Gliese 581c is an extrasolar planet (or exoplanet)orbiting the red dwarf star Gliese 581. It appears to be in the circumstellar habitable zone (or ecosphere), a notional spherical shell of space surrounding stars where the surface temperatures of any planets present might maintain liquid water. Liquid water is vital because of its role as the solvent needed for biochemical reactions. As such, Gliese 581 c is one of the first truly "Earthlike" planets discovered outside of the Solar System.
Gliese 581c compared to Earth:
- Gliese 581c has a radius 50% larger than the Earth.
- Gliese 581c has 5 times the Earths mass.
- Gliese 581c has a gravitation fieldthat is about 2.2 times stronger than that on Earth.
- Gliese 581c is 14 times closer to its star than the Earth is to our Sun.
- Gliese 581c has an estimated surface temperature between 0 and 40°C, the average surface temperature on Earth is around 15 °C.
- Gliese 581c is one of three planets so far discovered in the Gliese 581 system, as opposed to the 8 planets in our solar system.
The planet was discovered by the team of Stephane Udry of the Geneva Observatory in Switzerland using the HARPS instrument on the European Southern Observatory 3.6 meter telescope in La Silla, Chile, and is the smallest extrasolar planet discovered to date. Udry's team employed the radial velocity, technique, in which the size and mass of a planet are determined based on the small perturbations it induces in its parent star’s orbit via gravity.
Talking to BBC News, Alison Boyle, curator of astronomy at the Science Museum, London, said: "Of all the planets we've found around other stars, this is the one that looks as though it might have the right ingredients for life.
"It's 20 light-years away and so we won't be going there anytime soon, but with new kinds of propulsion technology that could change in the future. And obviously we'll be training some powerful telescopes on it to see what we can see. 'Is there life anywhere else?' is a fundamental question we all ask."