About 460 light-years away in the constellation Centaurus, a thick disk of dust swirled around a young star named TYC 8241 2652 1, where rocky planets like our own were arising. Then, in less than two years, the disk vanished.
That's the unprecedented observation astronomers reported. And the same thing may have happened in our own solar system.
Born about 10 million years ago, the TYC 8241 2652 1 system was chugging along just fine before 2009. Its so-called circumstellar disk glowed at the infrared wavelength of 10 microns, indicating it was warm and was close to the star -- in the same sort of region that, in our own sun's neighborhood, gave rise to the terrestrial planets Mercury, Venus, Earth, and Mars. The infrared data reveal that the dust was located as close to its star as Mercury is to the sun.
By January 2010, however, nearly all infrared light from the disk had vanished. "We had never seen anything like this before," says astronomer Carl Melis of the University of California, San Diego. "We were all scratching our heads and wondering what the hell did we do wrong?"
Subsequent observations with infrared satellites and ground-based telescopes confirmed the discovery. He said: "The disk was gone."
Melis and his colleagues reported the mystery online in Nature. But they don't know what caused it. He said there's no way something could eclipse the infrared-emitting disk for more than two years, because such an object would be immense. Furthermore, the star itself didn't fade.
He speculated that a collision between two objects -- perhaps two asteroids or even two planets -- orbiting the star produced the dust grains. Then either the star's light blew the dust out of the planetary system or the dust plunged into the star.
"It's a really interesting mystery," said astronomer Scott Kenyon of the Harvard-Smithsonian Center for Astrophysics, who was not affiliated with the discovery team. "It's sort of amazing to have the dust in one of these disks go away so quickly. It's hard to know exactly what happened."
Astronomer George Rieke, of the University of Arizona in Tucson, said, "This is a whole new insight into the violent processes like the ones that formed the moon and that must be going on where terrestrial planets are forming and first evolving in other planetary systems."
It may offer clues to the violence that surrounded the formation of Earth. In particular, Earth is the only known terrestrial planet with a large moon, whose tides may have helped life advance by pushing it from sea to land; but no one knows how many Earthlike planets sport large satellites. The moon arose when a Mars-sized object hit our planet, a collision that presumably spewed lots of dust into space. The new observations suggest this dust could have disappeared fast.
However, with only one dust-vanishing event ever seen, Melis doesn't know how common the phenomenon is. He said, "We have to wait and see if we ever catch another one."