[meteorite-list] Kuiper Belt Object Found Possibly As Large As Pluto's Moon
From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 09:43:29 2004
National Optical Astronomy Observatory
RELEASE DATE: July 2, 2001
RELEASE NO: NOAO 01-10
Kuiper Belt Object Found Possibly As Large As Pluto's Moon
Astronomers from Lowell Observatory, the Massachusetts Institute of
Technology, and the Large Binocular Telescope Observatory have discovered an
icy planetary body orbiting the Sun beyond Neptune in the Kuiper Belt roughly
equal in size to Pluto's moon Charon.
"This object is intrinsically the brightest Kuiper Belt Object found so far,"
says Lowell Observatory Director Robert Millis, leader of the survey team.
"The exact diameter of 2001 KX76 depends on assumptions that astronomers make
about how its brightness relates to its size. Traditional assumptions make
it the biggest by a significant amount, while others make it larger by at
least 5 percent."
Assuming a reflectivity (or albedo) of 4 percent, 2001 KX76 would have a
diameter of approximately 1,270 kilometers (788 miles), bigger than Ceres,
the largest known asteroid. For comparison, Pluto's moon Charon has an
estimated diameter of 1,200 kilometers (744 miles).
Earlier this year, a Kuiper Belt Object (KBO) called 20000 Varuna was
announced with an estimated diameter of 900 kilometers, based on a calculated
reflectivity of 7 percent. Applying this albedo to 2001 KX76 gives it a
diameter of roughly 960 kilometers (595 miles).
2001 KX76 was discovered in the course of the Deep Ecliptic Survey, a NASA-
funded search for KBOs being conducted by the Lowell-MIT-LBT team using the
National Science Foundation's telescopes at Kitt Peak National Observatory
near Tucson, AZ, and Cerro Tololo Inter-American Observatory in Chile. The
team spotted 2001 KX76 in deep digital images of the southern sky taken with
the 4-meter Blanco Telescope at Cerro Tololo on May 22 by James L. Elliot of
MIT and Lawrence H. Wasserman of Lowell Observatory.
2001 KX76 is currently at a distance of just over 6.4 billion kilometers
(4 billion miles) from the Sun. Its orbit is inclined by approximately 20
degrees with respect to the orbital plane of the major planets, but the
detailed shape of its orbit remains uncertain. Available evidence suggests
that the newly discovered KBO may be in an orbital resonance with Neptune,
orbiting the Sun three times for each time that Neptune completes four
The brightness and colors of 2001 KX76 have been measured by Elliot, Susan
Kern, and David Osip, all of MIT, with the Raymond and Beverly Sackler
Magellan Instant Camera (MagIC) on the 6.5-meter Magellan Telescope at Las
Campanas Observatory in Chile. The object has a distinctly reddish color
typical of many primitive bodies in the outer Solar System.
"2001 KX76 is so exciting because it demonstrates that significant bodies
remain to be discovered in the Kuiper Belt," Millis explains. "We have every
reason to believe that objects ranging up to planets as large or larger than
Pluto are out there waiting to be found. Until the Kuiper Belt has been
thoroughly explored, we cannot pretend to know the extent or the content of
the Solar System."
The existence of the Kuiper Belt was postulated by J. A. Fernandez and by
M. Duncan, T. Quinn, and S. Tremaine in the 1980s to explain the origin of
short-period comets. These comets move around the Sun in the same direction
as the planets, and are found in orbits that are tipped only modestly with
respect to the ecliptic plane. These researchers showed that short-period
comets could not have originated from the more distant spherical Oort Comet
Cloud as originally believed. They predicted that a second, more flattened
reservoir of "proto-comets" must lie beyond the orbit of Neptune.
The first Kuiper Belt Object was found in 1992 by David Jewitt and Jane Luu
of the University of Hawaii. Since then, astronomers have found over 400
KBOs, but tens of thousands likely remain to be discovered. These objects
are believed to be remnants from the formation of the Solar System, and
consequently are among the most primitive and least-evolved objects
available for study by planetary astronomers.
About one-quarter of the known KBOs have been found by the Deep Ecliptic
Survey Team. Other members of the team are Marc Buie of Lowell and Mark
Wagner of the Large Binocular Telescope Observatory on Mount Graham, AZ.
The Deep Ecliptic Survey was recently awarded formal survey status at
the National Optical Astronomy Observatory (NOAO), assuring that this
reconnaissance of the outer Solar System will continue for the next three
Much more precise measurement of KBO diameters will be possible with NASA's
upcoming Space Infrared Telescope Facility (SIRTF) mission, due for launch
Kitt Peak and Cerro Tololo Inter-American Observatory are part of NOAO,
which is operated by the Association of Universities for Research in
Astronomy (AURA), Inc., under a cooperative agreement with the National
The survey team's research is supported by the NASA Planetary Astronomy
Program through grants to Lowell Observatory, Flagstaff, AZ, and MIT in
NOAO is operated by the Association of Universities for Research in
Astronomy (AURA), Inc. under cooperative agreement with the National
For more information:
NOAO Public Information Officer
(520) 318-8214, disbell_at_noao.edu
Public Affairs Officer
:: :: ::
NOTE: Robert Millis, James Elliot, and Lawrence Wasserman can be reached at
(928) 774-3358 or via e-mail at rlm_at_lowell.edu , jim@MIT.edu , and
IMAGE CAPTION: [http://www.noao.edu/outreach/press/pr01/images/kbo.jpg]
The May 22, 2001, discovery image for the large Kuiper Belt Object 2001 KX76
was produced by combining two exposures from the 4-meter Blanco Telescope at
CTIO in such a way that moving objects appear as red-colored pairs of images.
2001 KX76 is the bright red-cyan pair of dots at the center of the picture.
Non-moving objects, such as stars and galaxies, appear white in the picture.
Credit: Deep Ecliptic Survey Team/NOAO/AURA/NSF
Received on Tue 03 Jul 2001 11:47:26 AM PDT