Seven Earth-sized planets orbit the same ultracool star

摘要

Discoveries of planets around distant stars have become almost routine. But finding seven exoplan-ets in one go is something special. In February, a team of planet seekers announced that a small, cool star some 39 light-years away, TRAPPIST-1, hosts the most Earth-sized exoplanets yet found in one place: seven roughly Earth-sized worlds, at least three of which might host liquid water (SN: 3/18/17, p. 6).