23 Dec 2012

Five planets found orbiting star

1:55 pm on 23 December 2012

Astronomers have discovered that one of the closest stars to Earth may have as many as five planets orbiting it, one of which could support life.

Tau Ceti is 12 light years away. The ABC reports scientists have examined 14 years of data and found that some of the planets are similar to Earth.

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

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

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

Since 1995, more than 800 exoplanets have been discovered orbiting stars other than the Sun.

But most are either uninhabitable gas giants or big rocky worlds that swing so close to their star that they are literally roasted.

The Tau Ceti finding was made by astronomers from Australia, Britain, Chile and the United States.

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

Tau Ceti was selected to calibrate the new technique because it is a very stable star.

"Because it's so close, bright and similar to the Sun, it's a particularly valuable target for study," said astronomer Jonti Horner of the University of New South Wales.

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 NSW astronomer Chris Tinny, a co-author on the paper, said 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.