What the Webb Space Telescope Will Show Us Next
By David W. Brown
Since the European Space Agency launched NASA’s James Webb Space Telescope from French Guiana, on Christmas Day, 2021, the telescope has hovered in space about a million miles from Earth. During its voyage, the J.W.S.T. unfolded like a piece of origami, releasing an array of solar panels, a powerful antenna, a honeycomb of golden mirrors, and a sunshield that looks like a set of silver sails. Scientists then spent more than three months aligning its mirrors with nanometre precision. About a year after the telescope released its first images, Jane Rigby, the top NASA scientist working on the project, told me that it has “performed not only better than requirements but better than we could have possibly dreamed.” Recently, the Webb helped to show that galaxies in the first billion years of the universe were more active than previously thought, forming lots of stars in big bursts. “There were predictions, but this was terra incognita, past the cliff of what Hubble could do, and expectations were all over the map,” Rigby told me. “Where we had ignorance, we now have beautiful data.” Recently, in celebration of the telescope’s first year of science operations, the Webb team published an anniversary image of stars being born in the Rho Ophiuchi cloud complex, the stellar nursery closest to Earth.
The first telescopes were made of two pieces of rounded glass in a tube. Galileo Galilei discovered Jupiter’s moons, and thus showed that the Earth was not the center of the universe, with a telescope that could magnify twenty times. Six decades later, Isaac Newton completed the first successful reflecting telescope, using a concave mirror that concentrated light much more efficiently. Over the centuries, telescopes have grown and improved enough to spot increasingly faint and faraway celestial objects. The Webb represents a culmination of this progression. It is a hundred times as powerful as the Hubble Space Telescope and sees infrared light that is invisible to the human eye. (Light falls on a spectrum from longer wavelengths to shorter wavelengths: infrared, red, orange, yellow, green, blue, indigo, violet, ultraviolet.) It was designed, in part, to gather light that has been travelling to Earth since shortly after the Big Bang. When astronomers point its mirror toward the edges of space, it sees the universe as it was thirteen billion years ago—close to the literal dawn of time.
Rigby works at NASA Goddard Space Flight Center, in Greenbelt, Maryland, and has been part of the James Webb Space Telescope team since 2010, as an astrophysicist and, since June, as the J.W.S.T.’s senior project scientist. We spoke via video chat during her lunch break; while I asked her questions, she jabbed a fork into a Tupperware that she had brought from home, and then chewed thoughtfully as she considered her answers. She is an animated storyteller, often punctuating her points with hand gestures and minor adjustments to her black horn-rimmed glasses. I asked her about the telescope’s peculiar design, the ways that astronomy shapes our everyday lives, and the gaps in human knowledge which the Webb has already started to fill in. Our conversation has been edited and condensed.
When the Hubble Space Telescope launched, we soon learned its images were blurry. Engineers had to build the equivalent of eyeglasses for it. Were there any such problems with J.W.S.T. early on, given its very complicated deployment?
Because of the way it worked, when Hubble went up in space, the optics had to be perfect. For J.W.S.T., we launched mirrors that were able to fix themselves. There are eighteen primary mirror segments—those beautiful gold hexagons—and the idea is that you design them to be correctable in space. You just move them until they’re in the right places. When J.W.S.T. first deployed, through this long, iterative process of looking at bright stars, we got all of those mirrors to work together like a chorus—where, at the beginning, everybody’s in their own key, their own song, their own genre, doing their own thing. And, at the end, they’re coördinated, singing in a tight, multipart harmony.
The real problem with J.W.S.T. was that we needed a telescope bigger than rockets are. The rocket we launched on is a little more than five metres across. But just the telescope part of J.W.S.T. is 6.6 metres across (and then there’s this whole sunshield underneath it that’s the size of a tennis court). One way to overcome the size limit, which is a fundamental challenge for space telescopes, is to have them fold up. Six of the primary mirror segments were tucked back behind the rest of the mirrors for launch. Then they unfolded on hinges. So that led to a design where we didn’t need to align them perfectly on the ground.
If size is but one challenge for space telescopes, what you would say is the greatest one?
Oh, my gosh. I think, right now, the greatest challenge is just time. The telescope is about one hundred times more powerful than anything we’ve had before. In the same observing time, it can see things that are a hundred times fainter than we could see with Hubble or with the Spitzer Space Telescope. So it is this powerful beast, and, in the first year of science operations, we have about five hundred different observing programs—in total, thousands of people from all over the world—who are using this telescope.
In a given day, we will observe a quasar, which is an accreting black hole that is as far away as we can see, and then, a couple of hours later, we’ll go observe an asteroid in our own solar system. Then we might go observe a nearby galaxy. We have a schedule, and we are doing observations that were selected competitively by the scientific community as the most compelling. And we are doing observation after observation, and then getting those data out to the world. The ingredient for discovery is just time.
What are the main questions J.W.S.T. must answer for this mission to have been considered a success?
Well, it’s worth taking a moment to go back a bit. Hubble launched in 1990, and there were three key questions that it set out to answer. One was: How old is the universe? Which is really a measurement about how fast the universe is expanding. We now know that that wasn’t the most exciting question to ask. In the course of measuring that expansion of the universe, astronomers came to understand that the universe’s expansion is accelerating. That was the unexpected discovery.
The second one was: What are quasars, and what is their relationship to galaxies? Well, from work with many telescopes, including Hubble, we now know that quasars are supermassive black holes of a million to a billion solar masses in the hearts of galaxies that are fuelling—that is, they are feeding on gas, and even destroying stars—and, in doing so, are shining as bright or brighter than their parent galaxies. We know that every galaxy has such a black hole in its heart but that most of them are asleep. A small fraction of them, however, are turned on and are fuelling. We don’t really understand how the black holes and their parent galaxies evolve together. We have evidence that one’s controlling the other, but we don’t know how.
Third, Hubble was also built to study the gas between galaxies. And we now understand that galaxies are constantly being fed by this web of gas that links galaxies together—like, this structure spanning the void with a beautiful kind of filamentary geometry. And we know that how galaxies are connected to that network determines how they’re able to fuel and grow. It’s fun to think back over thirty years and realize how little we understood thirty years ago, and how far we’ve come.
What about J.W.S.T.?
For J.W.S.T., the questions that we knew we were going to ask were: What did the first billion years look like? How did galaxies get started? From the data we have so far, we’re going to do a great job on that question. We are finding galaxies further back than we knew were possible. We’re seeing back in time to about three hundred million years after the Big Bang. The elevator pitch we used when J.W.S.T. was sold was that we’ll see the baby pictures of the universe. And we will definitely do that.
J.W.S.T. was also built to study the atmospheres of planets orbiting other stars. That’s the other really high-profile science case. And we’re doing that, but we haven’t gotten far enough yet during our first year of science observations.
What gaps in science do the J.W.S.T.’s unique capabilities fill?
J.W.S.T. works in the infrared. It was designed to see the light from the universe that is totally invisible to Hubble, which sees primarily in the optical and ultraviolet. About the “bluest” light that J.W.S.T. can see is the shade of red wine, and then it goes redder from there.
Because of the Big Bang, space is expanding—not just stuff in space but the fabric of space itself. And the light that we see from distant objects has actually been stretched by the expansion of the universe as well. That causes light from those distant objects to get stretched to longer wavelengths. It gets shifted to the red, to lower energies.
It’s just really cool that we can see almost to the end of the universe, right? We can do that because that light only travels so fast: the speed of light. We are studying galaxies whose light has been travelling for more than thirteen billion years. The universe is only about 13.8 billion years old! Those are the baby pictures of literally everything, and, in particular, of the baby galaxies that would have turned into mature galaxies like our Milky Way.
Why else does J.W.S.T. need to see in the infrared?
Much of the universe is filled with what we call dust but is really more like smoke. And that smoke hides what we are trying to see. In particular, the places where new stars are born are really dusty places. You can’t see through them with an optical telescope for the same reason that your eyes can’t see through them. A telescope like Hubble can’t, either. But infrared light just goes right through the dust. It gives us a view of a part of the universe that was previously hidden. We think half of the stars in the universe are hidden to us, but using J.W.S.T. and the infrared, they should pop into view.
Perhaps this is a limitation of my childhood education, but knowing now that light is stretched, I am curious how else light travelling for thirteen billion years across the entire universe will be altered before it gets here. Is what we are seeing what it actually looked like?
So you are asking, basically, did anything happen to the messengers along the way?
In general, no, but, in some ways, yes. That’s actually a really lovely question. The light gets stretched, but light can also get absorbed. There’s a neat technique we can do in astronomy where we go find a distant flashlight, and then we study the light that’s missing because it has been absorbed by gas along the way. Photons can also get scattered. But, other than those two things, it really doesn’t change the fundamental picture. We really are getting a snapshot of what things looked like back in the day. And I certainly didn’t learn any of that in school!
How long have we known all this? I once read that, in terms of structure, the human mind had everything it needed to build the Hubble Space Telescope about one hundred thousand years ago: we just didn’t have the technical ability to do it. But, if that weren’t a limiter, how long ago would we have known the right questions in order to build J.W.S.T.?
I love this question, because you’re right: modern humans have been around for a couple hundred thousand years. I know that because I took my kid to the Hall of Human Origins at the Smithsonian. Ancient humans would have known the Milky Way much more intimately than we do, because today we have light pollution. But astronomy was a part of their daily lives, both in their storytelling and, once we invented agriculture, for when to plant the crops.
Certainly, I assume people would have been asking the big questions around campfires for as long as we’ve had language and been modern humans with big brains. How did it all get started? Are we different from the other animals? What came before this? Are there other planets? Are there other places like this? The really cool thing about living now is that we can get some real answers to those questions.The technology that built J.W.S.T. is the same technology you would need to build a telescope to go survey Earth-like planets around nearby stars and see if there’s life there. That’s amazing, right? We’ve always been wondering, since there have been humans, are we alone? But we’re within a generation of having the technology to just go find out. Not even a generation. One or two decades.
The beautiful Milky Way up there isn’t the only one like that. There are thousands. So how did it come to be? We’ve only known what stars are made of since the fantastic 1925 thesis of Cecilia Payne-Gaposchkin—probably the best astronomy thesis ever written. That was her thesis! Can you imagine that? Like, we all sit down and say, I’ll have to do something useful for my thesis. And hers was, O.K., here’s what stars are made of. Because nobody knew! She used this brand-new science of quantum mechanics, along with data that were coming out about the fingerprints of stars, and she figured out what stars are made of. That still blows my mind. Stars are made of hydrogen and helium, with a bunch of trace elements, and she figured it out. Can you imagine a state of knowledge that’s so wide open?
Don’t you think we still live in that world in some ways?
Maybe we do. Because we don’t know what most of the mass and energy in the universe is. We know what about four per cent of the universe is made of—the stuff like us. Baryonic matter. But we don’t know what dark matter is, even though there’s way more of it out there. It’s baffling and annoying. And we don’t know what dark energy is. It’s this weird repulsive force that is making the universe expand ever faster and faster. That’s ludicrous—what is that? We didn’t predict that, but it’s there. There are theses to be written in which someone solves dark matter, or in which they figure out what dark energy is.
What big, outstanding question in astronomy would you most like to see answered in your lifetime?
Oh, gosh. You know, this is going to make me feel a bit like a traitor to my field, because I study how galaxies evolve, how galaxies form stars, and what galaxies are made of and what they’re like. That’s what I do. And there are enough interesting and important questions about that to last a couple of lifetimes. But, as much as I love that science, I think the most important thing that astronomy could do is figure out whether we’re alone in the universe. Figure out whether there are other planets that are not only habitable but inhabited. What’s our place in the universe? I don’t know of a more profound question than that. I would hope—but this might be the idealist in me—that regardless of the answer, it would help us as a species to take better care of the one planet that we know can sustain life. It could be the case that this is a very rare oasis in a lonely universe.
Are these telescopes better at giving us new questions or definitive answers?
Sometimes our paradigms get overthrown, and we push back the frontiers of our own ignorance. We now know, for example, how to make gold. When I was in graduate school, we didn’t know where in the stars gold gets made. We now know—thanks to the Laser Interferometer Gravitational-Wave Observatory—that gold comes from a certain kind of exploding star.
When I was in high school, we did not know how many other planets there are orbiting other stars and how rare they might be. NASA’s TESS told us the answer. But then we asked a more interesting question: What are they like? So we have to go and do all the chemistry that J.W.S.T. is doing to understand what those planets are like. And then we could say, Well, could any of them support life? And that’s still a more complicated question. So maybe it’s that we answer the basic questions, and we move on to more nuanced, but, in some ways, more profound, questions.
Something that you touched on is that, for centuries, astronomy was invaluable across a swath of everyday life—everything from agriculture to navigating the ocean to calculating holy days of obligation. Everyone felt its effects. How is astronomy still part of the realm of the practical, or does astronomy today pretty much exist for astronomers?
Astronomy still underpins our lives, and probably more than it used to. It’s just invisible. G.P.S. uses general relativity as developed and tested on astronomical objects. Without relativity, G.P.S. would stop working in a couple of minutes. We still rely on calendars to tell us when to do stuff. We measure when we need to add these tiny little leap seconds to keep our calendars accurate. Every time you use your phone to take a picture, you’re using a C.M.O.S. digital camera that was in large part developed for astronomy. So there are lots of practical aspects, but that’s not why we do astronomy.
Fundamentally, astronomy is about knowing how we got here. And everyone has wondered that. How did I get here? What’s the point? What’s the big picture? What’s bigger than me? And what will be here when I’m gone?
Is that what draws us to images from J.W.S.T.?
I think there are two reasons astronomy is so compelling, and has an outsized place in the public consciousness, even though there really aren’t very many astronomers. We make the front pages of newspapers in part because what we’re doing is visually stunning. Because the universe is a beautiful and marvellous place. I still find it surprising that we see the universe as beautiful, because our brains didn’t evolve for that. They evolved not to get eaten by sabre-toothed tigers. To communicate and coöperate, survive and work together. But we see the universe as beautiful. Part of what astronomers are doing is providing that sense of connection and wonder. Astronomy shows us what’s out there.
The story that the data tell is that all of the elements in our bodies, except for the hydrogen in water molecules, were made in stars. All the oxygen, all the carbon, all the nitrogen, all the iron: all of that was made in stars, and then spat out through multiple generations of stellar explosions, supernovae, and then that debris coalescing into new stars. So we’re part of the story, literally. Carl Sagan said, profoundly, that we are made of star stuff, and it is really true, except for the hydrogen that’s left over from the Big Bang. Even the iron that’s carrying the energy around your body was made in a stellar explosion involving what we think is a Type 1A supernova—an old star. The carbs that you’re eating, the oxygen you’re breathing—all of that was made in massive stars that blew up really fast. And so, literally, this is our origin story. ♦When the Hubble Space Telescope launched, we soon learned its images were blurry. Engineers had to build the equivalent of eyeglasses for it. Were there any such problems with J.W.S.T. early on, given its very complicated deployment?If size is but one challenge for space telescopes, what you would say is the greatest one?What are the main questions J.W.S.T. must answer for this mission to have been considered a success?What about J.W.S.T.?What gaps in science do the J.W.S.T.’s unique capabilities fill?Why else does J.W.S.T. need to see in the infrared?Perhaps this is a limitation of my childhood education, but knowing now that light is stretched, I am curious how else light travelling for thirteen billion years across the entire universe will be altered before it gets here. Is what we are seeing what it actually looked like?Yes.How long have we known all this? I once read that, in terms of structure, the human mind had everything it needed to build the Hubble Space Telescope about one hundred thousand years ago: we just didn’t have the technical ability to do it. But, if that weren’t a limiter, how long ago would we have known the right questions in order to build J.W.S.T.?Don’t you think we still live in that world in some ways?What big, outstanding question in astronomy would you most like to see answered in your lifetime?Are these telescopes better at giving us new questions or definitive answers?Something that you touched on is that, for centuries, astronomy was invaluable across a swath of everyday life—everything from agriculture to navigating the ocean to calculating holy days of obligation. Everyone felt its effects. How is astronomy still part of the realm of the practical, or does astronomy today pretty much exist for astronomers?Is that what draws us to images from J.W.S.T.?