A volunteer who analyzes on-line images for the University of Arizona
Spacewatch program has discovered a 60-to-120-foot diameter asteroid that
will miss Earth by about 1.2 million miles tomorrow, Jan. 22.

While the asteroid is no cause for alarm, its discovery marks a milestone
in a new project that relies on volunteers to spot fast-moving objects,
or FMOs, in Spacewatch images.

Even if asteroid 2004 BV18 hit Earth head-on, it would only create a bright
flash of light in the upper atmosphere, and possibly streaks of light as
asteroid fragments heat to incandescence while they rocket across the sky.
“In other words, a bright meteoric display known as a bolide,” said Robert
S. McMillan, who directs UA’s Spacewatch.

The asteroid appeared in images taken by Spacewatch astronomer Miwa Block
with the 0.9-meter telescope at 1:49 UT on Jan. 19, which is 6:49 p.m. MST
on Jan. 18. Volunteer Stu Megan reviewed the images on the Internet, and
spotted the asteroid’s light trail. Megan is part of a Web-based program
that Spacewatch made public last October through a grant from the Paul G.
Allen Charitable Foundation.

“It’s hard to explain the excitement when you find a fast-moving asteroid,”
Megan said in an E-mail message.

Megan is semi-retired from a 35-year career in information technology and
an amateur astronomer who is interested in finding potentially hazardous
asteroids. A resident of Tucson, he has reviewed close to 6,500 Spacewatch
images during the past three months.

“When I saw (this light trail), it just sat there screaming at me. It was
very, very bright and a perfect length. I knew it could be nothing else.”

Three observatories made follow-up observations of the asteroid, so
scientists at the Minor Planet Center could compute its orbit. The Minor
Planet Center gave Asteroid 2004 BV18 its provisional designation
yesterday.

(A provisional designation is one that’s adopted until the asteroid’s orbit
is known well enough that astronomers won’t lose it.) The center also
published the discovery and follow-up studies in the Minor Planet
Electronic Circular yesterday.

The asteroid is classified as an “Apollo” asteroid because it is on average
slightly farther from the sun than the Earth is, but its modest orbital
eccentricity causes it to occasionally cross Earth’s orbit.

At the time Megan discovered the asteroid, it was six times farther from
Earth than the Earth is from the moon. Seen from Earth, it appeared to move
across the sky at about 6.5 degrees per day, or about the diameter of 13
full moons. At closest approach tomorrow, it will be five times the
distance between Earth and the moon.

Spacewatch operates 1.8-meter and 0.9-meter CCD-equipped telescopes on Kitt
Peak, about 45 miles southwest of Tucson, Ariz. The project studies solar
system dynamics through the movements of asteroids and comets. Spacewatch
also finds potential targets for interplanetary spacecraft missions and
hunts for objects that might pose a threat to Earth.

The 0.9-meter telescope typically takes two-minute-long exposures, and
objects closest to Earth move so quickly through the telescope’s field of
view that they trace a line on the sky image. Objects orbiting farther from
Earth appear to move more slowly, just as an airplane flying at 40,000 feet
appears to move slower than it does at takeoff.

Computer software has a hard time detecting FMO light trails because they
vary greatly in length and direction.

Human observers are still much better than computers at finding FMOs in
Spacewatch images. But the work is too time intensive for on-duty
Spacewatch
observers. So the astronomers have turned to 30 volunteers for help. FMO
project volunteers are based in the United States, Germany, and Finland.

They would gladly accept more.

The only requirements are interest, sharp eyes, and access to a computer
when astronomers are operating Spacewatch telescopes on Kitt Peak. More
details on how to volunteer for the FMO Project are on the Web at
http://fmo.lpl.arizona.edu/FMO_home/index.cfm

“Our reviewers are students, people with full-time jobs, retired — they run
the gamut,” McMillan said. “While our most dedicated volunteers tend to be
members of the amateur astronomy community or at least have a strong
interest and knowledge of astronomy, we have members who have just begun to
climb the learning curve.

“We hope that our Website helps fuel curiosity and participation in science
in general, as well as provide a productive outlet for those eager to apply
their computer skills,” McMillan said.

McMillan’s Spacewatch team protects the privacy of its volunteers,
releasing volunteers’ names only to the Minor Planet Center when
discoveries are to be published.

Astronomers want to study small asteroids to know how many there are, their
spin rates and surface properties, McMillan said.

Spin rate tells observers if the asteroid is a single solid piece or a
loose aggregate of rocks.

The distribution of asteroid sizes tells scientists about the effects of
asteroid collisions during the lifetime of the solar system.

The smallest asteroids are free of regoliths, the blanket of loose dust or
dirt that obscures the bare rock surfaces of larger asteroids. And the
smallest asteroids are useful for studying non-gravitational forces that
work on very long time scales, such as the Yarkovsky Effect, a phenomenon
where heat propels objects through space.

The Spacewatch Project was begun in 1980 at the UA Lunar and Planetary
Laboratory. More information about Spacewatch can be found on the Web at
http://spacewatch.lpl.arizona.edu

Related Web sites

Spacewatch – http://spacewatch.lpl.arizona.edu/

FMO Project and discovery images –
http://fmo.lpl.arizona.edu/FMO_home/index.cfm