Kepler, a sophisticated space telescope, blasted off from Cape Canaveral, Florida, in the early hours of the morning, and separated from its carrier, a Delta II rocket, nearly 450 miles above the earth.

Its three and a half year mission is to find – if they exist – other planets capable of sustaining life in the Milky Way galaxy. If it succeeds it will be a sensational discovery in space exploration, raising the possibility that there are places out there where life could evolve. If it fails, however, scientists admit it will effectively symbolise "the end of Star Trek" for the time being.

"It's not just a science mission, it's a historic mission," said Ed Weiler, associate administrator for NASA's Science Mission Directorate.

Kepler, named after the German 17th century astrophysicist, will not be looking for signs of life. That job remains for future space missions.

Instead, the telescope will spent its entire mission staring at the same point in the hope of finding a planet in the so-called "habitable zone" around a star, where scientists believe water could be present. It will aim to detect tiny fluctuations in the brightness of stars, which would indicate a planet passing in from of them. That in turn will allow scientists to calculate and orbit of the planet, and whether it has the potential to sustain life.

Its fixed gaze will be through lenses so powerful that they can detect from space a human being on Earth turning on and off an outside light at night. That will enable it to scan up to 100,000 stars near the Cygnus and Lyra constellations, which are between 600 and 3,000 light years away.

Every 30 minutes it will record the brightness of the stars using a 95 megapixel camera, which is around ten times the capacity of a professional photographer's camera. It is the largest and most powerful piece of photographic equipment ever sent into space. "Finding Earth-sized planets is like trying to detect a very tiny flea." said Kepler's project manager, James Fanson.

At a cost of almost $600m (£425m), it is Nasa's first mission in search of Earth-like planets. Those which would be capable of supporting life would be expected to orbit suns similar to ours, at exactly the right distance and temperature for life-sustaining water to exist.

Astronomers have found more than 300 planets orbiting other stars, but they are mainly inhospitable gas-based giants similar to Jupiter.

At best, scientists hope Kepler will discover relatively small planets that are neither too hot nor too cold, and are rocky – similar to Earth.

"If we find that many, it certainly will mean that life may well be common throughout our galaxy, that there is an opportunity for life to have a place to evolve," Kepler's principal investigator, William Borucki, said.

"If none or only a few of these planets are found, it might suggest that habitable planets like Earth are very rare and that Earth may be a lonely outpost for life. In fact, it will be the end of 'Star Trek'."

by:telegraph