5 exoplanets bagged
2010-08-24 16:59
Paris - European astronomers on Tuesday said they had found a distant star orbited by at least five planets in the biggest discovery of so-called exoplanets since the first was logged 15 years ago.
The star is similar to our Sun and its planetary line-up has an intriguing parallel with own Solar System, although no clue has so far been found to suggest it could be a home from home, they said.
The star they studied, HD 10180, is located 127 light years away in the southern constellation of Hydrus, the male water snake, the European Southern Observatory (ESO) said in a press release.
The planets were detected over six years using the world's most powerful spectrograph, an instrument to capture and analyse light signatures, at ESO's telescope at La Silla, Chile.
The method consists of observing a star and seeing how the light that reaches Earth "wobbles" as a result of the gravitational pull of a passing planet. The tiny fluctuation in light can then be used as a telltale to calculate the mass of the transiting planet.
Evidence
The five detected planets are big, being the size of Neptune, although they orbit at a far closer range than our own gas giant, with a "year" ranging from between six and 600 days. The astronomers also found tantalising evidence that two other candidate planets are out there.
One would be a very large planet, the size of our Saturn, orbiting in 2 200 days.
The other would be 1.4 times the mass of Earth, making it the smallest exoplanet yet to be discovered. It orbits HD 10180 at a scorching close range, taking a mere 1.18 Earth days to zip around the star.
If confirmed, that would bring the distant star system to seven planets, compared with eight in our own Solar System.
A total of 402 stars with planets have been logged since the first was detected in 1995, according to Nasa's Jet Propulsion Laboratory (JPL). The tally of exoplanets stands at 472.
None, though, is even remotely similar to Earth, which is rocky and inhabits the famous "Goldilocks zone" where the temperature is just right to enable water, the stuff of life, to exist in liquid form.
New insights
ESO astronomer Christophe Lovis said knowledge was progressing fast.
"We are now entering a new era in exoplanet research - the study of complex planetary systems and not just of individual planets.
"Studies of planetary motions in the new system reveal complex gravitational interactions between the planets and give us insights into the long-term evolution of the system."