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Saturday, September 26, 1998 Published at 07:47 GMT 08:47 UK


Sci/Tech

Planets doubling up

The double star showing planet forming material

There may be more planets in space than astronomers had realised. Our science editor Dr David Whitehouse reports

Many scientists had believed that stable planetary systems could form only around single stars like our own Sun.

But observations, published in the journal Nature, challenge that view, suggesting there may be more planets in the universe than had been thought.

Astronomers using Very Large Array (Vla) radio telescopes found two planet-forming disks around each of a pair of stars that orbited each other.


[ image: The Vla in New Mexico]
The Vla in New Mexico
Luis Rodriguez, of the National Autonomous University in Mexico City, who led researchers, said: "Most stars in the universe are not alone, like our Sun, but are part of double or triple systems.

"So this means that the number of potential planets is greater than we realised."

Researchers used the Vla to study a stellar nursery - a giant cloud of gas and dust - some 450 light years away in the constellation Taurus. Here stars the size of the Sun or smaller are being formed.

They aimed at one particular object, believed from previous observations to be a very young star.

Observations showed it was in fact not a single young star but a pair of them, separated only slightly more than the distance between the Sun and Pluto - about three billion miles.

Surprising sight

Importantly, the Vla images show that an orbiting disk of dust, extending out about 800 million miles surrounds each star in the pair. Such dusty disks are believed to be the material out of which planets form.

Planet-forming disks are seen around single stars, but the newly-discovered disks around the stars in the double star system are about 10 times smaller.

It indicates that the disks still can survive in such a close double-star system, something that astronomers had not thought possible.

"It was surprising to see these disks in a binary system with the stars so close together," said Mr Rodriguez.

"Each of these disks contains enough mass to form a solar system like our own," added David Wilner of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts.



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