Mark Wyatt of Edinburgh's Royal Observatory designed a computer model based on observations of a faint disk orbiting Vega, which is three times bigger than the sun and is part of the constellation Lyra, the Harp. Images taken in 1998 by the world's most sensitive submillimeter camera, known as SCUBA, showed extremely cold dust orbiting the star. "The irregular shape of the disk is the clue that it is likely to contain planets," Wyatt says. "Although we can't directly observe the planets, they have created clumps in the disk of dust around the star." The calculations indicate that the formation of a planet similar in size to Neptune--and orbiting the star at a distance comparable to that between Neptune and the sun--can best explain the observed structure of the disk. The model suggests that the planet formed closer to the star and then migrated out to a wider orbit over the course of 56 million years. (In the SCUBA image above, an asterisk marks the position of the star and the orbiting planet is shown as a box.)
As for how well the predictions will hold up, time will tell. "The model predicts that the clumps in the disk will rotate around the star once every 300 years," explains Wayne Holland of UKATC, who worked on the original SCUBA recordings. "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 disk's clumpiness, which can be confirmed using the next generation of telescopes and cameras."