Gliese 581c is an extrasolar planet (or exoplanet) orbiting the red dwarf star Gliese 581 at 20 light-years from Earth. It appears to be in the circumstellar habitable zone (or ecosphere, or "Goldilocks Zone"), a notional spherical shell of space surrounding stars where the surface temperatures of any planets present might maintain liquid water. Liquid water is considered vital for extraterrestrial life because of its role as the solvent needed for biochemical reactions. As such, Gliese 581c 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 Earth's mass.
- Gliese 581c has a gravitation field about 2.2 times stronger than that of 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 (32-104°F), with similar temperatures to several earthly climes. Not much snow, but habitable.
- 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.
 See also
- New 'super-Earth' found in space BBC News
- New Planet Could Harbor Water and Life Science.com
- ↑ Yes, 8. Pluto doesn't count anymore, remember?