|
|
Astronomers have discovered an asteroid orbiting the Sun
at the distance as Neptune. It is first known member of a long-sought population of Neptune Trojans.
This small body, known as 2001 QR322, leads Neptune around
its orbit in such a way as to maintain -- on average --
approximately equal distance from Neptune and the Sun. As
such, it mimics the Trojan asteroids of Jupiter, which
orbit the Sun in two clouds approximately 60 degrees
ahead of and behind Jupiter. The first Jovian Trojan was
discovered in 1906, and approximately 1,560 such objects
are known today. However, until the discovery of
2001 QR322, Trojan-like objects associated with other
giant planets had not been found.
2001 QR322 was discovered in the course of the Deep
Ecliptic Survey, a NASA-funded survey of the outer solar
system that uses the National Science Foundation's
telescopes at Kitt Peak National Observatory near Tucson,
AZ, and Cerro Tololo Inter-American Observatory in Chile.
Astronomers from Lowell Observatory, the Massachusetts
Institute of Technology, the University of California
at Berkeley, the University of Hawaii, the University
of Pennsylvania, and the Large Binocular Telescope
Observatory comprise the Deep Ecliptic Survey team.
The team first detected 2001 QR322 on August 21, 2001,
in deep digital images taken with the 4-meter Blanco
Telescope at Cerro Tololo by Marc Buie, Robert Millis,
and Lawrence Wasserman of Lowell Observatory. However,
several subsequent observations, made with a variety
of telescopes over the past 16 months, coupled with
numerical orbit integrations of the trajectory of the
asteroid, were required to prove that 2001 QR322 is
indeed a Neptune Trojan. The object is estimated to be
approximately 230 kilometers (140 miles) in diameter
and, like Neptune, requires about 166 years to complete
each circuit of its orbit.
"Neptunian Trojans were long suspected to exist and it
is gratifying to finally know that they do," says team
member Eugene Chiang of the University of California at
Berkeley. "The orbit of 2001 QR322 is remarkably stable;
projections of its trajectory into the future reveal
that it can co-orbit with Neptune for at least billions
of years. It is likely that 2001 QR322 is a dynamically
pristine object whose orbital eccentricity and inclination
have been largely unaltered by processes that afflicted
the majority of bodies in the outer solar system."
More info: Deep Ecliptic Survey
|
