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Nasa planet-hunter set for launch

Nasa planet-hunter set for launch
From BBC - April 16, 2018

The US space agency is about to launch a telescope that should find thousands of planets beyond our Solar System.

The Tess mission will go up on a Falcon rocket from Cape Canaveral in Florida and survey nearly the entire sky over the course of the next two years.

It will stare at stars, hoping to catch the dip in brightness as their faces are traversed by orbiting worlds.

Tess will build a catalogue of nearby, bright stars and their planets that other telescopes can then follow up.

Key among these will be the successor to Hubble - the James Webb space observatory, due in orbit from 2020. Its powerful vision will have the capability to analyse the atmospheres of some of Tess's new worlds, to look for gases that might hint at the presence of life.

James Webb will "tease out the chemical compositions of those atmospheres and look for whatever's there," said Paul Hertz, the astrophysics director at Nasa. "People are very interested in looking for, what on Earth, are bio-signatures, such as methane, carbon dioxide, water vapour and oxygen."

Tess follows in the footsteps of Kepler, a groundbreaking space telescope launched in 2009. It also used the "transit technique" to confirm more than 2,000 so-called exoplanets. But Kepler, for its primary mission at least, only looked at a very small patch of sky, and many of its discoveries were simply too far away or too dim for other telescopes to pursue with further analysis.

The Tess strategy will be different on a number of fronts. First and foremost, it is a wide-field survey.

It has four cameras that will map the sky in segments, dwelling on each one for 27 days at a time before then moving on to the next region.

In 24 months, the Transiting Exoplanet Survey Satellite (TESS) should have sampled 85% of the heavens, taking in some 500,000 stars - many of which will be among the nearest and brightest in the sky.

"We are expecting to find 2,000-3,000 planets that are certainly below the size of our Jupiter and most of them below the size of Neptune; so, the ones that have the potential for being terrestrial, for being rocky," said Jennifer Burt from the Massachusetts Institute of Technology (MIT), which leads the mission.

The interest will be in whether they are orbiting at a distance from their host star that allows for liquid water - a prerequisite for life.

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