UH astronomers find
new type of asteroid

A space rock in Earth's
front yard may change our view
of collision risks

By Helen Altonn
Star-Bulletin

About 1-1/2 years of work on techniques to detect an asteroid with an orbit entirely within Earth's orbit paid off for two University of Hawaii astronomers.

Planetary astronomer David Tholen and Robert Whiteley, a graduate student, discovered the new type of asteroid during two days of observations in February with UH's 88-inch telescope on Mauna Kea.

However, Whiteley said today, "This particular object actually is lost. It's kind of unfortunate. It's the first one we've seen, and it's impossible to recover it."

Two nights of observations aren't enough to project the asteroid's orbit in August when he and Tholen have more time on the telescope, Whiteley said. "We wouldn't be able to catch up with it. What we need is regular access to telescopes so we can follow these things. The loss of that object is really bad luck."

Tholen points that there is a lot of interest in asteroids that could collide with Earth, "not only in Hollywood but with astronomers who take this seriously."

But most astronomers working on the problem are looking outside the Earth's orbit, he said.

"Suppose you have an asteroid that's inside the Earth's orbit and stays there and comes up and just grazes the Earth's orbit. It could still collide (with Earth), but you won't find it by other folks looking outside the orbit," Tholen said.

Most astronomers look for asteroids directly away from the sun because that's where the objects are the brightest, Whiteley said.

Looking for objects on the daytime side of Earth, as he and Tholen are doing, is difficult, Whiteley said. "We have only a couple of hours at sunset and sunrise to actually look at these things, whereas people doing opposition searches (away from the sun) can basically look all night."

Tholen said their discovery, asteroid "1998 DK36," appears to be passing 750,000 miles from the Earth's orbit. "1998 DK36 is nothing to lose sleep over," he said. "It's the ones we haven't found yet that are of concern."

Tholen and Whiteley observed the asteroid with a specialized camera on the UH telescope.

Tholen recorded images and sent them to Whiteley's computer via the Internet. Whiteley spotted the asteroid on his computer screen while scanning dusk and dawn skies to assess asteroids within Earth's orbit.

The astronomers computed a preliminary orbit of the object around the sun and determined that its farthest point from the sun "appears to be very close to, but slightly inside the orbit of the Earth," Tholen said.