Nasa has got its cheque book out again – this time to back plans for a new space telescope powerful enough to discover planets like Earth and even signs of alien life.

The $3 billion New Worlds Observer will be able to spot oceans, continents and even clouds on small rocky planets, say scientists.

Its “eye” will be a four-metre wide mirror gathering light from stars many light-years away – it will collect nearly three times as much light as the 2.4-metre mirror on the Hubble space telescope.

The NWO will feature a 50-yard wide, daisy-shaped plastic “sunshade” with petals made from black plastic like that used for rubbish bags. It will block the brilliant light from the distant stars, shielding their overpowering glare and allowing the telescope to observe any planets in orbit around them.

The imaginative project is the brainchild of astronomers led by Professor Webster Cash, of the University of Colorado, in Boulder. Nasa have awarded them $1 million to allow plans for the telescope to be advanced.

As well as observing features on other rocky worlds like Earth, the telescope’s instruments will be able to detect signs of life, or biomarkers, such as methane, oxygen and water. Last week, Nasa scientists revealed that as many as 60 per cent of nearby stars like the Sun could have terrestrial-type planets. And an international team used a technique called OGLE to discover a new solar system that they say most resembles our own.

The telescope and its 50-yard-wide starshade would launch into an orbit roughly 1 million miles from Earth. The parasol would then unfurl and be steered by thrusters into the lines of sight of nearby stars which are thought likely to have planets.

Professor Cash said: “This observatory can be built today with existing technology.” He believes he could have the telescope ready for launch in 2017.

His colleague, astronomy research assistant Julia DeMarines told Boulder’s The Campus Press: “What else bigger could there be than finding life on another planet? I think this will make people feel less alone.”

Picture: An artist’s impression of how the telescope will work. (William Cash).

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