this hydrogen gas should be there, but it had never been seen and no one understood why.
There was a lot of dust that had been detected, but none of the hydrogen gas and it should have been there. Because the thought is that Fornax A was formed by the collision of two galaxies, one of which was kind of similar to the Milky Way, which had a lot of dust, and also some of this hydrogen gas.
So the question was, where is this gas? What happened to it? It turns out it was there, but we just couldn’t see it before. And now with the MeerKAT telescope Paolo and his team found the gas in two huge tails coming out from the center of the galaxy.
Dan: [00:23:55] Was it coming out or was it going?
Jacinta: [00:23:56] In coming out, I think. In these
two big title tails, where the dust and the stars had been detected already. They’d been pulled off the main galaxies during the collision and formed these two big tails which often form when galaxies collide. This gas seemed to have been pulled off the galaxy. This wasn’t a gas that Paolo was looking for, the infalling gas. This was a bit different.
Dan: [00:24:22] Oh right. So when the galaxy is merging, it’s quite a violent collision and these galaxies kind of fling each other around and in that process sometimes the gas and even stars get flung out of the galaxy forming these tidal tails.
Jacinta: [00:24:38] Yeah, exactly. This is all part of the exciting life cycle of galaxies.
Dan: [00:24:43] Yeah, I think Paolo’s analogy was a brilliant one, comparing it to a human life. We really want to know where galaxies started, how they’ve evolved over the billions of years that they’ve been around and then what their end point is. And from that, we can learn about the things that make them up, the stars and the stellar populations and all the way down to the elements that make up you.
And the way we can do this is by looking at many many galaxies and the more we can look at and the deeper we can look with things like MeerKAT and future telescopes, the more we can learn, the better picture we have of each point.
Jacinta: [00:25:17] So much MeerKAT stuff, coming out. So much stuff, so exciting!
Dan: [00:25:23] Yeah and I think it’s just going to carry on, right?
There’s going to be more and more coming out of MeerKAT. It’s taking data at such a rate that it’s kind of hard to keep up.
Jacinta: [00:25:33] Yeah and then there’s going to be the SKA. That’s going to be next level. So much data.
Dan: [00:25:39] We’re going to have a lot of exciting news to come. You probably going to hear a lot more podcasts. We’ve had two in a row now, you’re probably going to hear a lot more podcasts from MeerKAT data as more and more discoveries get made, but we’ll try and bring you other news too, because the frontiers of astronomy are getting pushed.
Jacinta: [00:25:56] To keep gushing about meerKAT.
Dan: [00:25:59] Yeah. I mean, I think we can sort of bask in the honeymoon phase of MeerKAT, right?
Jacinta: [00:26:05] Well, I think that’s it for today. Thanks very much for listening and we hope you’ll join us again for the next episode of The Cosmic Savannah.
Dan: [00:26:13] As always, you can visit our website thecosmicsavannah.com were we will have the transcript, links and other stuff related to today’s episode. You can also follow us on Twitter, Facebook, Instagram @ cosmicsavannah that’s “savannah’ spelled S A V A N N A H.
Jacinta: [00:26:29] Special thanks today to Dr. Paolo Serra for speaking with us.
Dan: [00:26:33] Thanks to our social media manager, Sumari Hattingh and all The Cosmic Savannah volunteers. Also to Mark Allnutt for the music production, Janus Brink and Michal Lyzcek for photography and Lana Ceraj for the graphic design.
Jacinta: [00:26:46] 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: [00:26:58] 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: [00:27:06] We’ll speak to you next time on The Cosmic Savannah.
Happy 2021! We’re looking forward to another exciting year of astronomy!
This year we get off with a bang as our very own Jacinta has a new paper out and takes her turn in the hot seat to tell us all about it!
Along with her colleagues, she has been part of the discovery of two giant radio galaxies using South Africa’s powerful MeerKAT telescope.
These galaxies are amongst the largest single objects in the Universe and are thought to be quite rare. The fact that MeerKAT detected two of these monsters in a relatively small patch of the sky suggests that giant radio galaxies may actually be much more common than previously thought.
The two giant radio galaxies found with the MeerKAT telescope. In the background is the sky as seen in optical light. Overlaid in red is the radio light from the enormous radio galaxies, as seen by MeerKAT. Left: MGTC J095959.63+024608.6. Right: MGTC J100016.84+015133.0. Credit: I. Heywood (Oxford/Rhodes/SARAO).
Transcript by Lynette Delhaize.
Dan: [00:00:00] Welcome to The Cosmic Savannah with Dr Daniel Cunnama
Jacinta: [00:00:08] 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: [00:00:24] Sit back and relax as we take you on a safari through the skies.
Dan: [00:00:34] Welcome to episode 31. Happy New Year, everyone.
Jacinta: [00:00:38] Yeah, happy New Year!
Dan: [00:00:39] We are once again recording over zoom. We are socially distanced and confined pretty much to our homes. So apologies for any sound issues or slight delay or. Jacinta and I talking over each other.
Jacinta: [00:00:55] We’ve got a fancy new setup now where I’ve got a home recording USB microphone set up. Thanks mum! It was my Christmas present. And Dan has our usual recorder in his house.
Dan: [00:01:07] Well, if you’re listening to it, then it’s worked. Yeah. All right. So 2021 from an astronomical point of view…
Jacinta: [00:01:13] there’s a new rover landing on Mars this year, right?
Dan: [00:01:16] Yeah. The Perseverance Rover will be landing this year, which is always exciting. We spoke about it a little bit last year. That’s super cool. They’re a few months away, I think. The launch of the James Webb Space Telescope should finally be happening this year.
Jacinta: [00:01:30] Oh I can’t wait!
Dan: [00:01:32] I’m not holding my breath.
Yeah. It’s gone through numerous delays over the years, so we’ll see. That’ll be very, very exciting and very, very stressful launching something like this.
I’ll be watching that launch with bated breath. In terms of celestial events observable from Earth, there’s nothing major. There’s a small eclipse visible from Cape Town, the 4th of December.
Jacinta: [00:01:57] Luna or solar?
Dan: [00:01:59] Solar, a small solar eclipse. But it’s a very small percentage visible just from Cape Town, not the rest of South Africa and actually it’s centered over Antarctica, which is quite exciting. If you can manage to get there. I’m sure we’ll get a couple of good photos out of that one. So, yeah, I guess we should get going with today’s episode.
Jacinta: [00:02:18] Yes.
Dan: [00:02:19] And what do we have in store today?
Jacinta: [00:02:21] Who are we interviewing today?
Dan: [00:02:24] Well, it’s the moment you’ve all been waiting for and I’ve been waiting for for some time. Jacinta’s long awaited paper is finally out. And so we can talk about it. I guess there’s an embargo until today, until it comes out and you can tell us all about it. So Jacinta… welcome to The Cosmic Savannah!
Jacinta: [00:02:47] No, you’re meant to call me Dr. Delhaize. Remember? Cause I’m the guest.
Dan: [00:02:52] Well, wait, let me do it…The Esteemed Dr. Jacinta Delhaize, welcome to The Cosmic Savannah.
Jacinta: [00:03:00] Yes well, hi, nice to be here. I’m actually quite nervous. I guess this is what it feels like to be a guest on our show.
Dan: [00:03:07] Just relax. It’s a conversation. That’s what we tell our guests, right?
Jacinta: [00:03:11] Ok, chilling. Well, I guess, well, you have to ask the questions, don’t you?
Dan: [00:03:16] Yeah. I have to ask the questions this time.
Let’s get into it. Your paper, you have discovered well, you and your team have discovered two giant radio galaxies using the MeerKAT telescope. And these galaxies are amongst the largest single object in the universe and obviously quite rare.
Before we get into the discovery and what exactly it all means, I think we should do a sort of introduction to radio astronomy. Talk a little bit about what it is and how it differs from optical astronomy. What exactly are we looking at and how are we doing it?
Jacinta: [00:03:52] Sure. Okay, so astronomy uses the whole electromagnetic spectrum, some telescopes can detect optical light, which is the same light as we can see with our eyes.
So they’re just basically huge eyes, but then we can also have different telescopes that can see ultraviolet light, infrared, the whole range of wavelengths down to the lowest frequencies or the longest wavelengths, which are the radio. And radio telescopes kind of look like big satellite dishes. There are several around the world and a new one in South Africa is called MeerKAT.
That’s in the Karoo and it comprises of 64 individual dishes and combined together it’s called an interferometer, which is pretty much one of the best in the world, if not the best at what it does. This is a pretty new telescope. It was launched… What? June 2018?
Dan: [00:04:47] That’s correct.
Jacinta: [00:04:47] And since is starting to make some pretty cool discoveries, including this one that we’ve made.
Dan: [00:04:55] Yeah. So we’re basically looking at radio waves which are coming in. As you said, MeerKAT’s a 64 dish array. And the reason we do an array is because in order to detect these very long wavelengths, we’d ideally like to have a huge square kilometer big dish. But that’s kind of unfeasible. So instead we build these arrays and then combine the signals to simulate a much bigger telescope.
Jacinta: [00:05:26] Well, that’s getting towards the SKA which MeerKAT is the precursor of, but yes, that’s what we’re heading towards.
Dan: [00:05:32] I don’t know what the combined collecting area of MeerKAT is, but it’s pretty big. 64 dishes which are each kind of 13 meters big. You’ve spoken a little bit about MeerKAT launched in 2018.
What makes MeerKAT so special? Why is it so powerful and what are the technological advancements which we’ve seen from MeerKAT?
Jacinta: [00:05:52] The one thing about MeerKAT in particular is that it’s very, very sensitive, so it can pick up very, very faint light or light from very large distances. And this is because what we call the receivers, the part that received the light, the radio waves, these are cryogenically cooled and they perform even better than they were designed for. So this thing is really, really sensitive.
The other really good thing about MeerKAT is that because there are so many of these individual dishes, 64 of them, we can spread them out. Some close together, some really far apart. And the greater the number of different distances between telescopes the more completely you can see the sky.
So if you have telescopes that are closer together, if you have dishes that are closer together, you’re going to be able to see things on the sky that are much larger scale. And if you have telescopes that are further apart, you’re going to be able to see things on a smaller scale. And so because we have this whole range, we can see small features in the emission from the galaxies or from whatever we’re looking at. And we can see large features.
And the way this has helped to make the discovery that we’ve published today is that this makes the MeerKAT telescope really sensitive to what we call “diffuse emission”. This is kind of like large scale fuzzy stuff. That’s very, very faint and distributed over large patch of sky.
Dan: [00:07:17] Okay. So you mentioned your discovery. Let’s get into it. You’ve discovered two giant radio galaxies. Firstly, what is a radio galaxy and how does it sort of differ from a regular galaxy?
Jacinta: [00:07:29] Okay. So galaxies, as we know are big collections of stars and gas and dust and dark matter and such, and you might have what we call a normal galaxy or star forming galaxy, which is just chilling out and it’s forming stars and converting its gas into stars. And those stars go supernova and then etc.
But some galaxies are called active galactic nuclei. Most galaxies have a supermassive black hole in their center, and this black hole becomes active when you have stuff falling into the black hole. So whether that be gas or dust coming from the galaxy or coming from the intergalactic medium, which is the stuff between galaxies.
So this is trickling in into the black hole and it’s heating up a lot as it does so. Then we call this black hole active. We call this whole galaxy an AGN, an active galactic nucleus. This activity is emitting a huge amount of very high energy light. It can be emitted across the entire electromagnetic spectrum all the way from the gamma rays down to the radio.
And when you have a lot of radio emission coming from this region, it’s called a radio galaxy. And often this is in the form of two kind of beams coming usually above and below the plane of the galaxy itself. And we call these jets. There are relativistic particles. These are highly charged particles like electrons, which are traveling close to the speed of light and they are interacting with the magnetic field around the black hole.
These are spiraling in the magnetic field and emitting what we call synchrotron radiation, which is predominantly admitted in the radio. Right? So we have these huge beams of radio emission coming from above and below the black hole in these huge jets. And this is what a radio galaxy is.
Dan: [00:09:20] We really got you excited there didn’t we? Okay. It’s a lot to take in. So essentially a radio galaxy’s got the supermassive black hole at the center, which when it’s feeding, essentially taking in gas sometimes excites that gas and pushes out large jets of high energy particles, which we can detect in the radio wavelengths.
Jacinta: [00:09:48] Exactly.
Dan: [00:09:49] Okay. Got it. So what is a giant radio galaxy then?
Jacinta: [00:09:55] These jets of light, of which we will put a picture on the website for this episode. These huge radio jets, we think that they grow. So they start out small and then as the galaxy ages, they get bigger and bigger and bigger and bigger pushing further and further outwards from the galaxy.
They can come in a whole range of sizes. And the giant radio galaxies these are ones that are bigger than 700 kiloparsecs, which is around 22 times the size of our own galaxy, the Milky Way. So these are really truly enormous systems and these particular ones, we call giant radio galaxies.
They’re actually fairly rare. We’ve found hundreds of thousands, even millions of radio galaxies of all different sizes, but only about 800 or so of them are classified as giants. So relatively rare.
Dan: [00:10:44] Are they giant in mass or just giant in size?
Jacinta: [00:10:47] Giant in size. So we measured the size as the distance between the end of one radio jet and the end of the other. So the full extent.
Dan: [00:10:54] So they don’t necessarily have more stars in them. They’re just kind of more diffuse things.
Jacinta: [00:10:59] Yeah, exactly. So their end to end size is really enormous. The galaxy at the center, it can vary in what it looks like, but often it will be hosted by a galaxy that is what we call a red and dead elliptical.
So it’s an elliptical galaxy, which has very little gas in it and therefore it’s not forming many stars. So the stars that are inside it are kind of turning red because stars turn red as they age and without new stars forming that are blue, this whole galaxy looks red.
Dan: [00:11:26] Is that why these sort of large galaxies haven’t been detected before? I mean, is it because their stars aren’t quite so bright and they’re more diffuse?
Jacinta: [00:11:35] No. So what we call the “host” galaxy, the galaxy that is hosting the black hole and emitting the radio jets. That’s actually fairly bright. I mean, we can see it very clearly in the optical images, but what hasn’t been detected before is the radio emission.
The particular galaxies that we have found with MeerKAT, they have been found before in the radio wavelengths. So actually that was part of the work that I did in my previous postdoctoral research position in Croatia where we studied the same patch of sky with a telescope in New Mexico called the Very Large Array. And the benefit of the Very Large Array is that it has very, very good angular resolution.
That means that it can see details very, very clearly and very, very small details. And in that data, you can see these galaxies, you can see the radio jets, but only the inner parts of them, the very, very inner parts. So in that data, these look like radio galaxies, but not giants, just kind of small ones. So we’d found them before and we’d found their elliptical host galaxies, but they just looked small. What we found in the new data is that not only do they have these little inner jets, they’ve got these huge, enormous outer jets, many, many, many times bigger than the previous ones that were found. And so that’s how we now know that these are giant radio galaxies.
And it’s because of the excellent MeerKAT sensitivity to diffuse emission, which I said at the start, the ability to detect large scale, very faint emission or light on the sky. That’s why we can now pick up the giant lobes of this galaxy. Whereas we couldn’t see it in other data from telescopes like the Very Large Array or from the Giant Meter-wave Radio Telescope in India, which has also looked at this particular patch of sky called COSMOS.
Dan: [00:13:25] All right so you haven’t discovered new galaxies. You’ve just discovered a larger radio emission, a more diffuse radio emission than has been discovered before from these galaxies. And they’re not necessarily giant galaxies, although they are big, but they’re giant in the radio.
Jacinta: [00:13:42] Well, it depends what you mean by galaxy.
What do you mean by a giant galaxy? Classically that’s considered to be the size of the part of the galaxy that contains all the stars. But all of these radio jets, this plasma, this is also part of the galaxy.
Dan: [00:13:57] Ah touche.
Jacinta: [00:13:58] But we haven’t really considered that to be the size of galaxies before, because we couldn’t actually see it.
Dan: [00:14:03] Ah but then, I mean, you know, there could be this diffuse emission around all galaxies, but it’s just not getting lit up.
Jacinta: [00:14:10] Well, we’re looking with MeerKAT now, and we’re not finding that except for in a few examples such as these.
Dan: [00:14:16] Yeah. Then that leads me onto my next question. What does this mean for galaxy formation and evolution or our understanding of it?
Jacinta: [00:14:24] Okay. So, yeah, that’s a good question. There’s actually something else special about these galaxies and not only are they giants that hadn’t been identified as giants before, they’re also particularly special giants. We had a look at how these compare to other giant radio galaxies in size and what we call “luminosity” or “power”. By luminosity or power we mean kind of how bright the radio waves are, how much emission is coming from them. And they’re actually really quite faint. So we’ve found galaxies that are much larger and a bit fainter than most other giant radio galaxies that have been found. This means that they are quite unique objects and it probably means that there’s a lot more of them out there. There might be this extra population of giant radio galaxies out there that we haven’t seen before, simply because our telescopes couldn’t pick up this diffuse light, which MeerKAT can now see. This would actually match what we have predicted from models of how these radio galaxies evolve over time.
As I’ve said, we think that these radio jets, they start off small, so contained quite close to the stars, but then they grow outwards over time. If this is really why some galaxies become giants, then this would mean that we should see quite a lot more giant radio galaxies than we are actually seeing.
So it looks like they are there. We just hadn’t seen them before because of the limitations of our telescopes. And this is all information we need in order to understand how galaxies evolve or change over time, over cosmic time, since they were formed after the Big Bang till now. We need to understand all of these different physical processes that are going into them to understand the whole picture of galaxy formation and evolution.
Dan: [00:16:16] Yeah and you mentioned that, you know that there could be other giant radio galaxies like this, and we should be detecting them. These galaxies you detected, and you’re part of a survey called MIGHTEE, and presumably the MIGHTEE survey is going to carry on and is expected to detect many more of these. Can you just explain a little bit about MIGHTEE? What does it stand for firstly, and then what is its goal? What can we expect coming out from the survey in the next few years?
Jacinta: [00:16:46] MIGHTEE, that’s an acronym which I’ve just had to look up because I can never remember it.
It stands for the MeerKAT International Gigahertz Tiered Extragalactic Exploration survey. So mightee: M I G H T E E. And this is a galaxy evolution survey planned with MeerKAT and underway. So initially when MeerKAT was being planned there were several large survey projects planned. So international astronomers got together and formed collaborations and decided what most of the time on MeerKAT was going to be spent doing. And they sent in proposals. And the plan for MIGHTEE was one of them.
This was to create a really large scale galaxy evolution survey. Now, what does that mean? It means that MeerKAT is looking at several large patches of sky. In total it’ll be about 20 square degrees. Now to give you an idea, the area of the full moon is about half a square degree. Fairly large patches of sky.
And their goal here is to pick up the radio light from many hundreds of thousands of galaxies. And in doing that, you can study for example, the hydrogen gas, the neutral gas within these galaxies, which is the raw fuel of star formation, which we have spoken about a few times previously on The Cosmic Savannah.
And you can also study what I mentioned earlier, the synchrotron emission. So that’s this special lightgenerated by these electrons moving really fast in the magnetic fields. Sort of weird other things like polarization, where the direction of the light, the angle of the light is changing, but we don’t need to go into all of those details.
There’s a lot of different components of this MIGHTEE survey, but it started off with Early Science observations or Pilot observations. So this is just to check whether everything’s going right. These are the first set of observations to see if the survey has been well-planned. So to do that, MIGHTEE looked at one patch of sky one square degrees in size. So about four full moons can fit into that region.
And we looked at a particular patch of sky called COSMOS, as I mentioned earlier, and this patch of sky has been looked at by many other different telescopes in the past, in the radio light, in the x-rays in ultraviolet, in the infrared. And so we have a lot of data to compare with.
That’s important because all of this extra types of data that can let us figure out how far away these galaxies are. And once we’ve done that, we can have a look at how much light we’re detecting from them. And we can figure out what the actual strength of the light is because of course if you’ve got a galaxy that is close to you, but a bit faint, it’s going to look the same brightness as a galaxy that is further away from you and quite bright.
One of the things that we found straightaway when we looked at this early science data and of the COSMOS field was we spotted these two huge extended objects. Which turned out to be these giant radio galaxies that I have published a paper on. And they really looked fantastic. We’ll post a picture on the website of a cutout from the radio map of the sky that MIGHTEE made. And you can see really clearly these big streaks, these fuzzy streaks across the sky. And those are these giant radio galaxies that we found. Now, this was really exciting because if there are only, let’s say about 800 giant radio galaxies known, and a lot of these have been found with the LOFAR telescope, which stands for the Low Frequency Array, which is sort of based in the Netherlands and Europe. With that telescope most of these giant radio galaxies were found, and we looked at how they were distributed across the sky. And based on that, we really didn’t suspect to find even one giant radio galaxy in this tiny one square degree patch of sky that we looked at. The fact that we found two is incredible. The probability of finding two, based on what we know about the distribution on the sky of giant radio galaxies, is very, very, very small. Incredibly small.
So either we have been insanely lucky to find these, or there are many more giant radio galaxies than we previously knew. And so that’s how we came up with this very exciting conclusion that there may be many more than we knew before. And that we’re starting to find them now with surveys like MIGHTEE, that are able to detect this very faint diffuse emission because of how sensitive they are.
Dan: [00:21:10] That’s super cool. And how much of the sky is MIGHTEE going to look at and how long is it going to take and how many of these things can we expect?
Jacinta: [00:21:21] So it’s going to look at in total 20 square degrees. So for comparison, what I’m talking about was one square degrees. These early observations, which four full moons will fit into it.
So you times that by 20 that’s how big ultimately the field will be. It’ll take several hours. So the observations that we looked at of the COSMOS field, actually they took only about less than 24 hours. So it’s actually incredible how sensitive this MeerKAT telescope is because the same patch of sky with the Very Large Array we had to look at for 400 hours with the Very Large Array before we could get to the same level of sensitivity.
So it’s going to take quite a few more hours to finish the whole survey. But the thing is we have to share the telescope. So not all of the observations can be dedicated just to MIGHTEE. We have to share with other surveys.
Dan: [00:22:12] You’re not going to get 20 days straight up.
Jacinta: [00:22:14] No.
Dan: [00:22:15] It’s probably just as well otherwise you’d have a lot of work.
Jacinta: [00:22:19] Yeah. Right. Of course, this is definitely not just me doing it. This is an international team of several dozens of astronomers. This is led by Matt Jarvis at the University of Oxford and Russ Taylor at the University of Cape Town. And then there are many other people who work very, very hard on this, including Ian Heywood, who is the second author on my paper and many others.
So yeah, not just me.
Dan: [00:22:44] MeerKAT is a precursor to the Square Kilometer Array which we mentioned earlier, and that’s going to be coming in the next five or 10 years. Recently the SKA was ratified. There’s many, many partner countries involved, and I think the final signatures happened in December.
So it’s, it’s official now that the SKA is an international organization. There’s a treaty and construction can now start on the SKA. That’s obviously going to be even more sensitive than MeerKAT. What are you looking forward to from SKA in terms of this kind of research in this field?
Jacinta: [00:23:27] Yeah, that’s a good question.
So the SKA is just so incredibly exciting. Of course, it’s going to be built partly in South Africa and partly in Western Australia. Each of those two components of the SKA will detect slightly different frequencies of the radio light. And it’s going to be, I think, revolutionary for our understanding of galaxy evolution, our understanding of radio galaxies, and radio astronomy because it will combine the best qualities of all the different telescopes in the world.
So the best qualities of the Very Large Array, the VLA, the best qualities of MeerKAT and ASKAP in Australia. MeerKAT, as I’ve said, is very good at detecting diffuse emission. So it’s very good at detecting large scale things.
And it’s very, very sensitive. It has good angular resolution, meaning it can see smaller details, but not as good as the VLA. So the VLA has really good angular resolution. The SKA will have both will have everything, right? So it’s going to be very, very sensitive, even more sensitive than MeerKAT by many times.
And it’s going to have really amazing angular resolution. So can see very, very small details. If you can see details that are very, very small and very, very faint, you can see things that are very far away and everything in between there. And of course, as you’re looking further and further away, you’re looking back in time because of the amount of time it takes for light to travel to the Earth.
So we’re going to have this amazing new crisp view of the Universe as seen in the radio light. And I can’t wait to see what will happen. And hopefully not only will MeerKAT detect many more of these giant radio galaxies. So hopefully we’re even going to find more in MIGHTEE in the other fields that haven’t been looked at yet.
But then with the SKA who knows what we’ll find? Maybe we’ll find extra giant radio galaxies, or I dunno, what would we call them? Uh, humongous giant radio galaxy, or something like that.
Dan: [00:25:22] We’ve got a few years to try and come up with a good name.
Jacinta: [00:25:24] Yeah. I clearly, I’m not very good at naming, so we’ll have to do a workshop on that.
Dan: [00:25:31] Okay. Well, Dr. Delhaize, thank you very much for joining us on The Cosmic Savannah.
Jacinta: [00:25:37] It was a pleasure to be here, Dan. Thanks. It’s so weird!
Dan: [00:25:42] Congratulations on your paper. Well done for getting it out. That’s quite an achievement. It’s super exciting.
Jacinta: [00:25:48] Thank you. It’s been a long haul.
Dan: [00:25:51] Maybe we can just explain to the listeners, I mean, what does it mean to get a paper?
It’s not like an article in the newspaper, right?
Jacinta: [00:25:57] No. Yeah. And why it takes so long as well.
So a scientific publication or a paper is the goal of your work as an academic. It’s to make a discovery or a finding and then publish it. So tell other people. And the whole process can take several years. It can be very quick if you are very, very, very lucky and very efficient, but usually it takes several years. The way that it works for me, because I’m an observational astronomer is I wait for the telescope to take the data and I wait for team members to process the data. Because it doesn’t come out of the telescope looking like a nice, pretty map. You have to do a lot of complicated things to turn it into an image of the sky. And then you kind of look at that data and you find something interesting and then you analyze it. So this is usually using a lot of coding and a lot of programming.
And doing the analysis. So applying knowledge of astrophysics. So this is where your knowledge of physics and maths comes in. You read a lot of other people’s papers. You can’t just read textbooks on the topic to understand the research the field that you’re in because the textbooks aren’t updated quickly enough to be cutting edge because papers are coming out every single day with newer and newer and newer research.
And you have to be really up to date on the very latest stuff in this research field that you’re working on. So you have to go and read all of these papers and understand what the cutting edge is. And then you have to start to write your paper. You write up your discoveries and what you found, you compare it to what other people have published in the literature before.
And then you finish writing this paper. So mine is about 15 pages, but you can have shorter papers. You can have longer papers. That’s about an average size, I’d say about 15 pages with very, very small font and double columns and figures and pictures in it and everything. And then you submit it to a journal. And a journal is a…how would you describe a journal, Dan? I’ve never really been sure how to describe them.
Dan: [00:28:01] It’s a publication, you know. It’s like a newspaper, except it’s a formal publication, which comes out generally once a month from an organization which collects and processes these papers. So they keep a record of all of the papers, which get published.
Jacinta: [00:28:21] And it used to actually be published in an actual journal, an actual magazine sort of thing, which was sent out to all of the institutes.
But now of course, most of it’s just online because we all got access to the internet. We can just download all of the papers. We can save paper, save some trees in the process. You can choose which journal. There are several that you’d want to submit to. Usually you try and submit to a journal that has a what we call a high impact factor, so it’s got a really good reputation.
You submit it to this journal. I submitted it to the Monthly Notices of the Royal Astronomical Society. And then they do this important process called a peer review. They send your paper to somebody else who is an expert in the same field, but who was not an author on your paper.
And they have to read through it and they have to make suggestions and say, okay, yes, this paper looks like it’s scientifically rigorous. This is really well done. All of the analysis is correct. Or they make suggestions for changes. They say, oh look, you’ve actually forgotten to factor in this. Or then they might make some small changes, they might suggest some big changes. And then you get it back and you have a chance to change things. And then you can submit it back to the journal and then it might go through that process again, or it might be accepted.
My paper was accepted in, I think it was December of 2020. And then you have to do some things like you have to make sure it’s all type set to the nice format of the journal and you wait for that to happen.
And then finally it gets published. And often you also put it on the public archive, which is where everybody can access it because some of these journals are closed access. So you actually have to have a subscription to access them. But we obviously want everybody in the world to be able to access science and what we publish. So that’s why we also publish a version of it in the public access area. And that’s the process from start to finish.
Dan: [00:30:09] Thank you. I should point out that that practice of publishing things on what’s called the arXiv, which is a freely available archive of all of the papers, is kind of unique to astronomy.
Jacinta: [00:30:22] Is it?
Dan: [00:30:23] Yeah. Most other sciences and especially medical research and things are behind a paywall. So you can’t access these journals without paying. And that slows the whole process down quite a lot, actually. Whereas in astronomy, often people post on the arXiv things which have been submitted, but actually haven’t been peer reviewed yet. Just to give people an indication of what’s going on and what’s coming.
Particularly if you’re experienced and confident in your work. Are you’re confident it’s going to get published without many changes. You stick it on the arXiv and people can read it that day. You can publish it one day and it’s out there the next. So it’s a really good way for astronomy to move forward quickly and for these discoveries to be shared.
Jacinta: [00:31:08] Yeah, we don’t have to wait for months and months for the journals to publish it.
Dan: [00:31:13] You don’t actually I have to wait for these articles to be formally published. You can read them almost instantly.
And then the last step of the publishing process, which you didn’t mention is once it’s out there, then you start again.
Jacinta: [00:31:27] Well, yeah, I’m avoiding that part.
Dan: [00:31:30] So take a deep breath and do it all again.
Jacinta: [00:31:36] That’s right. I mean, I guess I could mention if you want the next step.
Dan: [00:31:40] What’s coming next? You must have one in the pipeline.
Jacinta: [00:31:43] My bosses are listening to this. So yes, I’ve been working very hard. Yeah. So I guess you usually have several projects kind of going on at the same time that you’re working on. But I’ve got several ideas of where to go from here with regards to these giant radio galaxies. I’ve put in a proposal to observe them again with MeerKAT, but at a different frequency, at a lower frequency.
And this is going to give us information about the actual age of the electrons in different parts of the jets. So what we think is that we’re going to find that they’re very young towards the center and very old towards the outside. But we are actually trying to find out whether these galaxies are restarted, meaning that the black hole kind of switched off for a while and stopped forming jets.
The old jets kind of kept expanding outwards and then suddenly it switched on again so that you’ve got these new little inner jets and this would indicate restarted activity. Which means that the supply of gas or whatever is falling into black hole, stopped for a while, and then started again, this is going to give us a lot more clues about what’s going on.
So I’m waiting to hear whether or not my observing proposal was successful. So I submitted this application to MeerKAT. Then there’s a time allocation committee who are going to assess it. Lots of people are applying for time, so it’s very competitive. So I may not get this time, this round, but there’ll be another opportunity later to try again.
This is one idea, but another thing I can do is go and look through the rest of the MIGHTEE data. Some of it has been taken in other areas of the sky as I mentioned, it’ll be 20 square degrees in full. And so some of that data already exists. So I can go and check that out. Go galaxy hunting, and see if I can spot some more giant radio galaxies.
Dan: [00:33:23] Awesome.
Jacinta: [00:33:24] And they should be there, right? If we’re right that there are two of these in each square degree of the sky, we should be able to find, I mean, there should be 40 in the entire MIGHTEE region. So fingers crossed we find some.
Dan: [00:33:36] I bet you there aren’t. And then you’re going to have to rethink the whole thing again.
Jacinta: [00:33:40] No, Dan don’t say that! But actually that could be more interesting to be like, what on Earth is going on in this particular part of the sky?
Dan: [00:33:49] Yeah. That’s the fun. You never really know what you’re going to get.
Jacinta: [00:33:52] Yeah, exactly. And so that’s a risk, right? You might start a project and it could go nowhere because you don’t know what the answer is.
That’s the point of science is that you’re doing something that no one else has done before, but it could also be a really cool discovery.
Dan: [00:34:05] Great so I think that’s it for today.
Jacinta: [00:34:08] Yeah. So thank you for having me as a guest. It was a weird experience. You could hear how nervous I was.
Dan: [00:34:16] That was great. I mean, we’ve been wanting to talk about your research for a while and you’ve kind of been holding it close to your chest because there is something about that.
This research and endeavor, you don’t want to get scooped either. You don’t want somebody else to see your idea before you’ve published it and then publish it themselves. Because that does happen too. So you do kind of hold these things a little bit close to your chest. Mostly it’s a kind of nice environment, but it’s rare.
Jacinta: [00:34:44] Mostly people are really nice and cool about that, but it can happen.
But, anyway, I wanted to time this with the release of the official publication of the article, of the paper, and also the press release. I wrote a little press release and I’ve sent it out to various places. And so if anyone wants to contact me to talk about it, you can.
Dan: [00:35:01] Yeah. Let’s, let’s hope it gets picked up. You know, it’s a pretty cool discovery and well done.
Jacinta: [00:35:07] Thank you.
Dan: [00:35:08] And thank you very much for listening. We hope you’ll join us again for the next episode of The Cosmic Savannah.
Jacinta: [00:35:13] You can visit our website, thecosmicsavannah.com, where we’ll have the transcript, links to other stuff related to today’s episode.
And you can follow us on Twitter, Facebook, and Instagram @cosmicsavannah that’s Savannah spelled S a v a n n a h.
Dan: [00:35:29] Special thanks today to Dr. Jacinta Delhaize for speaking with us.
Jacinta: [00:35:34] Thanks to our social media manager Sumari Hattingh, and all The Cosmic Savannah volunteers. Also to Mark Allnut for music production, Janas Brink and Michal Lyzcek for photography and Lana Ceraj for graphic design.
Dan: [00:35:47] We gratefully acknowledged 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.
Jacinta: [00:35:57] You can subscribe on Apple podcasts, Spotify, or wherever you get your podcasts. And if you’d like to help us out, please do rate and review us and recommended us to a friend.
We’d really appreciate it.
Dan: [00:36:07] And we’ll speak to you next time on The Cosmic Savannah.
Jacinta: [00:36:19] This is really good practice for me. It’s hilarious how, like, ah, I’m nervous and I’m stumbling and it’ll be good for like radio interviews to practice this stuff.