Paris, 25 Jan 2006
An international team of astronomers has discovered a planet more similar to Earth than any found to date. This groundbreaking discovery of a new extra solar planet, or exoplanet has been made by scientists searching for Earth-like planets capable of supporting life. The first details of this discovery are made in today's edition of Nature. Altogether 160 exoplanets have been found since the first was discovered in 1995, but all of them have been very different to those found in our solar system. This new planet, which is only about 5-times as massive as the Earth, is the smallest exoplanet ever found orbiting a star. Designated OGLE-2005-BLG-390Lb, the exoplanet is around 25.000 light years away from the Earth, close to the centre of our own galaxy the Milky Way. It has an orbital period of 10 years and is about three times as far from its parent star as the Earth is from our Sun. The new planet was found using the 'microlensing' technique, described by the leader of the RoboNet microlensing planet search, Prof. Keith Horne of the University of St. Andrews in Scotland, as the "fastest way to find small cool planets down to the mass of the Earth...". If we can deploy robotic telescopes at additional sites in the southern hemisphere we can expect to find several more cool planets every year, which could include the first detection of extra-solar Earths" comments Malcolm Fridlund, study scientist for ESA's Darwin mission. "This is a very important discovery" says Malcolm Fridlund, study scientist for ESA's Darwin mission. "It is the first planet which is likely to be 'rocky' i.e. similar to the composition of the Earth, Venus and Mars, as opposed to gas giants of the Jupiter type. Planets of the terrestrial type are of course the 'holy grail' for those who search for life in the Universe." "ESA is also involved in the Corot mission to be launched later this year, which will search for planets occulting their parental stars. A planet like OGLE-2005-BLG-390Lb found closer to its star would be easy for Corot to pick up and this discovery makes it even more probable. For ESA it also implies that "missions like Darwin will be more likely to succeed in its quest to study true Earth-like planets in detail" explains Fridlund. ESA's Darwin is intended to search for Earth-like planet, the most likely places for life to develop. Darwin will survey 1000 of the closest stars, looking for small, rocky planets. Darwin will be a flotilla of four free-flying spacecraft that will search for such Earth-like planets around other stars and analyse their atmospheres for the chemical signature of life.
Corot, due for launch at the end of this year, will be the first mission capable of detecting rocky planets, several times larger than Earth, around nearby stars (planets outside our Solar System are referred to as 'exoplanets'). Corot is led by the French space agency CNES. ESA joined the mission in October 2000 by agreeing to provide the optics for the telescope and to test the payload. As a result of the collaboration, scientists from ESA's Member States will be given access to the satellite's data.