The world’s largest space telescope just got an unexpected new role: asteroid hunter

Main belt asteroids in stable orbits aren’t a threat. But this study shows that you can use the JWST, while it’s doing other work, to opportunistically find small-but-hazardously-sized asteroids. Then, if needed, the JWST can team up with other observatories to track these asteroids and determine if any might head our way. (Read more: These five asteroids post the greatest risk to Earth.)

Defenders of the Earth

For the most part, the JWST is busy studying the far-flung cosmos. “Asteroids don’t get a lot of time,” says Sabina Raducan, a planetary scientist at the University of Bern in Switzerland who was not involved with the new study. “But it’s really nice to see what kind of science you can do just by observing something else.”

Finding asteroids with the JWST is a free benefit, and that it can sometimes spy extremely small space rocks that may elude other telescopes is a welcome discovery. But a more devoted observer is on the horizon. NASA plans to launch another space telescope called the Near-Earth Object Surveyor later this decade. It’ll be equipped with infrared detectors and serve as a dedicated asteroid hunter. 

De Wit is keen to stress that the JWST isn’t going to dethrone the NEO Surveyor before it’s even launched. The JWST will also not sideline any of the ground-based observatories that are already pretty effective at spying asteroids. This includes the almost-complete Vera Rubin Observatory in Chile, a next-generation, visible-light telescope set to find millions of new asteroids within the first year of operations. 

“There is no way JWST is going to infringe on their mission,” de Witt says. But his team’s research suggests it will aid planetary defenders. If the JWST captures the same asteroid over several images, you can start to work out what sort of orbit it’s on—and, with the help of other observatories, work out if it’s a main belt asteroid on its way to becoming a near-Earth asteroid.