NASA’s Kepler observatory has spotted 20 planets that orbit cool, small stars — the largest such haul so far. These long-lived stars, known as K and M dwarfs, are ubiquitous in the Milky Way and could turn out to host numerous habitable planets.
After the Kepler spacecraft experienced a mechanical failure in 2013 that made it impossible for it to keep observing its original targets, astronomers gave it a new mission, called K2. It now uses pressure from sunlight to help stabilize the craft. The latest observations with K2 revealed 87 planet candidates, on top of 667 previously announced candidates, almost all with sizes between those of Mars and Neptune.
Although the original Kepler mission examined many Sun-like stars, the majority of stars in our Galaxy are smaller, fainter, cooler stars, known as red dwarfs. Such stars make up nearly half the targets of the K2 mission. “There are more than 250 of them within 30 light-years — all over the place — which is why some other astronomers here might call them the vermin of the sky,” says Courtney Dressing, an astrophysicist at the California Institute of Technology in Pasadena who presented the research at a joint meeting of the American Astronomical Society's Division for Planetary Sciences and the European Planetary Science Congress in Pasadena on 19 October.
“Since these stars are the most common ones in the Galaxy, they help us learn how common life might be,” says Victoria Meadows, an astronomer at the University of Washington in Seattle.