NASA Says Roman Telescope Could Detect Around 100,000 Exoplanets

NASA said Thursday that its Nancy Grace Roman Space Telescope could detect around 100,000 exoplanets, a projected haul that would dwarf the roughly 6,300 worlds confirmed so far and sharply broaden the search for planets beyond the solar system. The agency said Roman’s galactic bulge survey is expected to observe about 100 million stars in the dense central region of the Milky Way.

The figure is a forecast, not a count. NASA said Roman is expected to find about 100,000 planets through transits — the small dips in starlight that occur when a planet crosses in front of its host star — and more than 1,000 additional worlds through gravitational microlensing, which detects planets when a foreground star’s gravity briefly magnifies the light from a more distant star.

The scientific significance is not just the volume. Most exoplanets found so far have come from surveys of stars in the Sun’s broader neighborhood, largely in the Milky Way’s disk. Roman is designed to push that work much farther into the galaxy, especially into the crowded galactic bulge, giving astronomers a way to compare planet populations across very different galactic environments.

“Our galaxy is home to a variety of different environments, but when it comes to hunting for exoplanets, we’ve really only explored one: our own neighborhood,” Elisa Quintana, an astrophysicist at NASA’s Goddard Space Flight Center, said in the agency’s update.

Roman’s exoplanet reach depends on its Wide Field Instrument, which NASA describes as a 300-megapixel camera with 18 detectors. Its images cover a patch of sky larger than the full moon, allowing the telescope to monitor vast star fields at once. During the bulge survey, NASA said, Roman will track about 100 million stars and is expected to record more than 50,000 microlensing events, which can reveal planets as well as other compact objects.

That scale sets Roman apart from earlier planet-hunting missions. NASA said its now-retired Kepler space telescope revolutionized the field by surveying about 100,000 stars. Roman’s bulge survey, by contrast, is expected to observe around 100 million stars, trading a local census for a much broader look across the galaxy.

Transit detections should make up the overwhelming majority of Roman’s projected finds. Those signals are strongest when a telescope can repeatedly measure tiny brightness changes in huge numbers of stars. Microlensing will add a different slice of the exoplanet population, because it does not rely on catching a planet passing in front of its star. Instead, it uses gravity itself as a lens, making it useful in regions and configurations that other methods can miss.

NASA’s headline estimate is grounded in simulation work and should be read that way. A 2023 pixel-level simulation study projected roughly 60,000 to 200,000 transiting planets for Roman’s Galactic Bulge Time-Domain Survey, depending on observing assumptions such as cadence and how the mission handles crowded stellar fields. The agency’s “around 100,000” figure sits within that range.

Roman’s survey could do more than expand the catalog. NASA said the telescope may be able to study the atmospheres of perhaps a few thousand of the transiting planets it discovers, offering a chance to compare not just how many planets exist in different parts of the Milky Way, but some of their physical properties as well.

“Roman will extend the search far enough to encompass other galactic habitats, which could help us learn how planet formation varies across different regions of the Milky Way,” Quintana said.

The mission is now in prelaunch testing. NASA’s timeline says Roman is targeting launch as soon as early September 2026, with a formal commitment of no later than May 2027.