University of Virginia Astronomer Greg Black Images Asteroid

February 13, 2008 — University of Virginia research scientist Greg Black, working with astronomers at NASA and other institutions, has captured images of a small asteroid that passed relatively close to Earth on Jan. 29. Astronomers are busily refining their techniques for locating and observing asteroids that could potentially be a threat to our planet.

The object Black observed, Asteroid 2007 TU24, is only about 800 feet in diameter — considered a very small object, and relatively difficult to locate and image in the vastness of space. The object was discovered only a few months prior to passing within 334,000 miles of Earth (our moon is about 220,000 miles away when at its closest point to Earth). 

Astronomers and governments are increasingly concerned that someday a sizable asteroid could hit Earth and cause catastrophic damage to life on the planet. Asteroids have impacted Earth many times in the past and may have caused the extinction of the dinosaurs.

"While we realized that this asteroid was not on a trajectory to hit us, it did give us one of our closest looks at an object this small, which is difficult to observe," Black said. "An asteroid of this size would be dangerous if it hit us."

Black said that understanding the properties of these objects explains their history, how they came to be where they are, where they are going, and, hopefully, how we might deal with a really hazardous one in the future.

"The fact that this asteroid could come this close but was discovered only a few months earlier illustrates the danger of these objects and the need to search for them," he said.

Black obtained images of the asteroid by transmitting a radio signal from the National Science Foundation's Arecibo Observatory in Puerto Rico and then observing the reflection off the asteroid with the Green Bank Telescope in West Virginia (operated by the Charlottesville-based National Radio Astronomy Observatory). The two observatories are among the largest radio telescopes in the world.

The NASA-sponsored Catalina Sky Survey first discovered Asteroid 2007 TU24 on Oct. 11, 2007. NASA detects and tracks asteroids and comets passing close to Earth. The agency's Near Earth Object Observation Program, commonly called "Spaceguard," discovers, characterizes and computes trajectories for these objects to determine if any could be potentially hazardous to Earth.

By Fariss Samarrai