This week's Sunday Long Read comes to us from Rivka Galchen at the New Yorker, detailing the most powerful space telescope NASA has ever produced, the James Webb, expected to launch in a September mission. Once the space telescope goes online, scientists will have their clearest view yet through a time-travel machine as light from stars that took billions of years to reach us will be on display like never before.
Next month, the James Webb Space Telescope is scheduled to take a slow boat from Los Angeles, spend a few days traversing the Panama Canal, and arrive at a spaceport in Kourou, French Guiana. The telescope will have been twenty-five years and ten billion dollars in the making. Thousands of scientists and engineers from fourteen countries will have worked on it. It could have flown, sure, but it’s a tight squeeze—plus the telescope weighs seven tons, and Kourou’s airfield is connected to its spaceport by seven bridges not built to endure such a load. The telescope will be put into Ariane 5, a European rocket named for a mythical princess who helped a man she loved defeat the Minotaur and escape a maze. Ariane 5 will carry the telescope some ten thousand kilometres in thirty minutes. The J.W.S.T. will then continue on its own, for twenty-nine days, toward a lonely, lovely orbit in space, about 1.5 million kilometres from Earth, where we will never visit it, though it will stay in constant communication with us. From Earth, it will appear ten thousand times fainter than the faintest star.
On its way, the telescope will slowly unfurl five silvery winglike layered sheets of Kapton foil, about as large as a tennis court. These sheets, each thinner than notebook paper, will function as a gigantic parasol, protecting the body of the telescope from the light and the heat of the sun, moon, and Earth. In this way, the J.W.S.T. will be kept nearly as dark and as cold as outer space, to insure that distant signals aren’t washed out. Then eighteen hexagons of gold-coated beryllium mirror will open out, like an enormous, night-blooming flower. The mirrors will form a reflecting surface as tall and as wide as a house, and they will capture light that has been travelling for more than thirteen billion years.
This is the hope, at least.
“Oh, gee, I worry all the time,” said Marcia Rieke, an infrared astronomer based in Tucson, who has devoted much of the past two decades to the J.W.S.T. “Even the rocket, which is the most reliable rocket out there, it still has some tiny chance of exploding at launch.” Rieke, who has astrology-blue eyes and a no-nonsense ponytail, is the scientific lead for the near-infrared camera, known as the nirCam, which is one of four main research instruments on the telescope. She is an expert on the formation of galaxies, and the nirCam will allow us to see light from billions of years ago, when the earliest galaxies and stars were formed. I spoke with Rieke over Zoom, where she had as a background a lunar eclipse she photographed in Sabino Canyon, which is near her home but looks like it’s on Mars. “I’ve spent decades in this field, and there’s still so much I don’t know,” she said.
In 2017, Rieke and her team went to the Johnson Space Center, in Houston, where tests would be performed on the nirCam and other Webb instruments. They wanted to expose the telescope to the extremely cold conditions of outer space. Hurricane Harvey hit while they were there. “While I was at the airport waiting to fly out to Houston, I was watching the forecast and fortunately was able to change my car rental to an S.U.V.,” Rieke said. “So I was able to ferry the members of the team between their hotels and the Space Center. They brought in really nice catering for us. I’m not sure how they managed that.” Imagine sealing one’s gold-plated work of decades in a giant pressure cooker and then pouring liquid nitrogen on top of it—that resembles the exposure test. The telescope was in Chamber A, the gigantic vacuum chamber at the Space Center where the command module for Apollo was tested. Remarkably, Rieke’s team accomplished its mission. Rieke has seen the J.W.S.T. survive not only Hurricane Harvey but also numerous threats of cancellation, along with delays that have serially shifted the launch from an original date of 2010 to late 2021. I asked Rieke what she was most looking forward to seeing. “I’m looking forward to seeing that it works,” she said. “I’ll start sleeping better about thirty days after it’s been launched. Launch isn’t even the riskiest step in deploying the nirCam.” Once the telescope is up and running, Rieke will return to studying events that happened in our universe billions of years before Earth was formed.
It’s easy to forget that light takes time to travel. But when we see the moon we are seeing it as it was 1.3 seconds earlier; Jupiter we see as it was forty minutes ago; the Andromeda galaxy—the nearest major galaxy to ours, and the most distant object we can see without a telescope—2.5 million years ago. “My students are often frustrated to think that they can’t see the things in space as they are today,” David Helfand, an astronomer at Columbia University, said. “I tell them it’s this great advantage. It means that the universe is laid out like a book. You can turn to any page you want. If you want to see ten billion years into the past, you look out at ten billion light-years away.”
Helfand, a former president of the American Astronomical Society, looks like Socrates. He attributes much of his success in life to a background in theatre, and he spends a lot of his time teaching science to nonscientists—the only prerequisite for his perennial class Earth, Moon, and Planets is “a working knowledge of high-school algebra.” He taught me about the J.W.S.T.
Most of the light spectrum is not visible to the human eye. When we look up at the night sky, it’s as if we were listening to Rachmaninoff’s Second Piano Concerto with ears able to hear only the occasional middle C and maybe a tinny D. We have no biological receptors for radio waves, or microwaves, or ultraviolet radiation, or infrared radiation. If an object is moving away from us—and most everything in the universe is, because the universe is continuously expanding—the wavelength of its light is, in effect, stretched out, eventually rendering it infrared. Helfand said, “The atmosphere blocks out a lot of energy—that’s why we can live on Earth. But it’s not good for astronomy. And our atmosphere is particularly ugly for infrared.” On Earth, there are a number of telescopes larger than the J.W.S.T., but they can’t see the range of infrared light with the level of resolution and sensitivity that the new telescope will achieve.
“It will have many capacities, but the two big ones are ‘Very Far Away’ and ‘Very Close,’ ” Helfand said. The Very Far Away component will look back about 13.5 billion years, to when the universe was some quarter of a billion years old. “If you compare the universe’s life to that of a human, that’s like seeing the universe at, well, we’d have to calculate it, but it’s seeing the universe as a baby,” he said. After the big bang, the universe was a nearly uniform soup of matter and radiation. But by the mysterious epoch that the telescope will examine—sometimes called the Dark Ages—gravity had managed to amplify tiny irregularities in that soup, causing a kind of clumping. “So what we are on is the quest for the very first stars.” When did they turn on? What are they like? Did stars form before galaxies? How did black holes with masses millions of times greater than that of the sun form so quickly?
“The Very Close capacity is in some ways the most exciting,” Helfand told me. “It’s about looking at planets that are not too different from Earth.” The J.W.S.T. will study exoplanets, or planets outside our solar system. Exoplanetology is a young field. The first exoplanet (outside science fiction) was discovered only twenty-five years ago. By 2005, about two hundred exoplanets had been found. Today, more than forty-four hundred are known, and it seems likely that such planets are ubiquitous. Though they don’t emit light, Helfand explained that “when these planets pass in front of a star they leave a sort of fingerprint,” and that fingerprint can be read for clues. The J.W.S.T. will be able to describe the atmospheres of these planets, possibly detecting free oxygen or other gases—potential signs of life.
Exciting stuff here, if humanity survives on this rock long enough to be able to reach these exoplanets. We'll see, quite literally.
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