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Sun-like star HD10180 thought to have Earth-sized world

Seven-planet system orbits spaced much like ours

Astroboffins probing the skies with a crafty instrument attached to a mighty telescope high in the Andes have found a sun very like our own - which they believe has a planet of similar size to Earth.

“We have found what is most likely the system with the most planets yet discovered,” says top sky-boffin Christophe Lovis. “We are now entering a new era in exoplanet research: the study of complex planetary systems and not just of individual planets."

The planetary system in question is that of the G-type, main sequence star (ie quite like our own Sun) HD10180, lying 127 lightyears away in the obscure southern constellation Hydrus*, between the Magellanic Clouds as seen from Earth.

HD10180 has now been confirmed to have five big, roughly Neptune-sized planets (say 5 to 13 times as massive as Earth) by measurements from the the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph at La Silla in Chile. In addition, Lovis and his colleagues think that there are probably two more - a hefty Saturn-sized job (65 Earth masses) and one which if confirmed would be the smallest known exoplanet at 1.4 Earth masses.

The discovery of a planet not much bigger than Earth orbiting a star very like the Sun might at first seem to be one of trouser-moistening magnitude: but sadly HD10180a is thought to orbit a mere fiftieth of an Astronomical Unit from its star, meaning that it is far too hot to support life along the same lines as Earth. It is so close to HD10180 that its year lasts barely more than a terrestrial day.

Even so, the discovery of HD10180's planetary system does hold great news for alien-fanciers. The distribution of the system's seven possible planets - only one less than ours, as Pluto was never a proper planet in this sense - seems to follow a principle known as Bode's Law (or the Titius-Bode law), a rough rule predicting the spacing of planets from the Sun.

“This could be a signature of the formation process of these planetary systems,” says Lovis' fellow boffin Michel Mayor.

Though the HD10180 system doesn't appear to offer any homes for life, if Bode's Law applies across the galaxy it ought to mean more Earth-like, water bearing planets and so more aliens to meet/get invaded by and/or new worlds to colonise/invade once that pesky hyperdrive has been mastered.

Lovis and his colleagues' paper can be read by those advanced enough in boffinry to follow it here, free in pdf courtesy of the European Southern Observatory - operator of the HARPS. ®


*The male, or lesser, water snake. Not to be confused with the more famous and much bigger constellation Hydra.

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