Astronomers announced today the discovery of an extraordinary planetary system: seven Earth-sized planets that could all have liquid water on their rocky surfaces. The planets circle a tiny, dim, nearby star in tight orbits all less than 2 weeks long.
Although it isn’t possible today to say whether the planets harbor life, astronomers are excited because each planet’s orbit passes in front of—or “transits”—its parent star. What’s more, the system’s proximity to Earth means that answers to questions about whether the system is habitable may come in just a few years’ time with the launch of a powerful new space telescope.
The planets, which circle a star called TRAPPIST-1 just 39 light-years away, are tucked together so tightly that they routinely spangle each others’ skies, sometimes appearing as shimmering crescents and at other times as orbs nearly twice as large as the full moon.