NASA retires planet-hunting Kepler space telescope

The telescope that found thousands of distant worlds over the past decade has run out of fuel. Kepler‘s successor has already embarked on a mission to add to the telescope's tally of planets that could support life.

NASA on Tuesday announced the demise of its elite planet-hunting telescope just a few months shy of its 10th anniversary.

The Kepler space telescope that found thousands of planets beyond our solar system and boosted the search for worlds that might support life has run out of fuel, NASA said.

The spacecraft, which is currently orbiting the sun 94 million miles (156 million kilometers) from Earth, will drift further from our planet when mission engineers turn off its radio transmitters, the US space agency said.

"While this may be a sad event, we are by no means unhappy with the performance of this marvelous machine. Kepler's nine-and-a-half year flight was more than twice the original target," Charlie Sobeck, project system engineer at NASA's Ames Research Center in California, told reporters on a conference call.

The $700 million mission led to the discovery of more than 2,600 of the roughly 3,800 exoplanets or planets outside our solar system that have been documented in the past two decades.

Several of them are rocky and Earth-sized in the so-called Goldilocks or habitable zone of a star — an orbit where temperatures are neither too cold nor too hot, but just right for the existence of water, which is considered a key ingredient for life.

"Basically, Kepler opened the gate for mankind's exploration of the cosmos," William Borucki, Kepler's now-retired chief investigator, told reporters.

Second life

The mission was almost over in 2013 when the telescope's positioning system broke down. But scientists found a way to keep it operational.

"It was like trying to detect a flea crawling across a car headlight when the car was 100 miles away," said Borucki said.

The resurrected mission became known as K2 and yielded 350 confirmed exoplanets.

Borucki said his favorite exoplanet spotted by the telescope was Kepler 22B, located more than 600 light years from Earth. It is a possible "water world" the size of Earth perhaps covered with oceans and with a water-based atmosphere.

Kepler's successor

Kepler was succeeded by NASA's Transiting Exoplanet Survey Satellite, or TESS, which was launched in April.

The washing machine-sized telescope will scan almost the entire sky for two years in the search for more worlds circling stars beyond our solar system that could harbor life.

Tess's range of observation is 400 times larger than that of Kepler, and unlike its predecessor, Tess will not always be looking at the same section of the sky. It will divide the heavens into 26 sectors. The craft will monitor each of those sectors for 27 days.

Tess will mainly scout for planets in the Goldilocks zone of a star.

NASA's bigger, more powerful James Webb Space Telescope, due to launch in another few years, will then study the most promising candidates to find out whether they could support life.