On 22 December, the James Webb Space Telescope (JWST) is set to launch. The 6.5 wide telescope is an infrared observatory capable of looking at the cosmos from our neighbouring planets to the farthest depths of space where we are just receiving the light from the first galaxies. We look over what the telescope is, its difficult journey to the launch pad, and what it hopes to achieve once it reaches orbit.


Ezzy Greetings listeners. It's time for the January episode. I'm news editor Ezzy Pearson and I'm joined on the podcast today by editor Chris Bramley.

Chris Hello.

Ezzy Coming up later today, we'll be telling you how you can see Orion in our stargazing tip of the month. But first, we're going to take a moment to talk about our January issue, which just so happens to also be our 200th issue. So we're all very proud that we've been going for, what? Is it 16 years?

Chris The Sky at Night magazine launched with the June issue 2005. Way back 16 years ago. And yeah, what? What a what a time. It's been 200 issues, and I'm very pleased that we've been able in the 200th issue to include a double page spread on which we have every single one of our covers and right back to the very first issue, which is in which it's just a mind boggling sight. Personally speaking, when he looked back on it saying all those issues that we've we've created together. When did you join the magazine Ezzy?

Ezzy I joined, funnily enough, back on issue 100. That was the issue that was going on sale when I started. So for me, it's been particularly poignant. It's my 100th issue. That's amazing, which is, you know, it's it's great to have been able to sort of be on the forefront of all of these observations and scientific discoveries that's been happening because one of the things that we did in the issue was we had Chris Lintott, who's one of the presenters of The Sky at Night, write about all of the scientific, the biggest scientific discoveries that have happened over the years and years that the magazine has been going. And some of them were really sort ... you feel have been around for longer than 16 years. Like, for instance, back when the magazine started, we barely knew of any exoplanets. Now we know thousands and thousands and we're beginning to get close views of them and understand what their climates are like and what they're made up of. And so that was kind of, you know, a really interesting shift to see.

Chris The advances there have been incredible, haven't they?

Ezzy Yeah, yeah, exactly. We've we detected gravitational waves for the first time in detected, but hadn't even been built.

Chris It's a whole new chapter of astronomy, that isn't it? That's just started in the in the past 15 years. Absolutely incredible. And I mean, personally... You say issue 100. I've been on Sky at Night magazine since Issue 1, Not as Editor, I started out as as the production as the sub editor on issue one. So I can remember quite clearly putting that very first issue together and working on all those, all those issues. And I became the editor in issue 77 back in 2012 and being able to see all the covers just brought back some of the great things that we've covered since then and some of the great things outside the magazine that we've been able to do as well. And things like the total eclipse event that we put on in March 2015 in Bristol. It was a total eclipse in some parts of the world from the UK it was a it was a it was the largest partial eclipse that we'll get to see for many, many years. And it really it really was. I think it was probably about 60 to 65 percent of the Sun was covered by the Moon, from Bristol anyway. And we had we had about we had hundreds of people turn up to the event in the morning, the sky was quite cloudy, but it cleared just at the right time for us to see the the the eclipse. So that was fantastic. The other thing we've done in the issue is we've got in touch with some... We found out that some of us subscribers have been reading the magazine since issue one, an amazing number. Actually, 120 subscribers have been reading the magazine since Issue one, which is just fantastic. And I think, you know, we're so grateful to all our readers for following us for that long. We talked to just five of them and it was so interesting to hear their, you know, their insight into the kind of astronomy they do, what they find interesting about the hobby, what keeps them going. And and it's just a really unique insight into into what people what what gets people going about the hobby and about the science.

Ezzy Yes, it it's absolutely fantastic, and we're thankful to all our readers and hopefully some of our listeners or readers as well. And so if you want to read more about what's been going on in the 200 issues of Sky at Night magazine, the discoveries that have been made, the observations that have happened be sure to pick up up 200th issue. However, there is another landmark occasion that will be happening in mid December, and that's on the 22nd of December the James Webb Space Telescope is finally due to launch.

Chris And finally, yes, after many years

Ezzy I say, finally, because it was first supposed to launch back in 2007, that was its first launch date. It's a bit behind.

Chris Yes, there have been delays. It is a massively complex instrument, and it's going to set the standard for astronomical observations in the way that Hubble did when it first launched.

Ezzy Mm-hmm. And in fact, that's why the JWST, as it's also known, was first envisioned. It was meant to be a follow up to the Hubble Space Telescope, but it's a very different animal. It's an infra-red telescope. That means you can look through the dust in the universe because dust is everywhere. And if you're looking visually, you can't see through it, but infra-red can.

Chris No hoovers in space.

Ezzy No hoovers in space, exactly. And it's got a six and a half metre mirror. And there's a problem when you have a mirror that big, which is that it won't fit in a rocket. Rockets are only about three and a half metres wide. I think that's the maximum width you can fit in that

Chris We can fit and they couldn't fit it in.

Ezzy Could they know they are having to fold the mirror up? It's been constructed out of 18 hexagonal plates, all of which were very gently curved to to create the mirror shape that you need. And they've these are also coated in gold.

Chris That's right. The gold plated on it's very dramatic. It looks very dramatic, doesn't it? All these different segments are hexagonal, too, so it looks a little bit like a kind of bee... Honeycomb, doesn't it? It does.

Ezzy It very much looks like a beehive or a honeycomb. And the reason why is gold rather than the usual silver, these is because gold reflects infra-red light much more effectively and much better good.

Chris That gold is a very is a very thin, micron thick, thin plating, the vast proportion, the backing of behind that gold-plating is beryllium, which is a very, very rare metal, isn't it? And actually of it doing some, some reading up on beryllium. It's an absolute. It's an absolutely fascinating element in terms of the particle physics, Ezzy isn't it? I mean, I did. I had no idea how it was, how it was formed and all elements heavier than than iron. All the elements are formed in stars, aren't they? That's, you know, it fused, fused together from hydrogen and helium.

Ezzy All the ones up to iron anyway.

Chris Up to iron. But you can't get any heavier elements than that formed within a star and every element in the periodic table. Heavier than iron is formed in a supernova, but not beryllium. I just it just I just find it absolutely mind boggling that it takes a supernova to form these have heavy elements. And then and then some of these heavy elements are struck by cosmic rays just randomly struck by cosmic rays. And then and then that go up... That and that reaction goes on. And some of those some of those elements that are formed from these cosmic rays strikes and go on to create beryllium, which is which is just the mind boggling, the kind of chances of this happening throughout the universe over time. To create the metal... kind of explains why it's so rare, I guess.

Ezzy Yeah. So it is this incredibly rare metal, but it's also very light. It's number four on the periodic table, which means it's an incredibly lightweight metal, which is great if you're trying to build your spacecraft out of it. But it's also still strong. It's got all of the other properties that you want to have if you're you're making a mirror. And so that's why they sought out this incredibly rare metal to make these 18 hexagons out of.

Chris That's right. That's right. Yeah. And it's going to have quite a lot of instruments on board. Isn't it Ezzy.

Ezzy There are four main instruments. There's a near infra-red camera, a near infrared spectrometer, a mid-infrared instrument as it's called, or MIRI and a near-infrared imager and what's called a slitless spectrograph. So a spectrograph gets in the light from distant stars or distant objects and then sort of splits it up. That allows you to... when you've got that sort of spectrum, you can see all of the different what's called spectral lines. So these are when you've got a certain element in a star, it glows with a certain colour of light and you can pick out that colour of light and be able to tell that element is in a star. And so you can begin to pick out what you know... I say star. It could be an exoplanet. It could be something around a distant planet. We'll get more into what JWST is actually looking at later, but it's got this entire suite of instruments that are going to be able to just really break apart what these planets, what these cosmic objects are like and look at things that we just haven't had the capability to do before because this is the first big... We have had infra-red telescopes before, but it's hard to put one on Earth because Earth's atmosphere just soaks up all of the infra-red and all you end up seeing is the Earth's atmosphere. So you need to put it above the Earth's atmosphere. And there has been various telescopes. They've been much smaller because they haven't had this massive 6.5 metre mirror, and they've also tended to be very focused on a specific part of the spectrum looking at a specific thing. So things like Herschel and Spitzer, things like that, they were very sort of focussed on on a narrow range of things to be able to do, whereas the whole point of the JWST is it's just going to be this kind of broad approach, looking at all of these different things and just basically people can come up with whatever observations they want to do and apply for time. And I say that'll get it, but it's incredibly in-demand instrument.

Chris The time the time is is is precious on on JWST, isn't it more so than Hubble? When you look at how broad the part of the spectrum is that the Webb telescope will be able to see. It's hugely wide. It covers over half of the of the of the spectrum towards the infra-red and which of the longer wavelengths of light. Of course, one of the things that helps the Webb telescope to be able to take such good observations to be able to see so much of the infra-red part of the spectrum is the fact that it's going to be just a huge distance from Earth. Hubble orbited the Earth five 570 kilometres above the surface. The Webb telescope is... It's not even going to be orbiting the Earth. It's it's launching on this huge Ariane 5 rocket from French Guiana from Spaceport Europe. ESA's spaceport in French Guiana, which is in South America. It's going to travel one and a half million kilometres away into deep space, and there it's going to be. It's going to travel to a point in space known as the Earth Sun Lagrange Point L2. Now there are four of these Lagrange points around Earth. And at these Lagrange points, the gravitational forces of the Sun and Earth exactly balance the centrifugal force, acting to carry objects further out into space. So in effect, objects at these Lagrange points hover the kind of stationary position in relation to the southern Earth without having to expend much fuel. Now the there are four.... I said there are four of these there. Two of them are on the orbital path of Earth ahead of and behind the planet. Our planet on its orbital path. One is in between the Sun and the Earth. And before the second one L2, where JWST is going, is on the far side of Earth from the Sun. And there is going to be far, far away from all there, all the light from the Earth, the Sun and the Moon, which will keep instruments cool. And the other thing that JWST has built into it is this huge sun shield, which is going to block even more of the light from the Sun Moon and keep its instruments incredibly cool, which is vital for taking Infra-Red observations. I mean, it just it's just it's just a different beast to Hubble. It really is. You know, as well as orbiting at a vastly greater distance from from our planet, it's going to it's got this 21 metre wide sunshield. It's about the size of a tennis court, if you can picture that in your mind.

Ezzy Absolutely huge.

Chris Whereas Hubble was 13 metres in length about, you know, about the size of a of a coach or a school bus. We've already talked about the mirror, and the mirror is going to be six and a half metres in diameter, whereas Hubble's mirror was two and a half, 2.4 metres in diameter. And so that that gives the Webb telescope over six times the collecting area of the Hubble Mirror, which is going to mean it collects more light and it's going to be it's going to be giving astronomers much greater resolution in terms of the observations that it can take. It's going to be able to see much finer detail. One interesting thing that I noticed was the difference in mass between the two instruments. Do you know anything about that Ezzy which which do you think is the heavier

Ezzy That is one of the kind of measurements I haven't actually looked at?

Chris Hmm. It's fascinating because I was expecting, you know, so much in terms of its size. It's a much bigger instrument. In actual fact, the Webb telescope is half the mass of the Hubble Space Telescope. Hubble Space Telescope comes in at 12 tons. Webb Telescope weighs six and a half tons.

Ezzy I mean, that's what you get for making your plates of beryllium.

Chris That's what you get. Yeah, that's right. That's right.

Ezzy But I don't I don't know if any of our listeners at home have ever seen pictures. Those on the NASA website, they have lots of them where you can see sort of this absolutely enormous telescope next to the people who are working on it. And it gives you this kind of sense of scale of just how big it is. But it's, you know, as you said, it's the size of a tennis court with this massive thing sticking up the side and as high as a house.

Chris This giant thing. And it's going to be launching on December the 22nd, isn't it? We do wish it well.

Ezzy Hopefully, we'll be launching on December the 22nd because it has had a bit of a past and a bit of a history on the way to the launch pad. As I said, it began development back in 1996, meant to be a successor to Hubble, but a complementary one. Initially, its forecast what was forecast to cost around about $500 million. I think at the end tally, it's more like $10 billion. That's a that's a bit of an increase in cost that.

Chris That is quite that's quite an increase, isn't it? Yeah.

Ezzy But it was originally supposed to launch in 2007, but it had a major redesign in 2005, at which point it was the launch date was pushed way back. It was going to be much more capable of what it could do and much more advanced.

Chris That's right.

Ezzy So basically, it been suffering from scope creep up until that point where basically everybody said, it's like, Oh, why? Why do we put this on? Why don't we make it do this? And in 2005, they sat down and said, OK, let's see what we can actually put on and go with that. The main construction finally finished in 2016, at which point it was going through testing. And this is where things really started going wrong because in March 2018, they were practising deploying this absolutely massive sun shield. But there's one very small problem with a sun shield that is the size of a tennis court, but has the thickness of 0.05mm. It's incredibly thin and there's five of these sheets and they all have to go out perfectly. And during this test deployment, it tore and there was no way to kind of repair this other than sort of completely taking that layer off and putting it back on again. Mm-Hmm. Mm-Hmm. So that took another couple of years, and the launch date was suspended back again. And then in March 2020, the pandemic happened and they had to push back the launch date again to the 31st of October because basically, NASA decided that they really needed to sort of concentrate their resources that they had. On things that were needed to go at a certain time. So, for instance, they were working on the Perseverance rover that had to be ready by, oh, when did that launch in August? Because otherwise it was going to miss its launch window. Whereas JWST can launch pretty much at any time

Chris it can launch anytime. is not critical. Is that because it's not having to kind of tie in with the orbital path of different planets? And it's quite the scheduling. You talk about kind of scheduling trains, scheduling stuff in terms of orbital dynamics, and those set and the motion of the planets is a is an order of magnitude more tricky than National Rail, isn't it?

Ezzy Yeah, exactly. So then it got pushed back to the thirty first of October. Then in August, all it'd be all the Ariane five rockets, which is what the JWST will be flying on, were grounded because there was an issue with that their payload fairing. So that's basically the kind of the panels that go around your instrument to protect it during launch. So it got pushed back three months to the 18th December and then a couple of weeks ago for us, about a month when this comes out, In late November, something called a clamp band released whilst they were mounting this telescope on top of the rocket and shook the entire telescope. And it must have been. So you know, you've got this half billion telescope...10 billion dollar telescope that people have been waiting decades for. So people have been going on and on about making jokes about how delayed it is. And then you just suddenly see the entire thing go [shaking noise].

Chris Yeah. And one little... when you say clamp band I'm imagining a kind of rubber band just pinging off air and flying off into the corner or some clean room.

Ezzy I think that is basically what happened. But fortunately, you know, the telescope was going to suffer much worse shaking during launch. So it was they put in an extra couple of delay,... Couple of days delay just to, you know, check everything thoroughly and make sure everything was OK. Yes. And finally, on the 22nd of December, that is when it is due to launch. Finally.

Chris Well, I think it's just as well that they're doing all these checks ahead of time and taking in and putting in these putting in these slight delays because of course, being that far away one and a half million kilometres out in space, you know, we can't service it in the same way that Hubble was able to be service absolutely teams of astronauts. It's going to be out there. It's going to it has to, you know, there is no leeway for repair once it's out there. So we need, you know, all the all the kind of the the global consortium of space agencies who are who are who are creating this, this amazing mission. They all are invested and they all want to make sure that it's absolutely going to work when once it once it launches to space. Mm.

Ezzy Absolutely. And. Unfortunately, one of the... Because you mentioned Hubble again, one of the things that they were hoping they'll be able to do was have JWST and Hubble making observations at the same time of the same thing so you could they could work together? Yes. And because of all of these delays, unfortunately now Hubble is not doing very well. It's constantly going into safe mode at the moment. Sort of every couple of months, I get a report instead of saying Hubble is going back into safe mode and most of the time they can, you know, flick a couple of switches, turn off and on again, and it works and it's fine.

Chris They can do some software updates, can't they, on this thing...

Ezzy There's no space shuttle anymore, so they can't go and service it. So hopefully they'll be able to get at least a couple of months out of the two of them working together. I think they're hoping for a couple of years, but we'll have to see if that happens. But it is. It is an exciting time because even by itself, the JWST, as we said, is a huge, incredible instrument. It's going to be able to observe all over the cosmos from our own Solar System back yard right the way out to you know, the earliest solar... the earliest objects that are out there.

Ezzy So the what's called the cycle one observations have already been assigned. The first 6000 hours of JWST time has already been assigned. There are small programmes which only are less than twenty five hours to do medium projects, which are twenty five to seventy five, and large projects which are seventy five hours long. And there's there's dozens of these have already been assigned studying exoplanets and their disks around them. So this is going to be one of the big things that its going to be really good up because it can can look through the dust. It looks in the infra-red. It can see these hot young systems seeing them as they grow and really begin to sort of pick apart what's called the protoplanetary disks. So this is the disk of dust and debris that's around planets. And pick out possibly even, you know, growing planets, perhaps even some growing moons, which is something we're beginning to hear about in these disks of dust. Equally, it will be looking at really early galaxies seeing how these grow again, they tend to be quite dusty. So being able to see in that part of the spectrum are really helping this. Yeah.

Chris And yes, talking talking about the first galaxies, we're talking about looking back in time to a very, very early period of the Universe's history. The first galaxies formed around 300 million years after the Big Bang. And Hubble was able to see the kind of later stages of that of that period in the universe's history. JWST will be able to see much farther back into that period. And in fact, it will be able to see beyond that further back into time again. Back to when the first stars were being formed. And that really is something something incredible to be able to see the very first generation, the very first population of stars and how they were formed. And it's going to be fascinating to see how they're different from stars. Later stars are formed these days.

Ezzy Yeah, it's it's really looking into a lot of this kind of like a very early, very distant galaxy. Because, again, it can look through the dust that fills the Universe and get a much clearer picture of what's going on. So looking at things like the the intergalactic medium, which is the the stuff between galaxies is sort of vague, like not even clouds, just this sort of wash of stuff.

Chris The very tenuous stuff, the very tenuous, almost it's it's almost a vacuum, isn't it? I mean, there's probably about one atom or one particle of matter in a huge, huge volume of space isn't there. We're talking in the interplanetary medium. Yes, fascinating. That's going to be able to characterise that characterise that a little bit more. But what's it going to see in the Solar System that a bit closer to Earth?

Ezzy So this is actually really very interesting. The Hubble Space Telescope is going to be looking at lots of the outer planets Jupiter, Saturn, Uranus, Neptune. It won't be able to look inwards, unfortunately, because they're too close to the Sun.

Chris Too much light, too much heat.

Ezzy You've got this massive telescope that they are. They've built a tennis court sunshield to protect it from the light of not just from the heat of not just the Sun, but the Earth and even the Moon, which is so bright, you know.

Chris Event he reflected light from these bodies is too much for it to look at.

Ezzy So to get to be able to look at, but that means it's going to be looking at these gas giant planets, which is going to be really fascinating because infra-red is really good for looking down into planet atmospheres. So if you've got these thick atmospheres like Jupiter, Saturn, Uranus, Neptune, they all do. That's what it's going to be able to start picking apart. It's going to be able to see some of these layers.

Chris That's one of the things that excites me. I, I find and one of the one of the branches of astronomy that I'm I'm particularly interested in is planetary science and particularly in planetary science is the is these gas giants, what is under the visible surface of Jupiter? What is it like? What is under the visible surface of Saturn? It's just, you know, that kind of thing is I'm just so curious about that. And it's just I'm, you know, I'm in an really keen anticipation of what we'll find out.

Ezzy Yeah, it's whenever because quite often you when you look at these planets, you realise they've got these layers where they have very romantic sounding things going on like it rains diamonds and sapphires. The winds blow with rubies, and then you actually think about what that would be like. And it's horrific.

Chris Yeah, pretty bad. You have a pretty strong umbrella. Yeah. Take on a visit that place me. Yes. But interestingly, Uranus, Uranus and Neptune are interesting targets as well. I'm really pleased that there has been some observation time allotted to to the to those ice giants because we have such a low resolution view of them. Really don't believe that the only observations we have of them close up are thanks to the Voyager flybys in the late 1980s. And you know, that's that's three decades ago. You know, the kind of distant past nowadays in terms of the kind of technology and the capability of instruments. So yeah, I guess it's time that we discovered, you know, we did some put in some more time observing those worlds.

Ezzy Yeah, because the planets you again have the problem of the Earth's atmosphere. But this time it's not just like removing the light like it does with infra-red, it's moving the light. So as it comes through, the atmosphere has a bit of a wobble to it, something called seeing it. And that blurs the image of these distant planets, which is why Hubble did spend some time looking at that at Uranus and Neptune, but it only had a 2.5 metre mirror. It could still only detect so much on these planets. And even though that was a project that sort of looked at extended periods of time, which I think the JWST is going to carry on, it's not just sort of taking like one snapshot of these planets and then moving on and never returning. It's going to sort of take different pictures at different times and sort of keep track of the planets as they move on. And that's again, that's one of those things. If we can get Hubble doing that at the same time in the visual light – because it always does have some visual capability, but it's not its strong suit. It's it's it's much more of an infra-red thing. So if we can get those two together for a bit, that's going to be some really interesting results and some stuff that because that's one of the things with the things that these big telescopes do is it's not necessarily just going and doing this one observation. And that's done and that's that one project that's going on. It's creating this entire legacy of data that's open to everybody. It's the NASA instrument, and NASA has this policy that any data that the instruments takes will be open to everybody.

Chris Now it's time for the stargazing tip of the month. The winter skies see the return of one of the most recognisable constellations, Orion the Hunter, the bright stars of Orion make it easy to find and are a great opportunity to teach younger astronomers about how to navigate the sky. First, locate the three bright stars in a row that form Orion's Belt, you should then be able to see the four stars that marked the corners of a rectangle around the belt. The top two stars are called Bellatrix and Betelgeuse, marking Orion's shoulders. The bottom two stars are named Saiph and Rigel and mark his feet. Orion offers an easy way to see the difference in colours between stars Rigel on the bottom right of the Constellation is blue, white and colour, while Betelgeuse on the top left is a distinct reddish orange. This is because Betelgeuse is an older star heading towards the end of its life. It's run out of fuel and enter the red giant phase, where its outer layers cool and glow red. Meanwhile, Rigel is a massive star. Burning is fuel very rapidly, getting white hot. If you fancy more of a challenge, then try to locate a line of stars hanging down off Orion's belt. This is the Hunter's sword. Halfway down this sword, you may see that one of the stars looks a bit fuzzier than the rest. This is the Orion Nebula, also known as M42. If you have a pair of binoculars or a small telescope to hand, you should be able to see even more detail in this region. Though bear in mind, it won't look quite like the images you might have seen in the pages of Sky at Night magazine. Like all nebulae, these colours can only be pulled out by extensive image processing. To the eye M42 looks like a pale, misty cloud. But don't let that put you off. There's nothing quite like being able to see a distant nebula with your own eyes.

Ezzy So that's it from us this month. Be sure to pick up our 200th issue of BBC Sky at Night magazine, where we also hear from readers who have been with the magazine since Issue 1, look back over the greatest scientific breakthroughs and landmark astronomical events that have occurred in the last 200 issues and preview the biggest missions and observing events to come in 2022. And that's not forgetting our regular sections that will help you unlock the wonders of the night sky, find the right equipment to observe it with, and discover the best things to see after dark this month from all of us here at BBC Sky at Night Magazine. Goodbye.


Elizabeth Pearson
Ezzy PearsonScience journalist

Ezzy Pearson is the Features Editor of BBC Sky at Night Magazine. Her first book about the history of robotic planetary landers is out now from The History Press.