The Nancy Grace Roman Space Telescope is NASA’s next flagship orbital observatory, with the power to reshape what we know about planets throughout the galaxy and help uncover the true nature of dark matter and dark energy. It is a mission on the same scale as the Hubble Space Telescope or the James Webb Space Telescope.

Why is NASA launching the Roman Space Telescope?

Roman is expected to revolutionize our sense of how common different kinds of planets are by discovering thousands of worlds beyond the Solar System. While humanity has confirmed about 6,000 such worlds (known as exoplanets) over the past few decades, Roman could discover many more than that entirely on its own. The mission will also take direct photographs of planets and explore some of their atmospheres, as well as find potentially Earth-like worlds around other stars.  

At the same time, Roman will investigate dark energy, which scientists identified decades ago as a mysterious phenomenon causing the accelerated expansion of the Universe. Dark energy could be an undiscovered particle, a property of spacetime itself, or something else entirely — no one knows for sure. By conducting a massive survey of over 1 billion galaxies, Roman will narrow the search by mapping the structure of the Cosmos through space and time.

This survey will help researchers probe another strange cosmic unknown: dark matter. Like dark energy, dark matter is a name scientists have given to something additional that is needed to fully explain certain aspects of the Universe (in this case, how galaxies move and how the Universe has evolved over time). Many researchers argue dark matter is likely to be a substance that does not interact with light. Together with dark energy, this puzzle hints at undiscovered physics, new kinds of particles, and possibly different predictions for the ultimate fate of the Universe. 

For these reasons and many others, the U.S. astronomical community rated Roman the highest-priority large space mission of the 2010s.

What will the Nancy Grace Roman Space Telescope do?

Roman will repeatedly photograph the sky in huge swathes to look for planets, map galaxies, and discover supernovae, among other things. Based on what scientists predict to be out there, the mission is expected to:

• Find hundreds of rogue planets that orbit no star, including some worlds as small as Mars
• Discover thousands of planets, including smaller, more Earth-like worlds that past surveys have been less likely to spot
• Uncover dozens of planets (at least) orbiting in the habitable zones of their stars
• Take direct photos of exoplanets, possibly including the first image of an exoplanet with rings
• Find up to approximately 1,000 previously unknown moons of Jupiter, 200 moons of Saturn, 100 moons of Uranus, and 5 moons of Neptune
• Detect 80,000 Type Ia supernovae, a specific kind of supernova that is useful for mapping the Universe
• Possibly confirm the first-ever exomoon 
• Survey over 1 billion galaxies
• Study up to nearly 100,000 cosmic voids

Scientists predict Roman will detect somewhere within the range of 60,000-200,000 candidate planets using the transit method, which involves watching stars to see them temporarily dim as orbiting planets pass in front of them and block some of their light from reaching Earth. Only a small fraction of these candidate worlds will be able to be confirmed, though. Roman is also expected to discover thousands of planets using a technique called microlensing.

At the same time, Roman will take direct images of planets using a coronagraph, an instrument that blocks the light from a star to make the worlds around it more visible. The coronagraph onboard Roman is at least 100 times more powerful than any existing facility. It will allow Roman to detect planets that are roughly 1 billion times dimmer than the stars they orbit, testing out the technology for future missions like NASA’s planned Habitable Worlds Observatory. 

When will the mission launch?

Roman is scheduled to launch on Aug. 30, 2026, from NASA’s Kennedy Space Center in Cape Canaveral, Florida. It will lift off aboard a SpaceX Falcon Heavy rocket, then make its way to a region of space called Sun-Earth Lagrange Point 2, about 1.5 million kilometers (930,000 miles) away. There, the gravitational pull from the Sun and Earth balance in a way that will allow the spacecraft to stay in a stable, efficient orbit. The NASA/ESA/CSA James Webb Space Telescope is also located around Lagrange Point 2, though the two observatories are expected to fly very different orbits. 

After roughly 90 days of commissioning, the telescope will begin science operations at the beginning of 2027. Its primary mission is slated to last five years. If all goes well, though, Roman could continue operating for more than twice as long. 

What sort of cool photos should we expect to see?

Think of the images that Hubble introduced to the world — upgraded. At certain optical and infrared wavelengths, Roman will be able to take images just as sharp as Hubble’s but capture 100 times more of the sky in a single shot. This means that, combined with other upgrades, Roman will be able to survey the sky about 100 to 1,500 times faster than Hubble could. JWST, on the other hand, is more sensitive than Roman will be but has a view of the sky about as narrow as Hubble’s. With Roman, we can expect breathtaking, broader views that capture rare objects and events in the Cosmos.

The Hubble Space Telescope, for instance, once stared at a tiny patch of sky for 11 days to produce the mind-boggling Ultra Deep Field image. Roman could take an image that sees just as deeply into the Universe — or even deeper — in the same amount of time, but capture an area about 100-200 times the size.

Roman should also treat us to direct images of planets orbiting other stars, including, perhaps, the first image of a ringed planet orbiting another star.  

Who was Nancy Grace Roman?

Nancy Grace Roman was NASA's first chief of astronomy. She shepherded many of NASA’s earliest space telescopes through development, and in the 1970s, she organized astronomers around a mission called the Large Space Telescope, advocating for its development and eventually becoming the mission’s first program scientist. That telescope went on to become the Hubble Space Telescope. In 2020, NASA decided to rename its new flagship space telescope (then called the Wide Field Infrared Space Telescope, or WFIRST) after her. Roman is the first NASA space telescope to be named after a woman.