Europeans discover first habitable planet beyond Earth

Okay, strictly speaking it’s a maybe-habitable planet. But still!

Yesterday the European Southern Observatory announced the discovery of an Earthlike planet orbiting the star Gliese 581. “Earthlike”, to astronomers, is a pretty broad definition; it means a planet that is not so tiny it will lose all its atmosphere to space, nor either so large that its surface will be crushed under hundreds of atmospheres of pressure; and not so cold as to be a frozen iceball, nor either boiling hot. Basically, it’s a planet that can support liquid water.

This is a broad definition, but up until now astronomers have found over 200 planets around other stars without finding a single one that fit. Most were too big — it’s much easier to detect giant planets than little ones, of course — and the ones that weren’t, were either too hot or too cold.

But the new planet — which goes by the euphonious name of Gliese 581c — is a “Goldilocks” world, just right. It orbits Gliese 581c in the “habitable zone”, receiving just about as much sunlight as earth.

Of course, there are some complications. Continue reading