Planet finding has become mainstream,” says MIT astrophysicist Sara Seager. “It’s remarkable how quickly it went from being hard and challenging to ‘Hey, let’s train the next student to find planets.’ ”

In the roughly quarter century since the first exoplanets were discovered, astronomers have found thousands of them. And the field is shifting from tallying celestial bodies to unraveling mysteries: How do planetary systems form? How do planets form? How typical is our solar system? Is there life elsewhere?

In the decade following the first discoveries, scientists studied exoplanets one at a time. Then statistical studies ramped up because of the many planets found by NASA’s Kepler mission, which monitored a 115 square-degree patch of sky from 2009 to 2018. The Transiting Exoplanet Survey Satellite (TESS), launched last year, marries the two approaches. TESS will scan 85% of the sky to identify candidate planets, which astronomers can...

You do not currently have access to this content.