NASA is about to turn a new kind of eye on the most crowded part of our galaxy. The Roman Space Telescope, set to launch no earlier than October 2026, will scan the Milky Way's central bulge for planets that other telescopes cannot find. It will use a technique called microlensing, which relies on gravity itself to act like a magnifying glass.
A trick of gravity that reveals hidden worlds
Microlensing happens when one star passes in front of another from Earth's viewpoint. The gravity of the foreground star bends and amplifies the light of the background star. If the foreground star has planets, those planets create their own tiny blips in the brightened light. Roman will watch for those blips.
This method is different from the way NASA's Kepler and TESS telescopes find planets. Those telescopes look for dips in starlight when a planet crosses in front of its star. Microlensing can find planets that are far from their star, or planets that orbit dim stars. It can even find rogue planets that drift through space without a star at all.
Why the galactic core is the best place to look
The Roman telescope will stare at the center of the Milky Way for long stretches. That region is packed with stars, which means more microlensing events happen there. The telescope will monitor hundreds of millions of stars over the course of its mission.
Scientists expect Roman to find thousands of exoplanets, including some that are as small as Mars. It will also find planets in the outer reaches of their solar systems, far from the warmth of their star. These are worlds that other planet hunting methods miss.
What this means for understanding our place in the galaxy
The Roman Space Telescope is named after Nancy Grace Roman, NASA's first chief of astronomy. The mission is managed by NASA's Goddard Space Flight Center in Greenbelt, Maryland. Scientists from around the world will analyze the data.
Local communities near the mission's operations centers have followed the telescope's development for years. The telescope is currently being built and tested. Its launch will mark a new chapter in the search for planets beyond our solar system.
Roman will not just find new planets. It will find whole new populations of planets. It will reveal the kinds of worlds that exist in the most crowded part of our galaxy, a place we have never been able to explore before.
