PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (818) 354-5011
Contact: Jane PlattAugust 22, 1996
NEW OBJECT MOVES LIKE A COMET BUT LOOKS LIKE AN ASTEROID
Scientists at NASA's Jet Propulsion Laboratory (JPL), have
discovered a unique and baffling object that may be either an
unusual asteroid or an extinct comet.
The object, designated 1996 PW, was detected by astronomers
using data from the Near-Earth Asteroid Tracking (NEAT) program
that employs a JPL-developed camera mounted on a U.S. Air Force
telescope atop Mt. Haleakala on Maui, Hawaii.
Puzzled scientists are still striving to understand exactly
what object 1996 is and where it came from. "This is a misfit in
the grand scheme of things," according to Eleanor Helin, a
planetary astronomer at JPL and the NEAT principal investigator.
At first look, the object, which has a diameter of about 8
to 16 kilometers (about 5 to 10 miles), appears to be an
asteroid, a chunk of rock that orbits the sun, said Helin.
However, unlike most typical asteroids, which inhabit orbits no
farther out than Jupiter, 1996 PW has a highly elongated, comet-
like orbit that stretches into the vast outer reaches of the
solar system, far beyond Neptune and Pluto. Its orbit has a
period currently estimated at 5,000 years, according to JPL
research scientist Dr. Michael Keesey.
Although 1996 PW is in an orbit resembling that of a long-
period comet, no gaseous emissions or other comet-like activity,
such as a dust come, has been observed, even during its current
closest approach to the Sun, Helin said.
Helin and other astronomers studying the object believe that
this raises the possibility that it was once an active comet, but
is now inert, either because its ice and gases have been stripped
away or because it is covered and insulated by non-volatile
This puzzling object was discovered through a combination of
high-tech telescopes, sophisticated software and human detective
work. The NEAT program at Haleakala, carried out under the
direction of Helin and task manager Dr. Steven Pravdo, also of
JPL, is the world's first fully autonomous near-Earth object
imaging system. It consists of a computer controller and a
highly sensitive CCD camera sensor mounted on a telescope. The
system is designed to discover and track asteroids and comets as
they approach Earth from deep space.
The NEAT system is mounted on the U.S. Air Force's Ground-
Based Electro-Optical Deep Space Surveillance System's one-meter
telescope at the Maui facility.
Observational data from NEAT on the night of August 9
recorded the appearance of 1996 PW, along with similar
observations of 150 more typical asteroids in the belt between
Mars and Jupiter. More observations were made three nights
later. While computer-processing the data at the Smithsonian
Astrophysical Observatory in Cambridge, Massachusetts, Gareth
Williams noticed the object had an unusual apparent motion.
Due to the current position in space of 1996 PW, scientists
will have an excellent window of opportunity to study the object
more thoroughly over the next six months.
Further observations were made at Haleakala by NEAT and by
an Italian amateur astronomer, who learned of the object from the
Minor Planet Center's World Wide Web site. JPL's David
Rabinovitz provided positional and color information on the
discovery. Vital operational work on the incoming data was
handled by JPL's Ken Lawrence, with results reviewed by team
The NEAT camera was installed at the Air Force's Maui
facility in December 1995 to conduct a systematic search for
asteroids and comets that come near Earth. With its short
exposure time and fast electronics, NEAT is able to achieve wide-
sky coverage. It can also detect objects much fainter than was
possible with the photographic Schmidt telescope at Palomar
Observatory in Southern California, which Helin used to conduct
asteroid searches for 20 years.
NEAT was built and is managed by JPL for NASA's Office of
Space Science, Washington, D.C.
The electronic image that led to the discovery of 1996 PW is
available on the NEAT Program's Internet Home Page at: