The James Webb Space Telescope team prepares for launch
Here’s what the largest—and most expensive—infrared space telescope will set its sights on.
In March 2020, testing teams deployed Webb’s 21 feet 4-inch (6.5 meter) primary mirror into the same configuration it will have when in space. Image Credit: NASA/Chris Gunn
In 1946, 12 years before NASA was created, a Yale University astrophysicist published a paper about the advantages of conducting astronomy research from space. A large space telescope would help, the astrophysicist, named Lyman Spitzer, argued. (Little did he know, an infrared space telescope launched in 2003 would be named after him.)
Forty-four years later, on April 24, 1990, the space shuttle Discovery launched from Florida’s Kennedy Space Center. It carried five astronauts and the Hubble Space Telescope.
Named in honor of astronomer Edwin Hubble, who had shown that there are other galaxies in the universe continually moving farther away from the Milky Way, the telescope was tasked with capturing images from space that are sharper than pictures captured by terrestrial telescopes.
In its 30-plus years, Hubble has orbited Earth for 4 billion miles and has been at the center of 1.5 million remarkable observations. It’s captured images of overlapping galaxies, massive stars, and our planetary neighbors. This fall, Hubble even helped astronomers watch a star go supernova in real time.
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But Hubble, which primarily detects visible light, has its limits. Even after decades of observations, scientists are still trying to “understand some of the big questions,” says Space Telescope Science Institute Deputy Head of Instruments Division Louis Strolger. Questions like, How do the galaxies that Hubble has shown us form and “how do they evolve? And how do they turn into the things that we see today?”
To peer further back in time to the universe’s beginnings and answer questions about the Big Bang and the early evolution of the cosmos, astronomers need an even larger, infrared spyglass. They’re now preparing for the launch of Hubble’s successor, the James Webb Space Telescope (JWST). “With the Hubble Space Telescope, we've been able to scratch the surface of what we know.” says Space Telescope Science Institute Assistant Astronomer Néstor Espinoza. “JWST is really going to expand our knowledge.”
A collaboration between NASA, the European Space Agency, and the Canadian Space Agency, JWST is currently housed at a launch facility in French Guiana on the northeast coast of South America. “Wrapped like a butterfly in a chrysalis of technology, ambition, metal and wires,” Dennis Overbye writes for the New York Times, the JWST “is the biggest, most powerful and, at $10 billion, most expensive telescope ever to be launched into space.” Its complexity means that a lot could go wrong on its launch day, which, after multiple delays related to a loose clamp, broken data cable, and bad weather, is now scheduled for December 25.
Twenty-nine days after its launch, the world’s most advanced telescope will unfurl in its entirety—assuming it skirts past nearly 350 points of failure. Image Credit: NASA's Goddard Space Flight Center Conceptual Image Lab
“It’s taken far longer than we expected to get it all working,” says JWST Telescope Scientist Matt Mountain, hinting at the telescope’s 25-year preparation. “But this is the hardest, most complex telescope humanity has ever built.”
Indeed, scientists initially planned to build a 13-foot-wide telescope (for comparison, Hubble’s mirror is just shy of eight feet wide). But in 1996, Overbye reports, NASA made a bold move: Worrying that the telescope would still be too small to spot the universe’s first stars, the agency settled on building one with a 21-foot-wide mirror, capable of peering at objects up to 100 times fainter than what Hubble can currently detect. Too big to fit onto a rocket for launch, the JWST would have to have origami-inspired folding mirrors that would open up in orbit—a first for a space telescope. “As with all firsts, you get nervous,” Espinoza says, explaining the JWST is an engineering marvel like nothing before. Its mirrors are coated in gold and made of the steel-gray metal beryllium, which, being extremely light, stable, and stiff, “has superior properties at cold temperatures,” says JWST Optical Telescope Element Manager Lee Feinberg.
If all goes as planned, on Christmas the JWST will embark on a million-mile journey to a spot about four times farther away than the Moon. On its way, before assuming a stable orbit around the Sun, the JWST’s mirrors and other parts will open in what NASA calls a nominal deployment sequence. Within two hours of launch, solar arrays and antennas will emerge. And after 29 days, the world’s most advanced telescope will unfurl in its entirety—assuming it skirts past nearly 350 points of failure.
“Our careers, our futures are depending on this telescope,” says NASA Goddard Astrophysicist Amber Straughn. Adds JWST Instrument Systems Engineer Begoña Vila: “We'll all breathe a sigh of relief when everything works as it should.”
After a 6-month cooldown and calibration process, the JWST will turn its gaze to the universe’s early days, a time in history that scientists have never been able to observe with telescopes before. As the current theory goes, about 13.8 billion years ago in a process we call the Big Bang, the universe expanded into being. In a fraction of a fraction of a second, energy transformed into matter. As inflation slowed, it gave way to more matter and radiation, and all that we know of today. But scientists have never seen the Big Bang, of course. “There’s still these holes” in our story of the early universe, Straughn says. “We don't know how galaxies got started.”
This is where the JWST’s great size and use of infrared comes into play. As the universe constantly expands, the light from stars and galaxies shifts over time from our perspective here on Earth. By the time the light from the Big Bang’s earliest creations reaches Earth, it’s stretched from visible blue light to heat radiation that’s invisible to the naked eye and optical telescopes, but whose infrared waves can be detected by a colossal infrared telescope like the JWST. Being so distant in our universe’s past, these infrared waves are incredibly faint. To pick them up, the JWST needs to operate at around -390 degrees F so its own heat doesn’t create background “noise” and interrupt its detections. A sunshield about the length of a tennis court will help keep the telescope cool.
Besides observing some of the earliest galaxies in our universe, the JWST will peer through the dense dust clouds where stars and planets form, helping scientists better understand the evolution of these celestial bodies. “You look at a newborn and you get a feeling for what that person will be when they are grown up. [It’s] the same thing for stars,” says ESA Associate Director Antonella Nota. From observing and measuring them from the beginning, she says, “you can infer how they will be and what they will become.” These observations could also provide clues as to how our own solar system came to be, Espinoza says.
The JWST will also help researchers study the atmospheres of exoplanets, using its infrared instruments to peer at water vapor, methane, carbon dioxide, and other chemical compounds, says JWST Deputy Project Scientist for Exoplanet Science Knicole Colón. But not even the JWST can take pictures of the surfaces of exoplanets, she explains. Rather, scientists will use data collected by the telescope to parse out the chemical composition of atmospheres. From there, they can make more educated guesses as to which exoplanets have the potential to host life.
As with previous telescopes, the JWST team’s goal is to better understand the universe and our place in it. Telescope Scientist Matt Mountain is equal parts nervous and excited for the telescope to launch and commence its observations. Though the JWST team has “tested everything again and again and again,” Mountain says, “I'll be relieved all the instruments are working, all the mechanisms are working. Each one of those steps, I will be relieved, and finally, when we see those first images, we will actually think, OK, it works. Thank goodness.”
NOVA Producer Terri Randall and Digital Producer Ana Aceves contributed to the reporting of this article.
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