Dusty disc may mean other Earths

By Dr David Whitehouse
BBC News Online science editor

Astronomers say they have evidence for Earth-like planets orbiting a nearby star, making it more like our own Solar System than any yet discovered.

The clumps rotate around the star approximately once every 300 years

The star, Vega, is one of the brightest in the sky, only 25 light-years away.

It is three times larger than our Sun and, at 350 million years old, much younger as well.

Vega has a disc of dust circling it, and at least one large planet which could sweep debris aside allowing smaller worlds like Earth to exist.

The analysis, by astronomers from the Royal Observatory, Edinburgh, is published in The Astrophysical Journal, and is based on observations taken with one of the world's most sensitive cameras.

The device, the Submillimetre Common-User Bolometer Array (Scuba), is attached to the James Clerk Maxwell radio telescope in Hawaii.

Computer model

Its detailed images of Vega and its environment confirm the presence of a disc of very cold dust (-180C) in orbit around the star.

New computer modelling techniques show that structure seen in the disc can be best explained by a Neptune-like planet orbiting at a similar distance to Neptune in our own Solar System and having similar mass.

The disc contains a Neptune-like planet

The wide orbit of the Neptune-like planet means that there is plenty of room inside it for small rocky planets similar to the Earth.

"The shape of the disc is the clue that it is likely to contain planets," says Mark Wyatt of the Royal Observatory, Edinburgh.

"Although we can't directly observe the planets, they have created clumps in the disc of dust around the star."

If this is the case then it may mean that Vega has a planetary system like our own.

Subject to test

The Vega system may have evolved a similar way to our Solar System with gas giants such as Neptune forming close to the Sun, and then being pulled out to their current orbits by gravitational interactions with their neighbours.

During this process such giant planets suck in all the debris that would otherwise pound young planets, allowing life to develop more easily upon them.

The idea can be tested in two ways as Wayne Holland, who made the original observations, explains: "The model predicts that the clumps in the disc will rotate around the star once every 300 years.

"If we take more observations after a gap of a few years we should see the movement of the clumps.

"Also the model predicts the finer detail of the disc's clumpiness which can be confirmed using the next generation of telescopes and cameras."