Meet Gliese 667C, the little star with the big family. Gliese 667C resides near the “stinger” stars in the tail of Scorpius the Scorpion. You can even see it in binoculars on a clear night low in the southern sky. But it’s what you can’t see that makes this star so cool. It’s swarmed by at least six orbiting planets, three of them in the star’s habitable zone where liquid water might puddle on their surfaces.
Three of the six, Gliese 667 Cb, Gliese 667 Cc and Gliese 667 Cd, were found in the past year with Gliese 667Cc orbiting in the habitable zone. This week a team of astronomers using powerful telescopes in Chile and Hawaii announced the discovery of three more planets – Gliese 667 Cd, Ce, Cf – and possibly a fourth. All seven orbit closer to their host star than Mercury does to the sun. Heck, there are so many planets, they completely fill up all the orbital slots in the star’s habitable zone.
Three of them are super-Earths, planets more massive than our own but not quite as big as Uranus or Neptune. Because they circle a much cooler and less massive red dwarf star, they’re not lava-hot hells like so many other extra-solar planets but more temperate worlds where water could be stable. The Gliese system has the greatest number of super-Earths ever found in a star’s habitable zone to date.
Gliese 667 lies just 22 light years from Earth and though it appears single in binoculars, it’s really a triple system. All the planets orbit the dimmest of the three dwarfs, Gliese C, which itself orbits in tandem with a tight pair of orange dwarf stars, Gliese A and B. A resident on any one of the new-found planets would look off toward the pair and see a bright double star shining day or night and providing about as much light as the full moon.
Water as always is key. Given their location, at least three of Gliese 667’s planets have the potential to support life.