University Place

Why We Need the James Webb Space Telescope

– Welcome to this presentation from UW Space Place. I’m Jim Lattis, the director of UW Space Place, which is the education and public outreach facility of the University of Wisconsin-Madison Department of Astronomy. Today, our presenter is Professor Michael Maseda of the astronomy department of UW-Madison. Professor Maseda, before coming to Madison, was at the Leiden Observatory in the Netherlands. And before that, earned his PhD at the Max Planck Institute in Germany. Today, Professor Maseda is on the Science Team of the James Webb Space Telescope, and so is highly qualified to tell us today why we need the James Webb Space Telescope. I hope you enjoy his presentation.

– Thank you, Jim. For more than 30 years, the Hubble Space Telescope has been one of the primary tools that we astronomers have used to study and to understand our universe. And it’s been so successful that we’re actually doing science with it that we couldn’t have even imagined before the mission began.

We’re answering questions that we didn’t even know that we had. And it’s been so successful in so many different areas of astronomy, in part, because it offers really unique capabilities that only a large, space-based telescope can provide. It’s very dark in space, so you’re able to get very good pictures of things. You don’t have to look through the Earth’s atmosphere, which tends to make images very blurry. And so it’s been this fantastic mission that we’ve used to understand the universe. And we’ve gone from studying things, for example, on the moon, taking fantastic, really crisp, sharp pictures of craters in the moon. Learning more about how impacts there work. Inside the solar system, we can study other planets and their moons as well, like this picture of Jupiter. With this really fantastic resolution, you can see all of the storms in the atmosphere, all of the clouds, and really learn a lot more about how our neighbors in the solar system look. On larger scales as well, and this is one of the really most iconic pictures that we have from the mission.

These are the Pillars of Creation, and these are actually star nurseries. Stars and planets are being born inside these massive columns of gas. Now, you can’t see them directly; they’re sort of inside the clouds themselves, but you can see a little bit of the light kind of peeking out, a little hint of what’s actually happening deep inside these regions. We can also learn more about what happens after stars die. This is the Crab Nebula. This is the remnant of a supernova that happened about a thousand years ago. In fact, it was so bright when the star exploded that it could be seen during the day on Earth. But we had no idea at the time what that actually was, and we couldn’t have even imagined taking a picture like this, where you can actually see the ejecta, the things that’s been expelled from the star as it has exploded. So the star used to be there in the center, and now we have these clouds of gas expanding outwards from it. And, of course, this is arguably the most iconic picture from the Hubble Space Telescope.

This is the Hubble Ultra Deep Field. And it’s with pictures like this that have actually completely changed our view of the universe. It’s changed our conception about how large the universe is and how many galaxies there actually are in the universe. Some of the most distant galaxies that we actually know of are contained inside this image. And that’s very important because light travels at a fixed speed. And so, the further away something is from us, the longer it’s taken that light to reach us. So the most distant galaxies, that light’s been traveling for billions of years before it can reach us. And so we’re able to look, essentially, at pictures of what the universe was like at very, very early times. And as important and as instrumental as Hubble has been in our understanding of the early phases of the universe, Hubble hasn’t been able to answer all of our questions. We still don’t know when the first galaxies formed.

When the first stars in those galaxies formed in the history of the universe. So we’re missing the crucial first chapters of how our universe came to be the way that it is. And so, that’s been a motivation, really, for the better part of the last 20 years for a new telescope to go beyond what Hubble can do. That telescope is called the James Webb Space Telescope or JWST, and it really will unlock a whole new version of the history of the universe, and really tell us a lot more about how everything started. So over the course of this talk, I’m gonna be talking about our own galaxy, which is the Milky Way, how it relates to other galaxies. I’m gonna talk about how we can actually study other galaxies in the universe using, for example, the Hubble Space Telescope. We’ll talk a little bit about physics. I’ll talk a little bit about light and a concept called redshift. I promise we’re not gonna have any equations. And how we use telescopes to find extremely distant galaxies.

Then we’re gonna go through a checklist of the things that we will need for the next telescope to help us understand what’s happening at the very, very earliest times in the universe. That telescope being JWST. I’ll talk a little bit more about that, how it was developed, and what we’re actually planning on using it for. Now, if you live somewhere where it’s really dark at night and you go outside, or if you’ve visited anywhere very dark, on a cloudless night, you’ve probably been greeted by a view that looks a little bit like this one. This is the Milky Way, and this is our galaxy. Our sun is one of a few hundred billion stars inside the Milky Way galaxy, and it’s shaped kind of like a disc or a pancake. And so, when you’re actually looking through the disc is when you can see all of the stars. You can see the glow from these billions of stars in our galaxy. So we live sort of two-thirds of the way out. And when you’re looking through the disc, you can see, in this case, to the upper right is sort of bluer, to the lower left is sort of redder, and the lower left in this image is actually the very center of the galaxy.

Now, I said this is what it looks like on a cloudless night, but you might be able to see some clouds in this image. Those actually aren’t in the Earth’s atmosphere. Those are massive clouds of gas and dust actually in the galaxy itself. And so, the reason that you see bluer versions up into the upper right, and redder images into the lower left, part of that is because of the dust. So when you’re looking towards the center of the galaxy, you’re going through a larger column of dust that makes things look a little bit redder, but also, younger stars appear more blue in color than older stars, which appear a bit more red. And so, you can see this gradient is showing you that slightly different ages of stars live in different parts of the galaxy. Now, in the very center of the galaxy, in that lower left hand corner, we actually know that there’s a supermassive black hole. This is a black hole that’s so large there’s a gravitational pull that can suck in all of the things around it, all of the gas and stars even around it. Now, it’s far enough away from us that we don’t have to worry about it, but it’s really cool that we have a massive black hole in the center. And in fact, all of these properties of our galaxy took us a long time to figure out.

It’s actually very difficult to discover what kind of thing you’re living in when you’re deep inside it. So, really wasn’t until the 20th century that we learned what a galaxy was, and that this galaxy, the Milky Way, has many, many stars that are a lot like our sun. And I think it’s part of human nature to think that our galaxy must be special or unique in some way. And actually, our galaxy is really average in just about all of the properties that I talked about. In terms of the number of stars, in terms of its shape, in terms of having these big dust clouds, in terms of having the massive black hole, these are things that are pretty common in galaxies. And the reason that we know that is ’cause we’ve spent a lot of time looking at other galaxies and trying to understand what their properties are and seeing that they do, in fact, share many of the same properties as our galaxy. Now, this is a very difficult thing to do because the distances between galaxies are huge. So our nearest major neighbor in the universe is the Andromeda galaxy. And Andromeda is about 200 trillion times further away from us than our sun is. So the distances between galaxies are very, very large.

So they’re gonna look very small and they’re gonna be quite faint. So we have to spend a lot of time looking for them in order to see what they’re like, understand them, and then put the picture together of how our Milky Way fits into the whole picture of what’s going on in the universe. So if you want to find another galaxy, the best way to do it is to have a big telescope, for example, the Hubble Space Telescope, and you probably don’t wanna be pointing your telescope straight through the plane of the Milky Way. So all of the stars, all of the gas, is just gonna get in the way. So you would wanna point your telescope in a completely different direction and hope that you might be able to see something that’s actually outside of our galaxy. Now, I’m showing you here an image that you probably are all familiar with. This is the Big Dipper. This is in the Northern Hemisphere, about 90 degrees perpendicular to the plane of the disc of the Milky Way. So this would be a great place to look if you’re trying to find other galaxies. Now, I’m gonna zoom in on this region here.

And let’s say that you have a small telescope in your backyard. Even if you live in a city, you could probably use that telescope to see a few more stars that you wouldn’t be able to see just with your eyes. There are still these stars in here. And even if you’re looking perpendicular to the disc, you still see some stars because the disc itself is thick. There’s some three-dimensional structure to it. We’re living inside, and so, there are stars all around us in three dimensions. Now, if you had a larger telescope and you were living somewhere maybe a little bit darker, or you took a very long image, instead of just looking through the eyepiece, you might be able to see an image that looks like this one. So all these stars that you see were there. They’ve always been there. You just can’t see them if you don’t have a large telescope or if you’re not looking for long enough.

So telescopes collect light. And so if you take a longer, longer, longer exposure, you can see the light coming from fainter sources. So if you’ve ever done any night photography, you’ll all understand what that means. So this region here that I’m highlighting now, this little staircase shape, this is where we decided to point the Hubble Space Telescope to look for the most distant galaxies in the universe. So you can see here, right, with any telescope that you’re gonna have, it’s pretty empty. This is a pretty empty part of the sky, pretty dark, seems like a good place to look for other galaxies. And so, the idea was you take the Hubble Space Telescope and you look for a long time. You collect as much light as you can to see if there are any really faint and really distant sources in that area. Now, just for reference, the size of that region is here compared to the size of the full moon. It’s really, really small.

Hubble is not good at taking very, very large area pictures. It’s very good at taking really exquisitely detailed pictures of very, very small regions. So you can only look at a region that’s this big at one time with the Hubble Space Telescope. Now, after it was initially launched, there was actually a major problem. So it was discovered that all of the pictures that Hubble was taking were blurry. The idea was that you have this perfect telescope taking blurry pictures, that’s not really a particularly useful thing to have. So astronauts actually went up and they, as they say, gave it a pair of glasses. So they repaired the system, they added some optical systems to make the images go from what you can see on the left, the blurry ones, to the sharp, crisp ones that should have always been expected that you could see on the right. Now, at the time, this was a big, sort of public relations problem because this is a NASA mission, taxpayer funded, extremely expensive, and it didn’t work. So even though it was repaired, there was a lot of risk, essentially in the mission continuing.

And the director of the Space Telescope Science Institute at the time, who operates the Hubble Space Telescope, was a man named Bob Williams, and he decided to really push it to the extreme. He wanted to look at that one part of the sky for as long as possible with the Hubble Space Telescope, to see what we could find. To see if we could find extremely faint and extremely distant galaxies. So he spent a total of 10 days’ worth of time pointing the telescope at this one part of the sky. Now, a lot of people thought this was a really bad idea, given that it hadn’t worked, given the mission was really in a critical state, spending 10 days’ worth of time, and, of course, time is money. Spending that much time looking at something where the image could come back blank and empty wasn’t considered to be a really wise move. But nevertheless, this happened. And, of course, if I’m talking about it, it was because this whole thing was a massive success because the image that came out is this one here. It’s called the Hubble Deep Field. And this completely changed our view of the universe.

Nearly everything that you see in this image is a distant galaxy. In fact, there are more than 3,000 galaxies in this one tiny part of the sky alone. Now, this is a two-dimensional image, of course, but these galaxies are at all different distances with respect to us. They’re just projected into this two-dimensional space. So some are much, much further away than others. And in particular, we found that there were galaxies in this image that were much more distant and hence, much earlier in time than we ever expected. Now, this maybe was a coincidence. Maybe we just got really lucky and pointed the telescope at a part of the sky that was really different than everything else. So scientists, typically, like to repeat experiments. They point it in the Southern Hemisphere.

So basically, in the complete opposite direction, took the picture called the Hubble Deep Field South, and the same general picture emerges. Nearly everything that you see in this image is a distant galaxy. And so, really, if you have something like the Hubble Space Telescope, and you’re capable of seeing really faint, really distant objects, you’re going to see them. Galaxies are everywhere in the universe at all different distances. Now, over the years, we’ve improved Hubble quite a bit. We’ve gotten new cameras that are more sensitive. We’ve gotten cameras that are sensitive to different wavelengths of light. They now have a sort of rectangular field of view instead of that staircase shape. And the sort of culmination of all of this is this image which we call the Hubble Ultra Deep Field. So everything about this picture is better than the Hubble Deep Field that I showed you before.

It’s much more sensitive, better angular resolution. You could see fainter galaxies. In fact, the only thing that hasn’t improved is the creativity of astronomers in coming up with the name. Because, what’s deeper than deep, it’s ultra-deep, of course. But this is the picture that I showed you before. And this is the best picture we have of galaxies in the very, very distant universe. Now, this is the whole field, but it contains really excellent detail on very small scales, and you can’t really do it justice by looking at the whole zoomed out version. So I’m gonna walk you through this image a little bit, zoom in on a few things, and try to explain them to you. So I’m zooming in on one galaxy in particular here, which is a lot like our Milky Way. In fact, we know that our Milky Way is average ’cause we have seen a lot of galaxies that look like this.

So it’s shaped like a disc or a pancake like our Milky Way, and it’s just inclined to be face-on to us. So you can actually see the whole disc. And what you can see is that this galaxy has some spiral structure or some sort of pinwheel structure. And we think our Milky Way does too. So the stars and the gas in this galaxy are shaped a little bit like a pinwheel. Now, you can also see with the spatial resolution that actually, there are these little dots in it. Stars actually form in very, very dense regions. And so there are gonna be these regions that are a little bit brighter. Those are where stars are being born. Over time, they will diffuse outwards and you won’t necessarily see those points anymore.

So this galaxy has very similar properties to our Milky Way in terms of its shape, in terms of the number of stars, total number of stars that it has. And so it’s been really useful to look at these galaxies and understand our Milky Way in a little bit more context. Now, this is a really cool case here where we actually have two galaxies like our Milky Way, two of these spiral galaxies. And they’re actually so close to each other that their mutual gravitational pull is causing them to run into each other. So these two galaxies are in a process called merging. And eventually, over the next few million years, these galaxies are gonna hit each other, their individual stars are going to interact with each other gravitationally, and the end product is going to be a completely new galaxy. And we think that that galaxy is gonna look a little bit like this one. This is what we call an elliptical galaxy. So now, instead of being shaped like a disc, it’s kind of shaped like a ball. You can see that it’s sort of all one color.

All kind of orange. It’s ’cause there aren’t any new stars being born in this galaxy. So after a big merger, you’re gonna form a lot of stars and you’re gonna run out of gas. Gas is the fuel to form new stars. And you’re gonna be left with a galaxy that just sort of passively ages, gets older, and turns a little bit more orange and more red. Now, this galaxy, as I said, is shaped a little bit like a ball, and there’s more density of stars in the center than there is on the outside. And so, as you’re moving out from the center, the galaxy becomes more and more transparent and you can actually see through the galaxy. And that’s what’s really cool about this one in particular, is because at some point, you can actually see another galaxy that’s behind it, peeking through. So you should get the impression from these sorts of images that there’s a huge, three-dimensional structure to the universe. And when we are taking pictures, we’re really just taking this two-dimensional version of it.

There are galaxies at all different distances contained in an image like this one. Now, all the galaxies that I showed you are relatively close to us. Still extremely far, but relatively close. When I talk about studying galaxies that are further away, talking about earlier times in the universe, the typical one looks a little bit more like this one. So you don’t get the same detail. You don’t really have the same idea about what the geometry is, whether it’s more like a disc or more like a ball, but we can still, even from pictures like this, learn how many stars there are in the galaxy. What kinds of properties do those stars have? How old is the galaxy? How many new stars are being born? We can get a lot of detail out from these images. Now, if you take this to the extreme, as I said, we found some of the most distant galaxies that we know of in this image; what do they look like? Well, they’re even smaller. They’re really just a couple pixels across. You could call them smudges if you want.

And in fact, you wouldn’t even be able to see them with your eyes. In fact, in this particular image, I’ve colored the infrared light as red. So this would be completely invisible to you, but this is an extremely distant galaxy that’s only visible in infrared light. I will explain why that is, but it’s really, really exciting that Hubble does have some capabilities in the infrared. It’s enabled us to push back in time, but it’s still not even enough. So we’re gonna start by talking a little bit about physics. I promised that there weren’t gonna be any equations. We’ll keep things qualitative. And I wanna talk about light as a wave. So you’re probably familiar with other kinds of waves, like sound waves or water waves.

Light is also a wave. And if you’ve ever seen an image like this one where you have a prism that’s actually taking white light and separating it out into the colors of the rainbow, what’s actually happening is the prism is separating out light into its different wavelength components. So white light is made up of all of the different colors of light and the prism separates it out by wavelength. Our eyes interpret different wavelengths of light as different colors. So the longest wavelengths of light that our eyes are sensitive to are red light. The shortest wavelengths that we’re capable of seeing are violet. Everything in between is at different wavelengths. Now, the reason why we see these different colors is because that’s where, essentially, most of the light from a star, like our sun, comes out. But there is light at longer wavelengths and at shorter wavelengths than this. So wavelengths that are longer than red are called infrared, and wavelengths that are shorter than violet are called ultraviolet.

And you know if you’ve ever gotten a sunburn that there is ultraviolet radiation. The sun does produce some ultraviolet light, but, again, our eyes have become sensitive to the part of the spectrum where most of the light is coming out. Now, there’s a physical concept when we’re talking about light that’s really important, and I think here is when it’s useful to use an analogy of sound, which is a wave that we’re also very familiar with. So we interpret different wavelengths of sound as different pitches. And there’s a physical effect which you’re probably familiar with called the Doppler Effect. And this has to do when things are producing sound and things are moving. So, let’s say that you have a siren and that siren is producing some sound. If it’s not moving at all, if you’re at any point around it, it’s going to sound the same. But if you put that siren on a fire truck and the fire truck starts to drive, things change. If it’s moving quickly towards you, we hear the pitch go up.

And if it’s moving very quickly away from you, basically, as soon as it passes, the pitch goes down again. So the physical reason for this is that, as the fire truck is approaching you, the waves are getting compressed. They’re getting squished together. Shorter wavelengths, we interpret as higher pitches. And as soon as it’s moving away from you, the wavelengths get stretched out to longer wavelengths, which we interpret as lower pitches. Now, the same thing happens with light. You have to be traveling much faster than a fire truck for this to happen. But if a source is emitting light and it’s moving very quickly towards you, the light is going to be compressed, the wavelengths are going to get shorter, and the object is going to appear bluer. Likewise, if it’s moving very quickly away from you, the light gets stretched out to longer wavelengths and is going to appear redder. That last effect, when it’s moving quickly away from you and things look redder is what we astronomers call redshift.

And redshift is really, really important because we know that the universe is expanding. So people like Hubble and Lemaitre in the early 20th century discovered that the universe is expanding because we started with a big bang. All of the material in the universe was in one place and then there was this initial big bang, and everything started moving away from each other after that, there was this initial explosion. Galaxies started to form well after this period, but, generally speaking, everything is moving away from everything else. And the analogy with this is, let’s say that you have a balloon and you paste little pictures of galaxies on all parts of this balloon and then you start to inflate the balloon. Every single galaxy on the surface of that balloon is going to see every other galaxy moving away from it. So there’s not one galaxy that’s special in this case. Everything is moving away from everything else. And that’s ’cause the balloon itself is what’s expanding. The space between the galaxies is what’s expanding.

And that’s a sort of lower dimensional version of actually what happens in the universe. But generally speaking, because of the big bang, galaxies are moving away from each other. So we view almost every galaxy in the universe as redshifted. And in fact, the more distant an object is from us, the more its light is redshifted. So the more space there is between us and that galaxy, the faster the total expansion is, and the faster the galaxy is going to be moving away from us. So it’s going to be even more redshifted. Now, this is really important because we take pictures, actually, maybe a little bit differently with telescopes than you might with the camera that you have at home. Instead of taking color pictures, every picture we take, for example, with the Hubble Space Telescope, we isolate individual wavelengths of light by using filters. So for example, in this image here, where I show you this color image, or all of the color images that I showed you before, they’re actually made up of individual monochromatic images that are put together. So instead of taking one color picture, we take a picture in blue light, or we take a picture in yellow light, or a picture in green light.

And then afterwards, we combine them all together. Now, the reason that we do this is sort of twofold. The first one is you get a different picture of the galaxy at these different wavelengths. So you can see in the violet and in the blue images, you really only see this sort of ring around the center of the galaxy. And as I said before, younger stars are bluer. And so in fact, when you’re looking at these images, you’re looking at where stars are being born. You’re looking at where the youngest stars are in this galaxy. And as you move to longer wavelengths, these sort of redder colors, you see that the center of the galaxy becomes more prominent. That’s because there’s more dust in the center of the galaxies, and there’s also more old stars. So doing this sort of imaging with filters, it’s kind of like dissecting the galaxy.

And we can learn a lot about what’s physically happening inside the galaxy by doing this. And the other main reason that we do that is because galaxies are redshifted. And so, you can imagine this is a relatively nearby galaxy, but if it were further away from us, its light would be redshifted. And even further away, it would be even more redshifted. And so in that case, the light that we see as blue would actually be coming out at green wavelengths or yellow wavelengths. And longer and longer and longer wavelengths as the galaxy is more and more redshifted. And so the most distant galaxies we expect, essentially, all of the light that’s coming out in these visible wavelengths will be shifted to longer wavelengths into the infrared. So this galaxy would actually be completely invisible to our eyes. We wouldn’t be able to see anything unless we looked only in the infrared. And that’s how you can tell the difference between an object that’s actually small and an object that’s actually far away.

A galaxy that would be nearby, but very, very small, you’d still expect to see red light and green light and blue light. But if the galaxy were extremely far away, you would only expect to see the reddest light. You wouldn’t see anything at shorter wavelengths. So that’s how we can use these images that we’ve taken in all of these different filters and actually find the most distant galaxies. So that one that I showed you before, where you can only see it in infrared light, and Hubble has only a little bit of capability in the infrared, that’s how we know that this galaxy is extremely distant. In fact, it’s so distant from us that the light has taken more than 13 billion years to reach us. And the universe is only about 14 billion years old. So we’re looking at a picture of a galaxy when the universe was only 4% of its current age. And this is really, really incredible because this thing is very small and very, very faint. So it’s taken weeks’ worth of time using the Hubble Space Telescope pointed at this one part of the sky to see even this little speck.

Because the brightness of this object is equivalent to a 100-watt light bulb 6 million miles away. And the size of this image is about the size of your TV screen 2,500 miles away. And even this isn’t enough. Hubble can’t look at longer wavelengths than this. So Hubble can’t see higher redshift galaxies. And if it could, they would be too faint for it to observe. So we’ve gotten to the point where we’ve reached back to about 4% of the age of the universe, and we still don’t know when the first galaxy started to form, and we don’t know what those galaxies looked like. What would we need, then, in a telescope in order to push back further and really understand the very earliest times of the universe? Well, you need something that’s capable of observing extremely faint objects, even fainter than what I was showing you before. Now, you might have some reason to believe that you can just point your telescope to one part of the sky for even longer periods of time and you’d see fainter things. And yeah, that’s true, but ultimately, if you have a bigger telescope as well, you’ll be able to do this more efficiently.

So if you’ve tried to collect rain water, for example, using buckets, the bigger the bucket you have, the more water you can collect. And it’s the same with telescopes. They’re actually kind of like light buckets. And so, essentially, the larger the bucket you have, the more light you can collect. So you want as big of a collecting area as possible. And when we’re talking about telescopes, we’re really talking about how large its mirror is. So most telescopes actually use mirrors to collect the light, to beam it into its cameras and its detectors. Now, you also wanna put your telescope somewhere really dark. You don’t take pictures of the night sky during the day because the sun is so much brighter than everything else. Likewise, you wanna put your telescope as dark of a place as possible at night.

So we put our telescopes in the desert, for example. The ultimate dark place, of course, is space. But you have some familiarity with this if you’ve ever been to a city and looked up at night or been to the countryside and looked up at night, and it’s just fundamentally very different because of what we call light pollution. So you don’t have the ability to see really faint objects when there’s a lot of other sources of light around. So these two pictures are showing you, actually, the same place, actually, before and during a blackout. So before on a sort of normal day, you don’t see very much of the night sky because you have cars and houses and street lights. So maybe you see a few stars, maybe you see the Big Dipper, and that’s about it. But on the right in this particular image, you can see that, essentially, houses at that time were only lit by candles, there were no street lights, and so you can see much, much better. So you can even see in this place, the Milky Way on this particular night. So it’s the same thing.

We wanna put our telescope somewhere dark. We wanna put our telescope in space. I’ve also emphasized the importance of infrared light and infrared astronomy to find these really, really distant galaxies. Now, conceptually, when I’m talking about taking pictures in the infrared, you’re already kind of familiar with this if you’ve ever seen any kind of a thermal image like this one here, showing you a thermal image of a cat. This is, essentially, just a picture at infrared wavelengths. And in fact, a lot of the technological development for infrared photography comes from astronomy. Now, being sensitive to the infrared is really important and, tied into the previous point, you want it to be as dark as possible. Thermal imaging shows you, actually, that when things are hot, things are emitting infrared light. So the hotter regions of this cat actually show up as brighter. So what you would want to do, ideally, is put your telescope somewhere very cold.

Cold temperatures are gonna make sure that you have as little infrared background light as possible to allow you to take the best pictures of the faintest objects. So taking all of these things together has been more than 20 years of development and a joint mission between NASA, the European Space Agency, and the Canadian Space Agency to put together the James Webb Space Telescope, or JWST. And it really was, from the ground up, designed to do exactly this kind of work. Its primary mirror is 21 feet across. It’s three times larger than Hubble’s, so you instantly can collect a lot more light. It’s also optimized to do science imaging and spectroscopy at infrared wavelengths. As I said, Hubble only has a little bit of capabilities. JWST was designed to do this. And we do have some other infrared telescopes. They’re primarily in space.

It turns out the Earth’s atmosphere also absorbs a lot of infrared light. But this is talking about JWST being 20 to even 100 times more powerful than any facility that we’ve ever had. And so, we often talk about a sort of before and an after when it comes to our understanding of the universe from the Hubble Space Telescope. We know so much more now than we did before. It’s going to be the same thing with JWST. It is such a significantly powerful upgrade compared to everything that we’ve had before, that we’re really gonna unlock a lot more of the secrets of the universe. Now, it was launched on December 25th of 2021 by the European Space Agency at their launch facility in French Guiana in South America. This is a picture of the launch. And this is the last picture that we’re going to have of JWST as it was separating off from the spacecraft. This is the sort of bottom of it.

You can see the Earth in the background. And this is the picture when it started its journey out to its final destination in space. This cartoon is showing you the relative sizes of the mirrors between JWST and Hubble with a person for scale. It’s just much larger, as I said, three times larger. It has a hexagonal shape, and we’ll talk about why that’s important a little bit later in terms of being made of these individual segments, but it’s much larger, so it can collect more light. And also, very importantly, the larger the size of the mirror, the sharper the pictures that you’re going to be able to get. Now, from the beginning, JWST was designed for infrared astronomy. Hubble, for the most part, really just observes the same light that our eyes can see, we call visible light, with a little bit of capability in the ultraviolet and a little bit of capability in the infrared. JWST, as I said, completely designed to be an infrared space telescope. So it can see some of the longer wavelengths that we can with our eyes, sort of orange and red, but going much, much longer into the infrared.

Which is particularly useful, as I said, when we’re trying to understand very, very distant universe. So this image here is a comparison of relative power between Hubble and JWST. And this is the Ultra Deep Field that I showed you before. So on the right panel with a zoomed in version, Hubble on the top, JWST on the bottom, you should see significant differences. So the galaxy is a spiral galaxy that’s like our Milky Way, and it’s much, much sharper with JWST. The mirror is larger, so you can get the sharper pictures. And so, the galaxy actually isn’t kind of fuzzy. It really just is, with the higher resolution, you can see that it does have this spiral structure and it does have these really dense regions, these little clumps where stars are forming. But arguably, the most exciting thing to me is what you see in the background. You see a lot more galaxies in the JWST image than you do in the Hubble image.

So even in a place like the Ultra Deep Field where we have discovered the most distant galaxies to date, we really haven’t seen everything. There are still more galaxies in the universe than we’ve been able to see. Now, some of them, as you can see here, are just too faint. So they don’t have enough stars. They’re not emitting enough light. Hubble just can’t see them. JWST can. And importantly, with the infrared wavelengths that it can observe, it can actually see things that are significantly further away. They’re just completely invisible to Hubble. And yet, JWST will be able to find them in very large numbers.

Now, this is not the first infrared space telescope we’ve ever had, but it is, by far, the largest space telescope that we’ve ever had that’s sensitive to infrared light. So you see this progression from left to right of, essentially, the larger mirror size in an infrared telescope, going from 16 inches to about 2. 8 feet to the full 21-feet mirror of JWST. And the images get progressively sharper as you do this. And you can also see, right, those things that look kind of like blobs are actually stars. You couldn’t really tell from these images with the very small telescopes, but with JWST, you can tell they’re stars. And the reason you see that they’re stars is ’cause they have these diffraction spikes. That’s because of the optical design of the telescope and the fact that the mirror is hexagonal. But if you see that pattern, essentially, you’re talking about observing a star where all of the light is concentrated in a very, very small area. What you should also be able to see is there’s a lot of structure in this image as well.

It’s not just stars. You can actually see this sort of faint fuzz around some of the stars, and that’s actually dust. So dust in the galaxy, in our own Milky Way is emitting heat; it’s a little bit warm. And so, you could see it in infrared light. So you can actually see all of the gas and all of the dust between these stars. And you can only see in infrared light, and you can only see when you have very good resolution. So because Hubble is not sensitive to this, you can’t take these sorts of pictures. You’re sensitive to the infrared, sort of heat radiation with JWST. And in fact, it’s so sensitive that you’d be able to, with JWST, see the heat signature of a bumble bee on the Moon. That’s how sensitive that we can actually get down with JWST.

So that all sounds great, but why does it look like that? If you kind of squint, the Hubble Space Telescope looks more or less like a telescope that you might have in your backyard. Sort of shaped like a tube, light comes in one side, you have your cameras and your detectors on the back end of it. JWST looks completely different. There’s this weird apron thing around it. The mirror looks different. These are all for very, very good reasons. The main thing to keep in mind is that JWST is not going to be in the same place as Hubble. Hubble’s orbiting around the Earth. JWST is going to be about a million miles away from Earth, orbiting around the Sun once a year. So it’s orbiting in lockstep with Earth, just a million miles further away.

It’s at a special part of space called L2 or the second Lagrangian point. And this is where the gravitational pull from the Earth and from the Sun are about the same. So you don’t have to use very much fuel to stay in this position. And the great thing about L2 is that, not only are you orbiting the Sun, but at any time, the Sun and the Earth are in one place, they’re all in one direction. So you can block out all of the light and all the heat from the Sun. So you’re always gonna have a very, very dark place. And you can also make sure that your antenna’s always pointed towards Earth so you can beam all of the data back. Now, there are some trade-offs with that. So you can’t send astronauts out to L2 to fix it if anything went wrong, like you could for Hubble, but it’s very important that you can always keep the telescope very, very dark because one of the things with Hubble orbiting around the Earth every sort of 90 minutes, every once in a while, the Sun’s gonna get in your way. And every once in a while, the Earth is gonna get in your way.

And so, if you were trying to observe something for a very long period of time, it’s just not necessarily efficient if you have to stop every 90 minutes while the Earth transits through. You can be much more efficient with your observatory if you’re at a part of space like L2. Now, because astronauts actually can’t go and fix it if something breaks, we really needed to test this thoroughly. We couldn’t have a case like what happened with Hubble, where the mirror just wasn’t correct. And so, JWST has been really rigorously tested. Much more so than any other space mission. In fact, this image here is showing you the actual telescope body itself, so the main primary and secondary mirrors, everything was inserted into a cryogenic chamber at the Johnson Space Center in Texas, and it was actually tested in these cryogenic conditions to make sure that everything looks perfect. So this is actually the largest cryogenic chamber in the world, originally designed for the moon landing missions, and it simulates the conditions of space. So we could be sure that JWST would work when it was actually in space and it would be able to get the sharp, crisp pictures that we were expecting. Now, I’ve already alluded to this weird little apron around it.

It’s actually about the size of a tennis court. So this is it, sort of separate from the mirror. What is it? It’s actually five layers of material called Kapton and it’s designed as a sun shield. So these very, very thin layers of material are gonna be blocking all of the light and all the heat from the Sun, so that you go from having a very bright and very hot side of the telescope to a very dark and a very cold side. In fact, the hot side of the telescope is going to be about 128 degrees, and the cold side of the telescope is gonna be less than 380 degrees below 0. And that’s significantly colder even than a Wisconsin winter. These five layers progressively make it colder and colder and darker and darker with this material. And so, you can actually get much, much colder temperatures than you could, for example, with just one layer. This is really important, of course, because the colder your telescope is, the better the infrared pictures are going to be, but this system is also completely passive. So there’s no refrigeration, there’s no coolant.

There’s no reason that this system is going to get worse over time, okay? This is a very important consideration when we’re talking about the longevity of a space-based mission. Now, its mirror also looks very different. In fact, its mirror is 18 individual hexagonal segments that are put together. These segments are really interesting and really special. They’re each made out of beryllium. So beryllium is really useful to make telescope mirrors because it’s very lightweight and it also doesn’t change shape when it changes temperature. So you can imagine going from the hot side of the telescope to being cooled down to 380 degrees below 0, there’s a significant amount of temperature change, and most materials would crack or change shape, but beryllium doesn’t. So it’s really, really good at making these mirrors. Now, on the left, what you can see is actually the back plate of one of the mirror segments. It has this sort of honeycomb structure to optimize the strength, but also to lower the weight.

So with anything that goes into space, weight is a really important consideration. The heavier your telescope is, the more difficult it is to launch. So everything was designed to be extremely lightweight. So as soon as these mirrors were actually coated with their shiny surface, the final thing is an extremely thin layer of gold was applied. Essentially, kind of like gold leaf. And the reason for that, why it’s gold as opposed to aluminum like Hubble, is that gold is really good at infrared astronomy. So gold is really good at reflecting infrared light. Much, much better than the typical sort of aluminum that you would see in a normal telescope. So all of this was meant to be optimized for the infrared. Now, this thing is big.

That sun shield’s the size of a tennis court. The whole thing, when it’s fully assembled, is gonna be 26 feet tall, and that’s just simply too big to fit inside any rocket. And so, in particular, the European Space Agency uses Ariane 5 rockets which are, essentially, the largest that we have for this kind of application. So the whole thing actually needed to fold up into about 35 by 15 feet. So here’s some pictures of it when it folds up in its folded configuration. And then, in the end, this is when it was finally being put into essentially the nose cone for the rocket. Now, all of this folding up is one thing, but that also means that this whole thing needs to unfold. And that sounds scary. All of this needs to happen remotely. All of this needs to happen independently.

You can’t, if something gets stuck, go and hit it with a hammer; everything needed to work. Moving parts, redundancy, everything was built exactly for this purpose, tested exquisitely well, and everything worked flawlessly. So I’ll walk you through the deployment sequence a little bit, just to say, generally, what was happening and when it was happening. After the launch, about half an hour after launch, after it left the Earth’s atmosphere, was that initial separation between the telescope and the spacecraft. And that was that last picture that we could see. And that’s the bottom end of the telescope. Just a few minutes later, the first solar panel was deployed. Now, all of the electronics on JWST are solar powered. So this was very important that this step actually worked. And then, over the next few days, was when we started to deploy the sun shield.

So the sun shield itself is contained in these two pallets, these fore and aft pallets that needed to unfold first. So that took a few days. And very importantly, they needed to be protected during launch. These things can’t get dirty and they can’t get ripped. The material is about as thin as a human hair. So it’s extremely delicate. So there were covers that were put on the sun shield after it was folded up extremely carefully. The covers came off and then these two large boom arms, first one and then the other, actually extended outwards from the center of the spacecraft. And those boom arms pulled the layers of material with them. A few days after that was when the tensioning actually happened.

So we actually needed to apply tension to pull the individual layers apart so that all five would become separated. So if they were stuck together, they wouldn’t work as efficiently in terms of cooling the telescope. So this whole process happened very, very slowly and, of course, very successfully. A few days after that, so a total of 11 days after the start of the launch sequence, is when the secondary mirror deployed. Now, most telescopes have at least two mirrors. They have the primary mirror, so that’s the large, gold thing you see in the background. And they also have that secondary mirror, which, in this case, is on those three little boom arms. The secondary mirror actually takes the light from the primary mirror, it focuses it, and puts it inside the telescope where actually you have your detectors. So that’s where you’re actually taking the pictures. So the secondary deployment was really, really crucial because everything else could have worked, but if the secondary mirror didn’t deploy, there wouldn’t be any way to get the light inside the telescope.

Finally, those two little ears, or wings, of the primary mirror were the last things to unfold. This is about two weeks after launch. So you get this fully assembled hexagonal primary mirror. Now, we weren’t done at that point. So it’s very, very important because you have these individual segments to make sure they’re all in exactly the right place. So they’re essentially trying to mimic if you had a monolithic mirror. So there were little actuators on the back of each of the segments. And a lot of time was spent making sure that all of the light coming off of every individual segment was pointed in the right place. Was pointed in the right place on the secondary mirror. And so, you go from having a configuration where things look a little bit off to then, very slowly and very progressively, making sure that everything is in focus and perfectly done.

And this whole thing took about two months. Ever since then, we had commissioning of instruments, we had turning everything on, making sure everything was cold, testing everything, everything is working flawlessly with the mission. What are we going to see with it? So I’ve spent a lot of time talking about what was really the primary motivating theme for the mission, which was understanding the earliest phases of the universe. Understanding what the first galaxies looked like and when they formed. So as I said with Hubble, we’ve pushed back to 4% of the age of the universe. What is beyond that? So we like to be a little poetic and talk about this because, essentially, these were the dark ages. We don’t know very much about what happened. And there has to be a point before then, before the first stars formed, when there really just wasn’t any light. The universe was a dark place. And that all ended at some point.

The first stars started to glow and produce light. And at the end of it, we have a universe like the one around us today, full of galaxies. And how did that happen? What were the first stages actually like? JWST was really, really designed and built to help us answer this question. Going beyond that, when we’re just talking about galaxies, how do galaxies grow? How do they evolve? What did our Milky Way look like when it was younger? We can’t really observe any one galaxy changing on a sort of meaningful time scale, right? It takes millions and millions of years. We can’t see things changing for the most part. So we actually do kind of like population studies. So I’m showing you now these four images. These are galaxies in the local universe. And as you move from left to right, we’re going from smaller to larger in terms of the number of stars, and we’re going from younger to older. But the thing is, if you want to understand how that old galaxy looked when it was young, when it was young, the universe was a very different place.

So you can’t rely on looking at pictures of young galaxies today to understand what old galaxies today used to look like. In fact, it’s almost like if you’re talking about with people. If you wanna understand how people change with time and you don’t have a documentation of any one person, you need to look at pictures that are old. ‘Cause your grandparents, for example, they probably looked very different as babies than you did, right? Everything changes with time. So if you wanna understand the oldest galaxies, you need to understand younger galaxies at earlier times in the universe. And since light travels at a fixed speed, you look at more distant galaxies. And so, you have to put the whole picture together this way, by doing these sorts of population studies at different distances, when these different distances represent different ages, different epochs of the universe. Putting everything together is something that we’ve done a lot with Hubble, but we need the ability with JWST to push back to the earlier times. And importantly, even in more recent times, to go and find the things that are the smallest. To find what galaxies look like, even today, that are just being born, because they’re so small, they have so few stars, they’re actually very, very difficult to observe.

So JWST is really gonna help us, not only with the first chapters, but really sort of completing the storybook of what happens with galaxies and how they change over time. How did our galaxy come to be the way that it is? Now, on very different fields, JWST is also going to be extremely useful. So for example when we’re talking about how stars and how planets are formed. I mentioned that before, and I showed you that initial picture of the Pillars of Creation. And I said that the stars are being born inside those columns of gas. And it’s really frustrating because if you want to see the first stages of stars and planets forming, it’s always sort of enshrouded by gas. Now, luckily, if you’re looking at infrared light, you can actually kind of peer through the clouds. So as I said, Hubble has some infrared capabilities. And as you can see in this image on the right, with the infrared light, you can see straight through. You can see through the gas, and you can actually see, at the sort of tips of these columns, the bright stars that are being born.

So JWST is going to continue this kind of work, get much more sensitive images, also for different parts of the galaxy, different regions so we have a much better idea of how stars form and how planetary systems form around those stars to help really put into context is our solar system interesting or unique? How often does it happen? We need to see these things as they form in order to be able to answer those kinds of questions. And finally, and arguably the most important of these, is how does life start? So infrared light is also very, very good to detect signatures of water and carbon dioxide and methane in the atmospheres of other planets. That’s exactly why it’s very difficult to observe in the infrared from the Earth. So our atmosphere is full of water vapor and carbon dioxide, which absorbs infrared light. But exactly because of this, you would expect to see stars and planets around other stars that might have these elements. You can take a spectrum, for example, and learn more about the characteristics of the atmospheres of these planets. So we’ll be able to learn how unique is a place like Earth? How unique is water, in any of its forms, in planets around other stars? So the sort of major science themes, the major sort of questions that we’re going to answer with JWST, how did the universe form? What was it like at the very earliest times? What were the first galaxies like and the first stars like? And how can we piece together the picture of how the universe came to be the way that it is that we see it today? Is our solar system unique? Do we know, are there other systems with planets that are similar to ours, where you have terrestrial inner planets, gaseous outer planets? How often do you expect to see planets forming in what we call the habitable zone, where liquid water can exist on the surface of a planet? What are the stars that actually host those systems like? Should we expect to have sun-like stars with systems of planets like ours? There’s a lot more that we still have to learn about the formation of stars and planetary systems. And are we alone? Are there other planets that, once we’ve met all of these criteria, that could have life, that could have signatures of life? Could they have water? Could they have carbon dioxide? Could they have methane? It’s a really exciting time for us to be able to understand the earliest parts of the universe and all of the things that are even more nearby. Our place, how unique are we? So it’s going to be a really exciting time with JWST. Everything worked flawlessly.

In fact, everything worked even better than expected. And so, we can believe that since the launch of December 25th, 2021, we’re gonna have at least 10 years’ worth of time to be using JWST to answer many of the questions that we have. And I think, very importantly, based on our experience with Hubble, we’re gonna be able to answer questions that we don’t even know that we have right now. We’ll be making so much progress that we’ll be able to hone and develop new scientific ideas, new questions, and learn so much more about the universe than we could have ever imagined. It really is going to be that exciting of a time. And this only could have happened because this is such a large international partnership. As I said, there were three space agencies involved, numerous aerospace contractors, and scientists, thousands of scientists and engineers from around the world. This is truly an international collaboration, and it was, arguably, the only way that something this transformative could ever happen. We need to bring all of these wonderful, smart people together to do great things. So this image here was the first image that was ever taken with JWST.

You could see there’s a bright star in the center with that characteristic set of diffraction spikes. Everything worked, everything took very clear pictures. And the thing that I’m most excited about that you can see in the background, there are a lot of galaxies in this picture too. So it’s going to be really, really exciting over the next 10 years to use JWST to learn about the universe. So I really thank you for your attention. There’s plenty of really great resources available online. NASA’s websites, there’s webtelescope. org. Here at UW, you can learn about the science that we’re going to do. There’s so much more to learn.

I really hope I’ve sort of stimulated your curiosity about the universe, about JWST in particular, and I really, really hope that you learned something and that you come away from this with a little bit more excitement about the universe, and a little bit more curiosity about who we are, where we come from, and what it all means. So thank you very much.