Tomorrow morning, if all goes to plan, NASA’s Nancy Grace Roman Space Telescope, its latest and greatest orbital observatory, will lift off from its launchpad and add a little rocket-booster light to the Florida sunshine. A lot is riding on this mission. If the Roman is successful, it could give humanity a new way to see the planets around other stars and a fresh understanding of the largest-scale objects that we know to exist. But if it fails, NASA’s science program, which is already fending off ruinous budget cuts, will need to seriously rethink its future. The Artemis mission to the moon was a big win for human spaceflight, and now the science side of the house badly needs one.
NASA’s engineers have spent more than a decade readying the Roman for this moment. Before the telescope arrived in Florida, it spent more than a year in NASA’s largest clean room at the Goddard Space Flight Center in Greenbelt, Maryland. To get near it, you had to be mummified alive. When I visited in December, NASA staffers led me to a sterile, fluorescent-lit locker room. They tossed me a white jumpsuit and two sets of booties with tight-fitting straps. They told me to put on a beard net and hair net, and triple-wrapped the gap between my jumpsuit sleeves and gloves with blue tape.
The astronomers didn’t want my skin exposed in the clean room. Dry flakes of it could drift off and settle onto the telescope’s ultrasmooth primary mirror. “You’re going to be the dirtiest thing in here,” one of them told me, as we walked through a little chamber where more than 30 nozzles blasted us with air. I jotted down this remark on special mint-green paper that sheds fewer particulates than a regular notebook, and then stepped into a cavernous eight-story white space soundtracked by the hum of six school-bus-size fans. At its center, the Roman stood more than 40 feet high, and it was surrounded by more than a dozen people, all in identical jumpsuits. Half were standing in clusters, talking, while the other half were up on motorized lifts, fussing with the telescope, applying duct tape and making final adjustments. More than a thousand people have worked on this project, and those who are lucky enough to get close to the hardware seem to derive a physical pleasure from the experience.
[Read: Inside Donald Trump’s attack on NASA’s science missions]
The Roman has a pretty shady backstory for a scientific instrument. Its primary mirror was part of a surprise gift bestowed on NASA by the National Reconnaissance Office. The NRO is one of America’s most secretive government agencies, and it apparently had a Hubble-class spare just lying around. A cash-strapped agency can’t afford to be too choosy about provenance: NASA took this mirror that was supposed to point down at the ground, for surveillance, and will instead point it out at the stars.
The NRO’s spare mirror has also solved a bit of internal politics for NASA’s science program. The Roman is built to monitor the universe at the very largest scales, to map the cosmic superstructure of galaxy clusters that stretches out from us in every direction, to see how it has expanded over time. These observations might lead scientists to a more refined sense for gravity, and may even help them discover new physics. But the idea for a mission like this was originally conceived of around the early 2000s, shortly after the discovery of dark energy, and a survey of the large-scale universe seemed like the obvious next thing to do. When NASA was finally ready to build the telescope, in the early 2010s, the action in astronomy had shifted closer to home. Scientists were in the midst of discovering thousands of new planets around nearby stars, and they wanted to find more. Although the Roman’s original mission plan did allow for some planet-hunting, the new mirror would allow them to do it in a whole new way.
[Read: The Nobel Prize winner who thinks we have the universe all wrong]
Finding a little world with its own atmosphere in the glare of a nearby star is tricky work. Even the very largest planets will be a billion times fainter than the suns they orbit. When I spoke with Dominic Benford, Roman’s program scientist at NASA Headquarters, he likened the challenge to spotting a firefly buzzing around a powerful searchlight from thousands of miles away. To make this possible, astronomers have lodged an exquisite new kind of coronagraph into the Roman’s metallic guts. Coronagraphs originally helped astronomers see the plasma flares emanating from our sun, by blocking out the far more brilliant light from the solar disk. In a sense, the device creates a brief artificial eclipse inside the telescope. The Roman’s coronagraph is designed to do something similar for more distant stars so that astronomers can see the planets that surround them.
When the telescope is trained on a star in our Milky Way, it will catch a lot of light, and then run it through the coronagraph’s system of barriers and mirrors. Two of the mirrors that it uses may be even more beautiful in their design than the ultrasmooth, eight-foot primary. Each is smaller than the average makeup compact, and has more than 1,600 actuators that can individually deform tiny portions of the glass in tiny increments, less than the diameter of a helium atom. Astronomers will employ hundreds of these warping movements, spread across the mirrors, to deflect a specific star’s glare, creating an image of the star within a ring of nearly pure darkness. Deformable mirrors like these have previously been used on the ground to help telescopes see through the warble and blur of Earth’s atmosphere. But no one has ever sent one of this complexity to space.
The Roman team believes that up there, where the viewing conditions are more pristine, the Roman will be able to deliver the first direct images of distant planets in visible light. Until now, most of the extrasolar planets that scientists have observed have been detected indirectly. In some cases, a planet’s existence is inferred from the gravitational force that it exerts on its host star, causing the star to wobble. Or astronomers might see a host star dim, repeatedly and predictably, as an orbiting planet passes in front of it. We have been able to get direct snapshots of only a few young planets that were still roiling hot and glowing brightly, and mainly in infrared. The Roman telescope’s coronagraph should be able to see worlds that aren’t glowing at all. Like Earth, they will be illuminated solely by the soft visible light of their host stars.
[Read: When a telescope is a national-security risk]
I asked Vanessa Bailey, the coronagraph’s instrument technologist, if there were any particular stars that she was excited to inspect. Because the coronagraph isn’t part of the telescope’s main mission, just three of the first 18 months will be set aside for its observations. Bailey said that the astronomers will use that time to look at previously detected planets that are only tens of light-years away. She mentioned the Epsilon Eridani system, where a Jupiter-size world is known to orbit an orange dwarf star. With the coronagraph, they’ll stare at it for many hours, letting photons from the planet slowly pile up. “It’s just going to be a little fuzzy smudge, just barely there,” Bailey said. “But we might be able to tell if it’s cloudy or clear, and we might be able to say whether it’s more like Jupiter or Neptune.”
All of this could go wrong. Bailey told me that the coronagraph has never been tested outside the lab, and in space, it may not work. If for some reason the mirrors are misaligned, or the instrument malfunctions, any planets would be lost in the astral glare. NASA’s long-running quest to find another living world in the universe would be set back, perhaps by a decade or more. But if the coronagraph does fulfill its mission, it will serve as a proof of concept for NASA’s next really big telescope, the Habitable Worlds Observatory, which the agency has been developing for more than a decade.
Roman’s coronagraph will be able to find only large planets—Saturn-size or ideally bigger—that circle their stars in chilly, distant orbits. NASA scientists want to place a much more precise one on the HWO. That mission will fixate on more than 100 nearby stars that share the sun’s rough age and brightness. Its coronagraph will cast a much tighter ring of near darkness around them, to see if any planets show up in the closer, warmer orbits that might be more hospitable to life—and it will even look for signs of life in the planets’ atmospheres. But the HWO won’t lift off until the late 2030s at the earliest. For now, the Roman has to prove out. It has to survive the violence of launch and fly a million miles from Earth so that its mirrors can catch the light of a nearby star and then surround it in darkness so deep that a faint alien world appears.
The post A New Way of Seeing Alien Worlds appeared first on The Atlantic.
