The planet is 3.6 times larger than Earth and orbits its star in under 60 days, a distance that puts it within the star's habitable zone - where liquid water can exist on the surface under the right conditions.

The planet, known as HD85512b, is about 36 light years from Earth, in the constellation Vela. It is only the second planet found outside our solar system where the environment may be just right to host life.

A planetary astronomer, Simon O'Toole, said highly sensitive instruments meant astronomers were finding extrasolar planets more rapidly than ever.

''And we getting closer to the holy grail of finding another Earth,'' Dr O'Toole, from the Australian Astronomical Observatory, said.

But the technology to determine whether the Vela planet was rocky, like Earth, and detect whether it had an atmosphere - two other necessities for life - was still a while away, he said.

Of the 50 exoplanets discovered, the largest number ever announced at once, 16 were super-Earths, with a mass between one and 10 times that of Earth.

The findings are the result of an eight year observation program run by the European Southern Observatory using a sensitive spectrograph, called the High Accuracy Radial Planet Searcher (HARPS), attached to a telescope in Chile.

The planet-hunting instrument is able to detect a wobble in a star's motion as a planet circles around it. The speed of the wobble indicates a planet's gravity pulling at the star.

Close to 600 exoplanets have been found, with a further 1200 candidates identified by NASA's Kepler spacecraft, which sources exoplanets by observing changes in a star's brightness as a planet crosses in front of it.

The planet hunter and lead HARPS investigator, Michel Mayor, said the instrument's discoveries had exceeded all expectations, locating a rich population of super-Earths and Neptune-type planets hosted by stars like to the sun.

''The detection of HD85512b is far from the limit of HARPS and demonstrated the possibility of discovering other super-Earths in the habitable zones around stars similar to the sun,'' Professor Mayor, of the University of Geneva, said.