By
Dr David Whitehouse
BBC News Online science editor
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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
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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
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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."
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