NASA'S NEW LAUNCH

An unmanned Nasa mission to search the sky for Earth-like planets with the potential to host life has launched from Cape Canaveral in Florida.

The Kepler telescope will orbit the Sun to watch a patch of space thought to contain about 100,000 stars like ours.

It will look for the slight dimming of light from these "suns" as planets pass between them and the spacecraft.

Controllers took their first opportunity to launch the probe, at 0349GMT (2249EST) on 7 March.

Kepler blasted off atop a Delta II rocket from Cape Canaveral Air Force Station.
Kepler will use the largest camera system ever launched into space. "This is a historical mission; it's not just a science mission," said Dr Edward Weiler, Associate Administrator for the Science Mission Directorate at Nasa.
The orbiting observatory can register changes in brightness of only 20 parts per million.





"I maintain that it really attacks some very basic human questions that have been part of our genetic code since that first man or woman looked up into the sky and asked the question: 'are we alone?'."

Equipped with the largest camera ever launched into space, it is the first mission designed to find rocky worlds orbiting Sun-like stars. Planets located in a warm zone - known as the habitable zone - might host liquid water on their surfaces.

And where there is liquid water, scientists argue, there is at least the potential for life.

'Flea in headlights'

Of the 300-plus extrasolar planets discovered to date, only a handful are thought to be rocky like the Earth, and none are Earth-mass. The vast majority are gas giants like Jupiter or so-called ice giants like Neptune.

This is thought to be due to the technological limitations of current telescope technology, rather than a lack of Earth-mass planets in our galaxy.

Kepler will detect the periodic dimming of stars caused by transiting planets. THE KEPLER SPACE TELESCOPE

Will study more than 100,000 suns Continuously for 4 to 6+ years Tuned to see Earth-size planets Will target the habitable zone Also see Mars to Jupiter sizes First results within 3 months

Some star systems are oriented in such a way that their planets cross in front of their stars, as seen from Earth's point of view. During these transits, the planets cause their star's light to slightly dim, or wink. The orbiting observatory can register changes in brightness of only 20 parts per million.

"If Kepler were to look down at a small town on Earth at night from space, it would be able to detect the dimming of a porch light as somebody passed in front," said James Fanson, Kepler project manager at Nasa's Jet Propulsion Laboratory in California.

He commented: "Trying to detect Jupiter-size planets crossing in front of their stars is like trying to measure the effect of a mosquito flying by a car's headlight.

"Finding Earth-sized planets is like trying to detect a very tiny flea in that same headlight."

William Borucki, Kepler chief scientist from Nasa's Ames Research Center in California, said: "We will monitor a wide range of stars; from small cool ones, where planets must circle closely to stay warm, to stars bigger and hotter than the Sun, where planets must stay well clear to avoid being roasted."