Planet discovered in star's Goldilocks zone

There has been a third planet discovered orbiting the star Gliese 581 in the constellation Libra. The planet is approximately 5 times as massive as the earth and is closer to its star than Mercury is to the Sun.

There have been over 200 exoplanets discovered so far, but most of them have been hot gas giants which are unlikely to support life, at least as we know it. However, Gliese 581 is a red dwarf type star, which means it is a lot cooler than the Sun, and this new planet is orbiting in the stars Goldilocks zone, not too hot - not too cold - but just right for water to exist in its liquid phase.

So if the planet is of the rocky-type, has water, and if its atmosphere is of the right composition, not too thick and not too thin, then it may be habitable. Those are pretty big ifs and planets like these are not thought to be rare but what is significant is that this planet is only 20.5 light years away from the Earth. This distance is large but not insurmountable.

Photosynthesis on other worlds

Research at the California Institute of Technology's Virtual Planet Laboratory suggests that if plant life exists on other planets the dominant color of photosynthesis could be yellow, orange, or even red instead of the usual green. The particular color would depend on the type of star(s) the planet which has plant life orbits and the planet's atmosphere, which filters the light. For example there is a bacteria on earth that uses infra-red light in photosynthesis because it lives in murky water where little to no visible light reaches.

This is good news for science fiction, where plant life has often been unimaginative, though H.G. Wells' depiction of red plant life in The War of the Worlds in 1898 is an important exception. Other sci-fi ecosystems of note include Harry Harrison's psychic plants in Deathworld and Alan Dean Foster's silicon based life in Sentenced to Prism.

Press release.