NASA is about to try a high-stakes disappearing act in space.

When the Nancy Grace Roman Space Telescope launches, as early as the end of next month, it will carry the first space-bound “active” coronagraph, an instrument designed to erase most of a star’s light during photography. That could let astronomers take the first pictures of planets orbiting other stars that are similar to those in our solar system.

“I hope it’s remembered for it being that critical stepping stone for … finding Earth 2.0,” says Brandon Creager, the instrument’s lead mechanical engineer at NASA’s Jet Propulsion Laboratory, or JPL.

Named after NASA’s first chief of astronomy, the telescope will also carry a roughly 300-megapixel wide-field camera. NASA says that camera will capture images about 100 times larger than the Hubble Space Telescope’s widest exposures at a similar resolution.

Those capabilities are expected to help astronomers study dark matter and dark energy, and detect around 100,000 new exoplanets by tracking how they distort the starlight of more distant stars. Javier Viaña, a research scientist at Harvard with two projects selected for Roman’s first year of observing, compares that jump to moving from “interviewing a handful of people” to “conducting a global census.”

A second camera uses the coronagraph to block out a star’s light while observing one stellar system at a time. The instrument is expected to let astronomers see smaller, dimmer and more close-in exoplanets.

“It’s giving us the ability to see planets that we haven’t been able to physically see before,” Creager says.

Coronagraphs already fly in space on Hubble and the James Webb Space Telescope, but those systems are stationary. Roman’s version does something new. Before each observation, it will measure leftover starlight and try to suppress it using a method known as active wavefront control.

The system relies on two deformable mirrors. Each has a 48-by-48 grid of actuators, described as tiny pistons, beneath a thin sheet of glass. A small amount of voltage makes the actuators contract and pull parts of the mirror slightly backward.

Each patch can deform by up to 0.5 micrometres, and in increments as small as approximately 10 picometres. “That’s about a tenth the diameter of a hydrogen atom,” says Ilya Poberezhskiy, the instrument’s project systems engineer at JPL.

Poberezhskiy says the mirrors create an “active wavefront,” with each part positioned to cancel incoming waves of unwanted light. That produces a “doughnut-shaped region around the star where we suppress starlight and where we’re hoping to see exoplanets,” he says.

Compared with current space-based coronagraphs, the system is expected to improve sensitivity to exoplanets against the glare of their host stars by a factor of up to 1,000.

Roman also uses masks, patterned plates placed in the light path to block photons. Some include “silicon grass,” microscopic spikes that absorb photons in certain configurations so they do not bounce around the telescope and reach a detector. “Once the light gets into there, it never gets out,” Poberezhskiy says.

The setup could expand the small list of exoplanets photographed directly. Most of the planets imaged so far are very large, young planets that are several times the mass of Jupiter, still hot from their formation, and orbiting far from their stars.

Roman could instead directly image a Jupiter analogue, a planet similar to Jupiter in mass orbiting a sunlike star a few times farther out than Earth is from our sun. Rather than inferring such planets from the gravitational wobble they cause in a star, Roman will collect starlight reflected from the planet itself.

“We’re not looking at the star. We’re not looking at the effect of the planet on the star,” says Meredith MacGregor, a professor of astronomy at Johns Hopkins who has also secured an observing program. “We are actually looking at the planet, and that is super powerful.”

MacGregor says the data load could be immense. “I’m honestly a little terrified about how we’re all going to deal with it, because I think it’s just so much data,” she says. “I think people will legitimately still be working on Roman data for decades.”

Roman will not produce a sharply resolved image of an alien Jupiter. At best, the planet will likely appear as a few pixels. But MacGregor says the coronagraph can still gather information about the wavelengths of light coming from the planet, which can reveal details about atmospheric chemistry.

“You’re taking something that’s a point of light and turning it into an actual world,” she says, “because if you know that about its atmosphere, now you know something about the surface of the planet and the possibility of life being on that planet, right? So that’s a big step.”

In its first observations, scientists and engineers will test if they can keep a star centred on the coronagraph’s masks, shape the mirrors, “dig” the dark doughnut, as Poberezhskiy puts it, and hold that setup as the spacecraft moves through space and changes temperature.

The results are expected to inform NASA’s proposed Habitable Worlds Observatory, a future mission intended to separate the light of an Earthlike planet from that of a sunlike star more than 10 billion times brighter.

Creager, who has worked on the instrument since 2018, says: “Not too many people get to say, ‘I built something and it’s taking a picture of a planet that’s at a star that’s 50 light-years away or 100 light-years away.’”

Read more from MIT Technology Review.