30 September 2010

Gliese 581 ... «Goldilocks» planet?

Washington Post reports on a recent announcement by Paul Butler of UC Santa Cruz of the "discovery" (in their data from 11 years of observing) of a «Goldilocks» planet in the Gliese 581 red dwarf system that's similar enough to Earth in both mass and amount of stellar radiation received to be potentially habitable... the first such planetary discovery since the first exoplanets were discovered in 1995.

Of course, it's far from identical to Earth. Gliese 581 is a pretty tiny star, giving off only about 1% of the energy of the Sun. This planet is almost certainly tidally locked, like the Moon vis-a-vis the Earth, so it will have peculiar climatic conditions, at minimum. News reports fail to mention also the possiblity of frequent (and probably fatal to nearby planetary life) stellar flares, which are very common in small red dwarf stars.

Still, it's encouraging that a planet with the right mass and distance to primary to have liquid water and other factors necessary for life has finally been found.

Incidentally, Wikipedia quotes an age of 7-11 billion years, significantly older than the solar system. (Time for evolution to have worked even if conditions weren't quite as optimal as here?) On the other hand, the proportion of metals in the stellar atmosphere is rather low, which is thought to hamper the development of life, and see Simon Conway Morris on the rather intractable problems of photosynthesis when the peak radiation from the primary is in the infrared, which is what you have here.

Gliese 581 is 20.3 l.y. distant, in Libra, and is classed as M3V, a bit larger than the median red dwarf type. The Wiki article says it's "thought to be too massive" to be a flare star, so the stellar flare caveat above may not apply.

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