Tuesday, December 02, 2003
Nearby Star Has Similar Solar System - Vega
Carl Sagan may have been right: A solar system similar to Earth's appears to orbit the star of his popular book and movie Contact.
The star, Vega, has been scrutinized by researchers at the UK Astronomy Technology Centre at the Royal Observatory in Edinburgh.
They say that its solar system is more similar to ours than any yet discovered.
Vega is the third brightest star in the Northern sky and is easily viewed with the naked eye.
Bluish-white in color, it is just 25 light-years away from the Sun.
Three times the size of the Sun and 58 times brighter, Vega was the first star ever photographed, a feat that occurred in July 1850 at Harvard Observatory in Cambridge, Massachusetts.
The Vega planetary system gained notoriety in Sagan's book and movie Contact, in which it is the source of signals from extraterrestrial intelligence and ultimately the destination of protagonist Ellie Arroway.
Astronomers haven't found extraterrestrial signals from Vega, but using new computer modeling techniques they have increased the likelihood of life in the star's solar system.
The model shows that a faint dust disk around the star is best explained by a Neptune-like planet orbiting at a similar distance to Neptune in our own solar system.
The planet's wide orbit means that there is room within for small rocky planets similar to Earth.
"The irregular shape of the disk is the clue that it is likely to contain planets," says astronomer Mark Wyatt, author of the study. "Although we can't directly observe the planets, they have created clumps in the disk of dust around the star."
The model uses observations from SCUBA, a submillimeter camera operated on the James Clerk Maxwell Telescope in Hawaii.
Observations from the camera show a disk of -180°C dust in orbit around Vega.
The computer model suggests that the Neptune-like planet formed closer to Vega and then moved out to its current orbit over a period of 56 million years, sweeping comets with it and causing the clumpy dust disk.
"Exactly the same process is thought to have happened in our solar system," says Wyatt. "Neptune was 'pushed' away from the Sun because of the presence of Jupiter orbiting inside it."
This suggests that besides having a Neptune-like planet, Vega may also have a Jupiter-like planet.
The model can be tested in two ways, according to Wayne Holland, who made the original observations.
First, it predicts that the clumps in the disk will rotate around Vega once every 300 years, and observations taken a few years from now should show this movement.
Second, it predicts finer detail of the disk's clumpiness that can be confirmed with future telescopes and cameras.
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