Old equipment finds big asteroid nearby - students Timothy Spahr and Carl Hegenrother identify the largest known asteroid to pass the Earth at a distance less than 450,000 kilometers - Astronomy - Brief Article

Instead of using expensive, solid-state light detectors, the two students had to rely on photographic film. And instead of looking in the plane of the solar system, where most asteroids are thought to reside, they pointed their small telescope 35#161# out of the plane.

Nonetheless, with a 16-inch telescope atop Mount Bigelow north of Tucson, Timothy Spahr and Carl Hegenrother have discovered what appears to be the largest known asteroid to have come within 450,000 kilometers of Earth. Only five recorded asteroids have come closer.

"This asteroid wouldn't destroy civilization if it hit Earth, but it sure would mess things up," says Spahr, now a graduate student at the University of Florida in Gainesville. He identified the asteroid, dubbed 1996 JA1, on May 15 from film taken 2 days earlier. Hegenrother and the students' supervisor, Steve Larson, both of the University of Arizona in Tucson, confirmed the finding with a telescope on Arizona's Kitt Peak. They describe the discovery in a May 18 circular of the International Astronomical Union. Scientists estimate that 1996 JA1 has a diameter of 300 to 500 meters. In contrast, each of the five asteroids known to have passed closer to Earth was 5 to 100 meters across.

"We were told when we started this project that we would never find anything interesting," says Hegenrother. "But this object would not have been found had we been looking along the [plane of the solar system] with everyone else."