A visible-light imaging survey of dusty debris disks around other stars, believed to be evidence of collisions between the leftovers of planet formation, has been completed by the Hubble telescope, astronomers say.
Images of debris disks surrounding young stars just 10 million years old and around mature stars as much as 1 billion years old have been collected by the space telescope's comprehensive survey, they say.
Once believed to be simple pancake-like structures, an unexpectedly large variation in their diversity and complexity suggests they're being gravitationally affected by unseen planets orbiting the stars, researchers report in The Astronomical Journal.
"It's like looking back in time to see the kinds of destructive events that once routinely happened in our solar system after the planets formed," says survey leader Glenn Schneider of the University of Arizona.
No two of the disks of dusty material around stars are the same, the researchers found.
"We find that the systems are not simply flat with uniform surfaces," Schneider says. "These are actually pretty complicated three-dimensional debris systems, often with embedded smaller structures."
Some of those substructures may be the result of unseen planets, he added.
Around one star, HD 181327, Hubble observed a massive spray of dust and debris into the outer regions of the dust disk that may be the result of a recent collision between two bodies, researchers say.
"This spray of material is fairly distant from its host star -- roughly twice the distance that Pluto is from the Sun," says co-investigator Christopher Stark of NASA's Goddard Space Flight Center in Greenbelt, Maryland. "Catastrophically destroying an object that massive at such a large distance is difficult to explain, and it should be very rare."
Still, such a suspected planet collision seen in the disk around HD 181327 may be similar to how our Moon was formed from massive amounts of material sheared off the Earth in a collision with another protoplanet.
Of course, the irregularities seen in the dust disks may not all be from planets, the researchers acknowledge.
The disks may have been twisted and warped by interactions with unseen stellar material during the stars' voyages through interstellar space, they suggest.
"Either way, the answer is exciting," Schneider says. "Our team is currently analyzing follow-up observations that will help reveal the true cause of the irregularity."
Only around two dozen debris systems have been captures in images since 1995 because they are usually 100,000 times fainter than their bright anchoring stars, requiring Hubble's capability of performing high-contrast imaging to reveal them.
