Search for a second Earth is on for Kepler telescope

Published on Friday 17 April 2009 22:08

A NEW space telescope has started taking pictures of the star-filled patch of sky where it will soon begin searching for Earth-like planets.

Kepler's first images reveal a vast star field in the Cygnus-Lyra region of our galaxy, the Milky Way.

One picture is ablaze with stars filling the telescope's full field of view. Two others zoom in on targeted regions.

Lia LaPiana, programme executive at the American space agency Nasa's headquarters in Washington DC, said: "Kepler's first glimpse of the sky is awe-inspiring. To be able to see millions of stars in a single snapshot is simply breathtaking."

The 15ft telescope, fitted with British-made light detectors, was launched last month from Cape Canaveral, Florida.

From a vantage point trailing the Earth round the Sun, it will spend three and a half years focused on a patch of sky equivalent to the size of a human hand held at arm's length.

Its mission is to search for unknown planets among more than 100,000 stars. Scientists hope Kepler will find the first evidence of small, rocky planets like the Earth with the right conditions to support life.

Such a planet would lie in the "habitable" or "Goldilocks" zone – an orbital band where temperatures are not too hot and not too cold, but just right to allow the existence of watery oceans, lakes and rivers.

A world with liquid water on its surface may be expected to host living organisms, either primitive or advanced.

Kepler will find planets by detecting almost imperceptible "winks" – the amount of dimming that occurs when a planet moves across the face of a star.

A planet's size and the extent of its orbit can be calculated from the amount of dimming, the length of time between "winks", and the star's mass.

Since the first "exoplanet" outside the solar system was discovered in 1995, more than 340 have been identified.

Most have been detected using ground-based telescopes from the way an orbiting planet's gravity tugs on a star causing it to "wobble".

This "Doppler" technique can find giant planets close to their stars but is not good for locating smaller Earth-like planets. Kepler's "transit" planet-spotting method is more suited.

The full-view image from Kepler shows a 100 square degree portion of sky containing an estimated 14 million stars, including the 100,000 selected as planet-hunting targets.

The two other views focus on just a 1,000th of the full field picture. In one, a cluster of stars about 13,000 light years from Earth called NGC 6791 can be seen. Situated in the other is a star called Tes-2 closely orbited by a known Jupiter-like planet.

Dr William Borucki, the mission's chief scientist based at Nasa's Ames Research Centre at Moffet Field, California, said: "It's thrilling to see this treasure trove of stars. We expect to find hundreds of planets circling those stars, and for the first time, we can look for Earth-size planets in the habitable zones around other stars like the Sun."

Dr James Fanson, Kepler's project manager said: "Our images are road maps that will allow us, in a few years, to point to a star and say a world like ours is there."