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Astronomers detect nearest Earth-like neighbour

tau Ceti new planets

The new technique doubles the sensitivity of detecting planets using the radial velocity method (Source: J. Pinfield/RoPACS network/University of Hertfordshire)

Nearest neighbours Scientists have been surprised by the unexpected discovery of a nearby solar system using a new experimental technique.

The system of five planets ranging in size from two to six times the Earth's mass orbiting the Sun-like star Tau Ceti, just 12 light years away.

The discovery, reported in the journal Astronomy and Astrophysics, will make it easier to find smaller more Earth-like planets orbiting other stars.

As well as being the nearest system to the Earth with a Sun-like star, it includes one planet of about five Earth masses, orbiting in the star's habitable zone, where liquid water could exist on the surface.

The new planetary system was discovered using the radial velocity method, which detects the wobble in a star caused by the gravitational pull of an orbiting planet.

Unexpected find

One of the paper's authors, University of New South Wales astronomer, Dr Jonti Horner, says the discovery was serendipity.

"Mikko Tuomi, from the University of Hertfordshire, was looking at new ways to model data to remove unwanted interference and noise generating false signals in our equipment," says Horner.

"This noise can be caused by vibrations in the star due to effects like starquakes and turbulence, as well as instabilities in the equipment itself."

Tau Ceti was selected to calibrate the new technique because it's a very stable star, which after 14 years of study, showed no signs of a planetary system.

"Because it's so close, bright and similar to the Sun, it's a particularly valuable target for study," says Horner.

Once all the noise had been accounted for using the new modelling techniques, astronomers detected a signal indicating the presence of a planetary system.

University of New South Wales astronomer Professor Chris Tinny, who is a co-author on the paper, says the new technique doubles the sensitivity of detecting planets using the radial velocity method.

Astronomers believe the proximity and brightness of Tau Ceti will allow them to eventually study the atmospheres of the planets in the system.

Gliese 667C

The radial veolcity technique has also been used in the discovery of three new planets orbiting in the habitable zone of a red dwarf star called Gliese 667C.

The research by astronomer Professor Emeritus Philip Gregory of the University of British Columbia, includes a planet of just over two Earth masses making it the lowest mass planet ever detected in a habitable zone.

Gliese 667C is part of a triple star system about 22 light years from Earth in the constellation of Scorpius.

Gregory discovered six planets orbiting the red dwarf which circles about 30 billion kilometres out from a pair of larger Sun like stars named Gliese 667A and B.

Since 1995, more than 800 exo-planets have been discovered orbiting stars other than the Sun.

Tags: planets-and-asteroids, stars