NASA’s New Space Telescope Is Poised to Discover Hidden Facets of the Universe - WIRED

Astronomers have known for decades that an invisible substance permeates the cosmos. Detected only by its gravitational influence on visible objects, dark matter accounts for some 85 percent of all matter, enveloping entire galaxies in great spheroids that branch and interweave to form the scaffolding of the universe.

But the specifications of this grand architecture remain shrouded in mystery. Driven by a ghostly force that scientists call dark energy, the universe is ever-changing, constantly expanding at an accelerating rate.

A new space telescope, launching as soon as August 30 from NASA’s Kennedy Space Center in Florida, will attempt to untangle the nature of these dark intergalactic phenomena. With the resolution of Hubble and a field of view about 100 times as big, the Nancy Grace Roman Space Telescope will provide a new way to look at the universe that could help solve some of the biggest questions in astrophysics.

“An observatory like Roman is intrinsically a discovery machine,” says Julie McEnery, NASA’s senior project scientist for the space telescope. “We're going to find rare things, unusual things, new things, surprising things.”

During its five-year primary mission, Roman will map expansive swaths of space to develop a comprehensive picture of galaxies and dark matter, helping scientists understand how the universe’s largest formations change over time. The telescope, named for the first chief astronomer of NASA, will trace astrophysical structures by measuring subtle distortions of light caused by gravity, allowing scientists to study how dark energy is driving cosmic evolution.

“We’re not measuring the property of something in the universe,” McEnery says of this work. “We’re understanding how the universe we’re in fundamentally works.”

Roman’s sharp, wide view is also expected to capture as many as 200,000 new planets, an extraordinary leap from the roughly 6,300 confirmed exoplanets. The telescope will spot most of these worlds as they block some of the light from their host stars, but its high sensitivity will allow it to detect an additional 1,000 or so by measuring the planets’ gravitational effects on starlight.

Given the space telescope’s powerful resolution and wide area of study, there’s no telling exactly what else it may find.

“The most exciting science from Roman,” McEnery says, “may well be something that we can't even imagine now.”

In many ways, Roman will be a partner to the James Webb Space Telescope. Both primarily observe infrared light, and like Webb, Roman will orbit a point in space nearly a million miles away from Earth called Lagrange Point 2, where the telescopes can effectively block out light from the sun, Earth, and moon.

But where Webb is designed to peer deep into the cosmos, Roman will take a wide view.

“If we consider what the James Webb Space Telescope is doing, it's optimized towards looking at the very distant universe … but just a tiny patch of the sky,” says astrophysicist Rachel Mandelbaum of Carnegie Mellon University. “In contrast, Roman is able to look at a large area of the sky at once.”

That broad view will allow Roman to scour hundreds of millions of stars in search of planets. Similar to previous missions, the space observatory will find most of its targets by looking for planets that transit in front of their host stars. This is a highly effective technique to find large planets with short orbits, but to look for different kinds of worlds, Roman will use another trick called microlensing.

When two stars line up one in front of the other, the light from the background star is warped and magnified by the gravity of the star in the foreground. If that foreground star happens to host a planet, Roman will be able to detect how the planet’s gravity further magnifies the starlight coming from behind.

“This method can detect planets that are farther away from their stars than other methods,” says Matthew Penny, an exoplanet researcher at Louisiana State University. “You don't need the planet to complete an entire orbit before you see it.”

Roman is so sensitive to these microlensing effects that it should be able to detect planets with less mass than Mercury. It will also have the ability to spot free-floating “rogue” planets that have been cast away from their stars or that formed alone in the void.