'Winking' star broadens search for planets

Computer rendering of a dust disk with a protoplanet, red dot, circling a young star.

(CNN) -- Astronomers announced Wednesday they had seen for the first time the periodic eclipse of a young star by a halo of debris, a discovery that could greatly expand the search and study of young planetary systems.

Taking a closer look at a "winking" star, scientists realized it was being eclipsed once almost every 50 days by a knotted disk composed of dust, grains, boulders and perhaps asteroids and protoplanets.

The breakthrough could allow researchers to observe protoplanetary rings as they change over months and years. One such dust disk is thought to have spawned planets in our solar system.

"This team has seen a process involved in planetary formation that's predicted by theory but never been seen before," said Steve Maran, a NASA physicist and American Astronomical Society spokesperson, who was not involved in the study.

"I think this is going to add a whole new dimension of astronomy."

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In the past, scientists viewed circumstellar disks from an "overhead" perspective. In contrast, William Herbst and colleagues watched the star from the "side" and monitored the movement of its lumpy dust ring over several years.

"Basically, the star winked at us," said Herbst. The Wesleyan University professor led an international team which reported the findings in Washington, D.C., at a meeting about exoplanets, or planets outside our solar system.

KH15D in (right) and out (left) of the eclipse phase.

The star, known as KH15D, faded out once every 48 days. But unlike other star eclipses, where stars in binary systems briefly blot out companions, this disappearance act lasted about 18 days.

A companion star could not have caused a black out for that length of time, Herbst and colleagues concluded, only a lumpy string of orbiting debris could.

The periodic eclipses are possibly caused by one or two main clumps, which could indicate the presence of one or more large objects, such as planets or brown dwarfs, the astronomers said.

The new observational method allows scientists to study young star systems much farther away than with current techniques, and to examine in much greater detail the spectral light from the dust rings.

"[It] is going to begin to actually tell us what's in the accretion disk. As far as I know, no one was looking for this," Maran said.

KH15D is about 3 million years old, much younger than our middle-aged sun, which is about 5 billion years old.

In 1997, Herbst and a Wesleyan graduate student discovered the star, which is 2,400 light years away near the picturesque Cone Nebula.

"If we knew it was going to become famous, we would have given it a better name," Herbst said.