More science news.. [*ahem* – Ed] Whilst some people have leapt to a somewhat dubious conclusion, it is a remarkable achievement by the astronomers using the ESO 3.6m telescope in Chile to identify the effects of the smallest exo-planetary mass yet detected, only 5 times the mass of the Earth and approximately 50% larger in diameter. It’s part of a three exo-planet system orbiting a star, Gliese 581, in the constellation of Libra just 20.5 light years away. The reason for the excitement is that, despite being close enough to the star to complete an orbit in only 13 days, the exo-planet lies in what is known as the habitable zone – with an average surface temperature of between 0-40 degrees Celsius water would exist as a liquid.. and where there’s liquid water.. there’s [possibly] life.And they’ve thoughtfully provided a YouTube video report
Extra detail from the ESO press release
: Using the radial velocity method, astronomers can only obtain a minimum mass (as it is multiplied by the sine of the inclination of the orbital plane to the line of sight, which is unknown). From a statistical point of view, this is however often close to the real mass of the system. Two other systems have a mass close to this. The icy planet around OGLE-2005-BLG-390L, discovered by microlensing with a network of telescopes including one at La Silla (ESO 03/06), has a (real) mass of 5.5 Earth masses. It, however, orbits much farther from its small host star than the present one and is hence much colder. The other is one of the planets surrounding the star Gliese 876. It has a minimum mass of 5.89 Earth masses (and a probable real mass of 7.53 Earth masses) and completes an orbit in less than 2 days, making it too hot for liquid water to be present.
: Gl 581, or Gliese 581, is the 581th entry in the Gliese Catalogue, which lists all known stars within 25 parsecs (81.5 light years) of the Sun. It was originally compiled by Gliese and published in 1969, and later updated by Gliese and Jahreiss in 1991.
: This fundamental observational method is based on the detection of variations in the velocity of the central star, due to the changing direction of the gravitational pull from an (unseen) exoplanet as it orbits the star. The evaluation of the measured velocity variations allows deducing the planet’s orbit, in particular the period and the distance from the star, as well as a minimum mass.