Five new planets discovered but 'too hot for life'
Published 05/01/2010 | 05:00
A SPACE telescope that hunts Earth-like planets orbiting distant stars has scored its first success, with the discovery of five new worlds beyond the solar system.
The planets detected by the Kepler spacecraft are much larger than Earth, similar in size to Jupiter and Neptune, and as all lie very close to their parent stars are far too hot to harbour life. The find, however, marks an important advance in the search for small rocky worlds like our own.
Kepler does have the sensitivity to find Earth-size planets, said William Borucki, of NASA's Ames Research Centre in California, who leads the mission team.
"These observations contribute to our understanding of how planetary systems form and evolve. The discoveries also show that our science instrument is working well."
Jon Morse, of the astrophysics division at NASA, said: "It's gratifying to see the first Kepler discoveries rolling off the assembly line. We expected Jupiter-size planets in short orbits to be the first planets Kepler could detect. It's a matter of time before observations lead to smaller planets with longer period orbits, coming closer to the discovery of the first Earth analogue."
The results, from data gathered in Kepler's first six weeks of operations, bode well for its galactic census of Earth-like planets in the Milky Way. Over three years, Kepler will inspect 156,000 stars for evidence of rocky planets too small to be detected by ground-based observatories. Astronomers expect it to find hundreds, of which 50 may be orbiting where conditions are neither too hot nor too cold for life.
These are not among the five planets picked up in Kepler's initial sweep. The first, named Kepler 4b, is of similar size and density to Neptune, with a diameter four times that of Earth. The other four are gas giants similar in size to Jupiter, and, like Kepler 4b, orbit very close to stars. "These planets are all hotter than molten lava, and two are hotter than molten iron," Dr Borucki said. "It's certainly no place to look for life."
The gas giants are much less dense than Jupiter-like planets. One, Kepler 7b has a density of 0.17 grammes per cubic centimetre -- about the same as polystyrene. Such low densities are not predicted by standard theories of planet formation. "It's something that theorists will, I'm sure, be delighted to study," Dr Borucki said.
Details of the discovery were announced yesterday at the American Astronomical Society conference in Washington, and published in 'Science'.
The mission should answer questions bearing on whether humanity is alone in the Universe. If habitable planets are common, it would suggest that life is likely to have evolved elsewhere. (© The Times, London)