'Super-Earth' spotted in distant sky
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PARIS (AFP) - European astronomers announced they had found a "super-Earth" orbiting a star some 50 light years away, a finding that could significantly boost the hunt for worlds beyond our Solar System.
The planet was spotted orbiting a Sun-like star, mu Arae, which is located in a southern constellation called the Altar and which is bright enough to be seen with the naked eye, they said.
The so-far unnamed world, which whizzes around mu Arae in just 9.5 days, is the smallest of the estimated 125 so-called extrasolar planets that have been detected so far.
"This new planet appears to be the smallest yet discovered around a star other than the Sun. This makes mu Arae a very exciting planetary system," French astronomer Francois Bouchy was quoted in a statement issued by the European Southern Observatory (ESO).
With few exceptions, the extrasolar planets spotted so far have approximated the size of Jupiter, the giant of the Solar System.
But this latest find is far smaller, with a mass of only 14 times that of the Earth, which puts it in the same ballpark as Uranus for size.
The big difference, though, is that Uranus is an uninhabitable hell, a gassy planet on the far frigid fringes of the Solar System, whereas the new planet appears to be a rocky planet, as the Earth, Mars, Venus and Mercury are, and orbits in a much balmier region.
It has a gassy atmosphere, amounting to about a tenth of its mass, although what this consists of is so far unknown.
The object qualifies "as a 'super-Earth," the ESO said.
Much about this enigmatic world remains to be uncovered, least of all whether it may be habitable.
However, there is the tantalising question as to whether it lies within the "Goldilocks Zone" -- a distance from its star that is not too hot, not too cold, just right.
In this zone, a planet would be close enough to the star to have liquid water -- yet not so close that its oceans would boil away -- and not so far that its oceans would freeze. That is one of the prime conditions for creating and sustaining life, according to a leading theoretical model.
The discovery was made thanks to a highly accurate spectrograph, a velocity-measuring instrument, on the ESO's 3.6-metre (11.7-feet) telescope at La Silla, Chile.
In a separate development, a team of American and Spanish astronomers, the Trans-Atlantic Exoplanet Survey (TrES), said they had found an extra-solar planet using a telescope with just a 10-centimeter (four-inch) diameter.
Telescopes of this size can typically be bought in department stores, so this is a remarkable technical breakthrough in planet-hunting.
The newfound planet is a Jupiter-sized gas giant orbiting a star located about 500 light years from Earth in the constellation of Lyra.
This world circles its star every 3.03 days at a distance of only 6.4 million kms (four million miles), far closer and faster than Mercury is in our Solar System.
To make the find, the astronomers used a network of small, inexpensive telescopes whose finds were then followed up and confirmed by the big lenses of the W.M. Keck Observatory on Hawaii.
Most known extra-solar planets have been found by using the "Doppler method" which measures changes to the composition of a star's light that are caused by the planet's gravitational tug.
In the US case, though, the astronomers looked for possible planets that were "transiting" their star -- that were in other words happened to be aligned between the star and Earth as they pursued their orbit. Such planets can then be detected indirectly because of the amount of light they block as they pass by.
The two findings will be published in leading astrophysics journals.
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