Earth-like planet discovered?

Stephen Withers
Wednesday, 25 April 2007 08:29

Science - Space

Astronomers have discovered a exoplanet possibly capable of maintaining liquid water, and therefore life as we know it.

Unlike previously identified exoplanets, this one is just the right distance from its star to give mean temperatures between 0 and 40 Celsius. Although the star - Gilese 581 - is a red dwarf, the planet orbits close enough to be habitable.

The planet has a very short 'year' of just 13 Earth days. Despite being around 50 percent larger than Earth, it is 14 times closer to Gilese 581 than we are to the Sun. If you superimposed the two solar systems, the newly discovered planet would fall well within Mercury's orbit.

Another difference is that the planet could be rocky, like the inner planets in our solar system. Another possibility is that it is mainly comprised of ice, with a watery surface that formed as it moved closer to its star. Most of the 200-plus exoplanets discovered so far have been gas giants, possibly because astronomers find them by observing the way some stars wobble very slightly as planets rotate around them. Only 13 known exoplanets

Tantalisingly, Gilese 581 is one of our 100 closest stellar neighbours. At the speed of light, a round trip would 'only' take 41 years. The Search for Extraterrestrial Intelligence (SETI) plans to pay renewed attention to the system, even though a previous (if brief) scan failed to detect anything.

One dampener on the excitement surrounding the discovery is the possibility  that the planet, like Mercury, could have one side permanently facing the Sun. In such circumstances, a mean temperature is meaningless, as one side is scorchingly hot while the other is frigid.