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Fresh bid to see exo-Earths

Improved instruments and a telescope windfall could aid the search for extrasolar life.

Ron Cowen
22 January 2013

As NASA’s Kepler spacecraft finds signs that the Galaxy is teeming with Earth-sized planets, astronomers are renewing a stalled quest: to gather light directly from an Earth twin and teaseit apart for the chemical signatures of life. That is not possible with current techniques, which find planets indirectly; and in 2006, NASA cancelled a mission that might have had a chance at doing so. The Terrestrial Planet Finder (TPF) would have used either an array of small telescopes or one giant, 8-metre mirror to capture planetary light. Now a new generation of instruments is raising hopes that a smaller, cheaper space tele­scope could do the job.

The TPF cancellation was “a big blow”, says Olivier Guyon, an astronomer at the University of Arizona in Tucson who also works on Japan’s Subaru Telescope in Hawaii, “but it also felt like a challenge to see what we could do with smaller tele­scopes”. Guyon and others are hoping to meet that challenge with advanced corona­graphs: telescope devices that mask starlight like an artificial eclipse, allowing nearby planets that would otherwise be obscured by the star’s glare to be seen (see ‘Blot out the light’). NASA is exploring the idea of putting a coronagraph on one of a pair of 2.4?metre space telescopes donated to the agency by the National Reconnaissance Office, which operates the US fleet of spy satellites (see Nature 490, 16–17; 2012). Although a telescope that size — the same as the Hubble Space Telescope — would be hard-pressed to gather light from Earth-sized planets, it could image and take chemical spectra from planets the size of Jupiter and possibly even smaller than Neptune.

Read more: Fresh bid to see exo-Earths : Nature News & Comment.

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