Garching, Germany - Astronomers said Monday they have detected a distant planetary system with three planets not much bigger than our Earth, one of the most promising discoveries ever in the hunt for life in outer space. Unlike most of the 300 so-called exo-planets discovered in the past 13 years, the trio are small enough to perhaps have rocky surfaces. Most of the 300 have been huge gas planets such Jupiter and Saturn, which cannot sustain life as we know it.
The head office at Garching near Munich of the European Southern Observatory (ESO) said the trio were orbiting star HD 40307 in our own Milky Way galaxy, 42 light years away from Earth.
The discovery was announced at the three-day Extra Solar Super-Earths conference which began Monday in Nantes, France.
The star is visible from the Southern Hemisphere between the constellations Dorado and Pictor. HD 40307 is fairly similar to the Sun. A super-earth is defined as a planet with up to 15 times the mass of our planet, ESO said.
The trio had between 4.2 and 9.4 times the mass of Earth, calculations of a wobble in HD 40307 prove.
However their periods of orbit around the star are quite fast at 4.3, 9.6 and 20.4 days. Exo-planets with rapid orbits are easier to find than any with a 365-day orbit like the Earth.
The trio were detected with the HARPS spectrograph, a device attached to the 3.6-metre ESO telescope at La Silla in Chile.
Internet: Extra Solar Super-Earths Konferenz: www.sciences.univ-nantes.fr/geol/SuperEarths2008
