Photos of a star called Beta Pictoris show new evidence that a planet has formed in orbit of the young star just 63 light-years from the sun.
Sally Heap, a NASA astronomer, said Thursday that the photos show a wispy bulge that could be the gravitational wake of a large planet churning through the dusty disk that surrounds the star.The pictures, taken by a new camera on the Hubble Space Telescope, focus on the protoplanetary disk, sort of a halo of dust and gas that rotates around the star. Instead of having a smooth flow, the disk has a dramatic warp in one quadrant.
Heap said the bulge could only be shaped by the orbital path of a large planet, perhaps one many times larger than Jupiter, the largest planet orbiting the sun.
"We can't see it (the planet), but we can see the effects of its gravitational pull," Heap said at a news conference by the American Astronomical Society.
Radio astronomy studies have suggested the presence of planets around more than a dozen other stars, but this is the strongest evidence yet in visible light of a possible planet. It adds to an earlier study that suggested planets were forming about Beta Pictoris.
To make a photo search for a planet, astronomers had to block light from the very center of Beta Pictoris. This allowed the Hubble to photograph the star's disk.
Heap said the picture clearly shows that one side of the disk swirls outward in a bulge "that could only be formed by a planet."
Beta Pictoris has long fascinated astronomers because it is about eight times brighter than the sun, apparently very young and 63 light-years from the sun, which is relatively close to the solar system. A light-year is the distance light travels in a year - about 6 trillion miles.
Heap said the star is 20 million to 100 million years old, just a fraction of the sun's 4.5 billion to 5 billion years.
But despite the young age, said Heap, the star apparently already has planets forming. This suggests, she said, that planets form very early in the life of a solar system.
"When we study Beta Pictoris, it tells us things about how solar systems, such as ours, formed," she said.
The case for a planet about the star is strengthened by a study that found the dust in the Beta Pictoris disk is of the same composition as the dust found in comets in the solar system.
Sergio Fajardo-Acosta of the University of Denver said the dust suggests that Beta Pictoris has a dense population of comets, just as the solar system is thought to have had early in its formation.
One major difference between the sun and Beta Pictoris, however, is life expectancy.
Heap said that Beta Pictoris will probably burn out after about a billion years, far sooner than the sun's expected life of about 10 billion years. This means that even if planets do form about the star, it is unlikely they ever will develop the complex life forms of an Earth-like planet, the astronomers said.