Thirty years ago, the only planets we knew of were in our own solar system. Since then, we’ve discovered thousands orbiting alien suns, but most of these exoplanets are so far away that it’s difficult to study them in detail. Though we’ve learned a lot, one major question remains: How common are planets in star systems with more than one star, like the binary suns that shone on Luke Skywalker’s home world in Star Wars?
Multi-star systems themselves are commonplace; roughly half of sun-sized stars have at least one stellar dance partner circling in orbit with them. But does having a stellar neighbor affect the likelihood of any planets forming around a star? Or would the motions of stars in a multi-star system instead fling a planet away, exiling it to the lonely depths of space?
Astronomers like Courtney Dressing of the University of California, Berkeley, are finally starting to tackle these questions, with help from an orbiting observatory called the Transiting Exoplanet Survey Satellite (TESS). Once it completes its primary two-year mission (likely by July 2020), TESS should reveal thousands of new exoplanets — NASA estimates about 20,000 — orbiting the nearest and brightest stars. Dressing and other astronomers will then follow up with telescopes on Earth, checking whether planet-hosting stars have stellar partners, or they dance alone. The efforts will help us learn where and how planets form, and, ultimately, the kinds of planets on which life can arise.
