28 light years away … there could be life as we know it

Published on Sunday 13 December 2009 21:52

THREE new planets have been found orbiting a nearby star that is almost identical to the Sun.

The planets, whose masses range from 5.3 to 24.9 times that of the Earth, form a mini-solar system circling the star 61 Virginis which is 27.8 light years away and can be seen with the naked eye.

Astronomers hope to discover even smaller potentially habitable worlds within a few years.

The same international team found a fourth planet orbiting another Sun-like star 84 light years away called 23 Librae.

61 Virginis lies in the constellation of Virgo, visible from both hemispheres. It has 0.96 of the Sun's mass and is only slightly less bright.

Its family of planets were discovered by British, Australian and US astronomers using the Anglo-Australian Telescope in New South Wales, Australia, and the Keck telescope in Hawaii.

The new worlds were identified by measuring the "wobble" effect of their gravity tugging on their parent star, a standard planet-finding technique.

Professor Chris Tunney, one of the astronomers from the University of New South Wales, said: "These planets are particularly exciting. Neptune in our solar system has a mass 17 times that of Earth. It looks as if there may be many Sun-like stars nearby with planets of that mass or less. They point the way to even smaller planets that could be rocky and suitable for life."

The findings on 61 Virginis are to appear in The Astrophysical Journal.

The fourth planet is a Jupiter-sized "gas giant" orbiting 23 Librae in the constellation of Libra. Another planet was found orbiting this star in 2006.

It takes 14 Earth years to circle its star, only slightly more than Jupiter's 12-year orbit. Studied from the same distance, the solar system would probably look similar to 23 Librae. Jupiter has the strongest gravitational effect of all the Sun's planets and would be the easiest to identify via the "wobble" technique.

Hugh Jones, one of the British astronomers, from the University of Hertfordshire, said:

"Compared to the solar system, most extra-solar systems look odd, with planets in very small or very elliptical orbits. In contrast, this new planet has an orbit that is both large and nearly circular – and for the first time we are beginning to see systems that resemble our own."

US team member Dr Paul Butler, from the Carnegie Institute of Washington, said:

"The inner planet of the 61 Virginis system is among the two or three lowest-amplitude planetary signals that have been identified with confidence. It's clear that we'll have an excellent shot at identifying potentially habitable planets around the very nearest stars within just a few years."