Planet 17,000 Light-Years Away Revealed

Lens effect reveals distant world

April 16, 2004
By Dr David Whitehouse
BBC News Online science editor


The most distant known planet has been detected orbiting a star some 17,000 light-years away, say astronomers.

It was found because, as seen from the Earth, it passed in front of a more distant star and its gravity amplified the background star's light.

This "gravitational lensing" effect was predicted by Albert Einstein in his General Theory of Relativity.

Nasa says that the way the background star's brightness changed revealed the existence of the planet circling it.

The gravitational field of a foreground star bends and focuses light from a background star, like a lens in a telescope, but only if the foreground and background star are precisely aligned.


PREDICTION COME TRUE

The newly discovered planet is deep in the constellation of Sagittarius and orbits a dim so-called red-dwarf star.

The planet is probably about one-and-a-half times the mass of Jupiter and orbits its star about three times farther apart than the Earth orbits the Sun.

A gravitational lens in action
The discovery was made possible through cooperation between two teams of astronomers: Microlensing Observations in Astrophysics (Moa) and the Optical Gravitational Lensing Experiment (Ogle).

Dr Bohdan Paczynski of Princeton University who first proposed using the gravitational lensing technique to search for planets around other stars is delighted by the discovery.

"I'm thrilled to see the prediction come true with this first planet detection through microlensing," he said.

He added that he and his colleagues believe that over the next few years the method may lead to the discovery of Neptune-sized and even Earth-sized planets around distant stars.

http://news.bbc.co.uk/2/hi/science/nature/3631889.stm