Fifty new exoplanets discovered

Artist's impression of exoplanet Liquid water is considered essential if a planet is to support life

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Astronomers using a telescope in Chile have discovered 50 previously unknown exoplanets.

The bumper haul of new worlds includes 16 "super-Earths" - planets with a greater mass than our own, but below those of gas giants such as Jupiter.

One of these super-Earths orbits inside the habitable zone - the region around a star where conditions could be hospitable to life.

The planets were identified using the Harps instrument in La Silla in Chile.

The new findings are being presented at a meeting called Extreme Solar Systems in Wyoming, US, and will appear in the journal Astronomy and Astrophysics.

Lead author Dr Michel Mayor, from the University of Geneva in Switzerland, said the haul included "an exceptionally rich population of super-Earths and Neptune-type planets hosted by stars very similar to our Sun".

He added: "The new results show that the pace of discovery is accelerating."

Life markers

Of the new finds, a total of five planets have masses that are less than five times that of Earth.

"These planets will be among the best targets for future space telescopes to look for signs of life in the planet's atmosphere by looking for chemical signatures such as evidence of oxygen," said Francesco Pepe, from the Geneva Observatory, who contributed to the research.

HD 85512 The star HD 85512 lies some 35 light-years away and hosts a potentially habitable planet

One of the worlds, called HD 85512 b, is estimated to be only 3.6 times the mass of the Earth.

It is located at the edge of the habitable zone - the narrow strip around a star where liquid water can be present on the surface of a planet. Liquid water is considered essential for the existence of life.

Observations with Harps have also allowed astronomers to come up with an improved estimate of the likelihood that a star such as the Sun will host low-mass planets such as the Earth (as opposed to giants such as Jupiter).

They found that about 40% of such stars have at least one planet less massive than Saturn.

Harps (High Accuracy Radial Velocity Planet Searcher) is a precision instrument known as a spectrograph that is installed on the 3.6m telescope at Chile's La Silla Observatory.

The instrument searches for planets using the radial velocity method. This looks for spectral signs that a star is wobbling due to gravitational tugs from an orbiting planet.

Paul.Rincon-INTERNET@bbc.co.uk

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