Discovery of a Large Kuiper belt object with an Unusual Orbit

A team of astronomers working in Canada, France and the United States have discovered an unusual small body orbiting the Sun beyond Neptune, in the region astronomers call the Kuiper belt. This new object is twice as far from the Sun as Neptune and is roughly half the size of Pluto. The body's highly unusual orbit is difficult to explain using previous theories of the formation of the outer Solar System.

Currently 58 astronomical units from the Sun (1 astronomical unit, or AU, is the distance between the Earth and the Sun), the new object never approaches closer than 50 AU, because its orbit is close to circular. Almost all Kuiper belt objects discovered beyond Neptune are between 30 AU and 50 AU away. Beyond 50 AU, the main Kuiper belt appears to end, and what few objects have been discovered beyond this distance have all been on very high eccentricity (non-circular) orbits. Most of these high-eccentricity orbits are the result of Neptune "flinging" the object outward by a gravitational slingshot. However, because this new object does not approach closer than 50 AU, a different theory is needed to explain its orbit. Complicating the problem, the object's orbit also has an extreme tilt, being inclined (tilted) at 47 degrees to the rest of the Solar System.

http://www.cfeps.astrosci.ca/4b7/index.htm

Paper: astro-ph/0512430

Date: Fri, 16 Dec 2005 03:27:48 GMT (78kb)

Title: Discovery of a low-eccentricity, high-inclination Kuiper belt object at
58 AU

Authors: R. L. Allen, B. Gladman, J.J. Kavelaars, J-M. Petite, J. Wm. Parker,
P. Nicholson

Comments: 3 figures, submitted to ApJL
\\
We report the discovery of the first trans-neptunian object, designated 2004
XR190, with a nearly-cirular orbit beyond the 2:1 mean-motion resonance.
Fitting an orbit to 23 astrometric observations spread out over 12 months
yields an orbit of a=57.2\pm0.4, e=0.08\pm0.04, and i=46.6 deg. All viable
orbits have perihelia distances q>49 AU. The very high orbital inclination of
this extended scattered disk object might be explained by several models, but
its existence again points to a large as-yet undiscovered population of
transneptunian objects with large orbital perihelia and inclination.

\\ ( http://arXiv.org/abs/astro-ph/0512430 , 78kb)