NASA is preparing to open a new set of eyes on the universe, designed to see not just individual stars and galaxies but the cosmic landscape. The Nancy Grace Roman Space Telescope will survey enormous areas of sky, repeatedly observing them to study how the universe has evolved and to search for answers to some of astronomy’s biggest questions.

Roman is designed to investigate dark energy and dark matter, map the growth of galaxies and other cosmic structures, and conduct an unprecedented census of planets beyond our solar system. Its strength is scale. Its Wide Field Instrument will see more than 100 times as much sky in a single image as Hubble while surveying the sky more than 1,000 times faster.

That makes Roman a fundamentally different tool from the James Webb and Hubble space telescopes. Hubble and Webb can spend significant amounts of time studying individual objects in extraordinary detail. Roman will provide the broader view, finding enormous populations of objects and identifying unusual targets for closer examination.

“Roman doesn’t do Hubble science faster,” said Julie McEnery, Roman’s senior project scientist. “It addresses entirely new ambitious science questions while Hubble continues to do the great things that Hubble does.”

Measuring a changing universe

One of those questions is why the expansion of the universe is accelerating. Scientists call the unknown cause dark energy, but they do not yet know what it is or whether its properties have changed over cosmic history.

Roman will tackle the problem by surveying billions of galaxies and measuring how cosmic structures have grown and changed. Its observations of galaxies and supernovae will help scientists reconstruct the history of the universe’s expansion and test whether today’s standard model of cosmology holds up.

There are already hints that it may not. Measurements of the expansion of the universe and the growth of cosmic structure have produced tensions with current predictions. If Roman confirms those discrepancies, scientists could have to consider possibilities ranging from changing dark energy to a fundamental revision of how gravity works on the largest scales.

“We’re likely to go beyond standard models and explore entirely new phenomenon for the first time,” McEnery said.

Roman’s repeated observations also will allow it to catch cosmic events that happen quickly, including exploding stars and stars being torn apart by supermassive black holes. Because Roman can watch such a large area at once, it should find rare events that previous telescopes often missed.

A census of other worlds

Roman will also search for planets using two complementary techniques.

The transit method looks for the tiny dip in a star’s brightness when a planet crosses in front of it. Gravitational microlensing takes advantage of the way a planet’s gravity can bend and magnify light from a more distant star.

Microlensing is particularly important because it can find planets farther from their stars than transit surveys typically can, including Earth-sized planets in the outer portions of habitable zones.

“Roman’s going to help us complete the outer edge of the habitable zone and complete that census,” said Shawn Domagal-Goldman, director of NASA’s Astrophysics Division.

The same technique could reveal objects that are difficult to find by other means, including rogue planets drifting through the galaxy and isolated black holes and neutron stars.

Seeing planets directly

Roman’s Coronagraph Instrument will take a much narrower approach. It will stare at individual nearby stars and attempt to block their overwhelming glare so astronomers can see faint planets orbiting them.

Vanessa Bailey, the coronagraph’s principal investigator, compared the challenge to “trying to see a firefly next to a lighthouse.”

It uses masks and deformable mirrors that can make extraordinarily precise adjustments to the telescope’s optics, suppressing scattered starlight. The goal is not to photograph an Earth twin. Instead, the instrument will demonstrate technology that could eventually make that possible.

Scientists hope Roman will directly image Jupiter-like planets and study their reflected light, potentially revealing clues about their atmospheres. They also will examine dusty debris disks around stars for evidence about how planetary systems form.

Augmenting Webb and Hubble

Roman will work alongside the Hubble and Webb Space Telscopes rather than replace them. Its enormous surveys can locate unusual galaxies, planets and transient events, while Hubble and Webb can follow up with detailed observations at visible, ultraviolet or infrared wavelengths.

The mission also is taking a different approach to its enormous volume of data. Rather than requiring researchers to download the entire archive, NASA is building a cloud-based system where scientists can work directly with Roman’s observations. The data will be publicly available without an exclusive period, and the system will allow teams, including students, to analyze the observations together.

The first discoveries could come quickly, with early observations expected to reveal new planets and unusual objects. The larger questions about dark energy, dark matter and cosmic evolution will likely require years of observations.

NASA emphasizes that the most important discovery may be something they did not anticipate.

“I very much hope, and in fact expect, that the most exciting science from Roman will be a surprise,” McEnery said.

⁠NASA+ coverage begins at 6:20 a.m., or join fellow space fans at the ⁠North Carolina Museum of Natural Sciences’ Roman Space Telescope Launch Party,  7 a.m. Sunday in the SECU Daily Planet Theater and will show the NASA livestream on the theater’s 40-foot screen.