Asteroids research published in Nature magazine

Astronomers like Dr. Joe Pollock seldom peer through a telescope anymore when carrying out their research programs. They typically use computer-controlled telescopes to obtain images of celestial objects of interest, images that are then automatically downloaded, often while they sleep or work on other projects.

While the work isn't as glamorous as that of astronomers depicted in the movies, it nevertheless yields valuable information about the cosmic rocks.

Pollock is a professor of astronomy in the College of Arts and Sciences' Department of Physics and Astronomy at Appalachian State University. He also is part of an international research team comprised of scientists from Central and Western Europe, Latin American, Canada and the United States identifying and observing pairs of asteroids called binary asteroids.

Their work has been published in the Aug. 26 issue of Nature magazine.

"It turns out that there are a significant number of asteroids that aren't just a single object, but two and even on occasion three in orbit around one another," Pollock said. He and his colleagues record information related to changes in amount of light reflected from asteroids. Sometimes this indicates the existence of a pair of asteroids that are revolving around each other.

Having access to the telescopes at Appalachian's Dark Sky Observatory as well as remote access to UNC Chapel Hill's PROMPT telescopes in Chile allows Pollock to observe the entire sky.

"When a single, irregularly shaped asteroid spins, the amount of reflective area changes and it appears to change brightness," Pollock said. "When you have two rotating asteroids revolving around one another, the brightness changes are much more complicated but analysis of those fluctuations in light provides important information about the size, mass and density for them. The only other way to get such information is to send a spacecraft to the asteroid."

The astronomers' work is helping determine how binary asteroids form.

Asteroid pairs or binary asteroids are often formed when a single asteroid splits or a conglomeration of pieces held together by gravity breaks apart as the asteroid spins. An increase in the spin speed is caused by the heating and cooling of the asteroid's surface as it passes in and out of sunlight.

"As the asteroid spins faster and faster, eventually it gets to the point that it is spinning so fast a chunk of it breaks off like mud flying off of a tire. That process is referred to as rotational fission," Pollock said.

"In terms of basic knowledge, we can learn a great deal about the formation of the solar system by studying asteroids. On the more practical side, there is also the possibility of mining asteroids in the future. A lot of them are rich in certain valuable minerals. And, perhaps most critically, if one of these asteroids should be found to be on a collision course with Earth, knowing about its mass, composition and structure would hopefully help us to devise ways to effectively deal with it."