Nancy Grace Roman Space Telescope Set for Launch to Explore Dark Energy and Exoplanets

The universe is a strange place — filled with exploding stars, ancient galaxies, and unseen worlds. Now, astronomers are about to get a brand new tool to explore it.

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The $4.3-billion Nancy Grace Roman Space Telescope is scheduled for launch Aug. 30. Named for NASA's first chief astronomer, the observatory is expected to reveal new information about the expansion of the universe and discover multitudes of planets orbiting distant stars.

Roman, as it is known to its friends, has an unusual history. About 15 years ago NASA was making plans to build a space telescope that could, among other things, search for exploding stars known as Type 1A supernovas. These supernovas were used as a kind of cosmological measuring stick to uncover a mysterious force called dark energy that was causing the universe to expand — a discovery that earned the Nobel Prize in 2011.

Cosmologist Daniel Scolnic at Duke University says finding more of them would be key to better understanding that expansion.

As NASA was developing plans for this new telescope, a call came in from the government office in charge of surveillance satellites.

"The National Reconnaissance Office reached out to NASA," Scolnic says, "saying, 'We have this amazing satellite sitting in a hangar that we're not using. And what what do you guys think about instead of pointing downwards, we point upwards, and you guys use it?'"

NASA said yes. It took some substantial modifications, but now that old satellite is set to become NASA's next major space observatory.

Scolnic says that the new observatory could fundamentally change the scientific model that astronomers use to understand our universe.

"In the last few years, there have been measurements saying that model might be wrong — and that's something that Roman will absolutely nail, whether the model's right or wrong," he says.

Another goal of the telescope is to spend a month surveying all the stars in the Milky Way galaxy. Julie McEnery is Roman's project scientist. She says even though Roman has broadly the same sensitivity and sharpness of vision as the currently orbiting Hubble Space Telescope, its design lets it do things much faster.

"That one month of observations to survey our Milky Way galaxy would take about a century with Hubble," says McEnery.

Instead of focusing on a single object, Roman is designed to make catalogs of large swaths of the sky, and McEnery says these catalogs will be available to everyone, not just academics.

"You can be a teacher in a high school in Kentucky and your students have the opportunity to see Roman data at the same time as a professor in Princeton," she says.

One professor eager to get his hands on Roman data is Scott Gauti at The Ohio State University. Along with colleagues, Gauti developed a technique for detecting planets around distant stars. It's called gravitational microlensing, and it measures the way those planets bend the starlight that passes them by.

Albert Einstein described the idea in 1936 but thought it would be impractical. New technology has proven him wrong — and Gauti expects Roman will find tons of planets that way.

"We're looking for planets that are just completely undetectable by any other method," Gauti says. That includes planets at the center of our galaxy, "that are very analogous to our own solar system planets like Jupiter, Saturn, Uranus, and Neptune."

In addition to new planets, Roman should also reveal new galaxies, helping astronomers to get a better idea of the large-scale structure of the universe.

But predicting what will be Roman's greatest accomplishments over the course of its five-year-mission is a tricky business.