How NASA’s Nancy Grace Roman Space Telescope will open a window into the Milky Way

Look up at the night sky with the naked eye and it may seem like it rarely changes. Yet the universe is in constant flux. Stars drift through space, orbiting the center of the Milky Way as planets orbit them. They rotate, showing spots on their surfaces and sometimes producing violent outbursts that affect planetary atmospheres much like solar storms produce auroras on Earth.

As stars age, they can die dramatically as supernovae, releasing material that will form the next generation of stars and planets.

A new NASA telescope—named after NASA’s first chief of astronomy and first female executive, Nancy Grace Roman—will let us observe these changes to the night sky, almost as if we are watching a cosmic high-definition movie.

This is thanks to three capabilities working together: sharp images, a huge field of view and repeated observations.

Watching the sky change

The Nancy Grace Roman Telescope is often described as the successor to the Hubble Space Telescope. It has a mirror the same size as Hubble’s and also observes visible and infrared light. But it can observe a much larger patch of the sky—up to 200 times larger.

Usually, seeing a bigger patch of sky means sacrificing spatial resolution. Both the Kepler and the Transiting Exoplanet Survey Satellite planet-hunting telescopes have watched enormous numbers of stars, but their lower spatial resolution means nearby stars can blend together.

On the other hand, the James Webb Space Telescope can see more sharply, but its much smaller field of view makes it impractical for monitoring millions of objects at once. The Roman telescope combines high resolution with a wide field of view.

The final key to Roman’s power is time: by repeatedly observing the same patches of sky, Roman will reveal changes that a single image could never capture.

Those changes unfold on timescales ranging from hours to years, revealing different physical processes. By tracking how the light of objects changes over time, Roman can distinguish patterns and use them to uncover what is happening throughout the universe.

Two of Roman’s core surveys are designed to watch different parts of the sky for different kinds of change. The High-Latitude Time-Domain Survey will capture distant phenomena such as supernovae, while the Galactic Bulge Time-Domain Survey will monitor the packed center of the Milky Way.

A window into the Milky Way

In the galactic bulge, thousands of stars (along with gas and dust) obscure our view of the center of the galaxy. To our eyes, these same stars appear as an almost solid, smeared white “Milky Way.”

Roman, however, can see the individual stars and use them as a backdrop for research.

One of the primary focuses of the Galactic Bulge Time-Domain Survey is finding objects through microlensing. In this process, gravity from a passing object warps and magnifies light from a distant star behind it, giving us a better view of that star.

These passing foreground objects can include stars, Mars–sized planets and even black holes hundreds of times the mass of the sun.

Roman will also find planets using the transit method: Planets dim starlight as they pass in front of their stars, revealing their presence. The sheer number of stars in the galactic bulge means astronomers predict they will find around 100,000 transiting planets.

What changing starlight reveals

Staring at stars can also reveal how they rotate and change over time. This is particularly interesting for the smallest and coolest stars.

Along with magnetic spots, clouds are also expected on the surface of stars cooler than roughly 2,500°C (4,500°F). As the stars rotate, these features come in and out of view, allowing astronomers to measure their rotation periods.

Comparing rotation across many targets can reveal patterns in how these stars change over long timescales. Yet these stars are quite faint and red, making it incredibly difficult to study large numbers of them with current surveys.

The Transiting Exoplanet Survey Satellite, which has observed almost the entire sky over the past eight years, has revealed rotation periods for hundreds of these tiny stars. But it observes in visible light, where these stars appear relatively faint, and its low spatial resolution makes crowded fields challenging.

Roman’s wide-field, high-resolution and near-infrared observations can significantly increase this sample, allowing astronomers to study rotation and activity across a much larger population of the smallest stars. A larger and more diverse sample could reveal how these stars’ environments vary, helping us understand worlds found around them.

From supernovae in distant galaxies to the smallest stars in our own, Roman will capture a cosmos that is constantly changing. Look closely, and the seemingly static sky is anything but.

Who’s behind this story?

Swati Mestri

Swati Mestri holds a bachelor’s degree in Electronics Engineering and has worked as a content editor since 2019. She has experience editing research documents across technology, health care, and materials science, and has a particular interest in technology and space.

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Andrew Zinin

Master’s in physics with research experience. Long-time science news enthusiast. Plays key role in Science X’s editorial success.

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This article is republished from The Conversation under a Creative Commons license. Read the original article.