Yesterday two scientists announced the discovery of the first Earth-like planet lying in the habitable zone of its star. Co-discoverers, who will publish in the Astrophysical Journal, are R. Paul Butler of the Carnegie Institute and Steven Vogt of UC Santa Cruz.
It's not exactly Earth -- more like a swollen Mercury, in that the planet is three times the mass of Earth, only 14 million miles away from its star, and does not rotate. The star, Gliese 581, is a dwarf, so even at such close distance any potential water will not have been boiled off the surface. The planet, which goes by the unromantic name of Gliese 581g, orbits the dwarf star every 37 days.
And it's only 20 light years away! That is, as Vogt pointed out in a video, close enough to send a probe with today's technology, even though we might not get any information back for a few hundred years.
The star system appears, from Earth, to be in the constellation Libra. I wish the weather were clear here in Seattle (it's not) -- tonight I'd like to be able to go up to the roof, gaze at Libra, and wonder: Who's there?