Discovery of the retrograde trans-neptunian object 2008 KV42.

Orbit paths (looking along the plane of the solar system) of the retrograding 2008 KV42 and some other outer solar system objects

The CFEPS project team announces the detection and orbit determination of the first ever trans-neptunian object known to orbit backwards around the Sun. [Contact details at the bottom of this page.]

Link: Technical Summary

Link: Animation and Images Page

The trans-Neptune region of the Solar System (often referred to as the Kuiper Belt) contains objects whose physical compositions are mixes of ice and rock. Until now, all of the known trans-neptunians (abbreviated TNOs below) circle the Sun in the same sense as the planets, mostly on orbits that look like circles and which are only slightly tilted when compared to the plane in which Neptune orbits. The great majority have tilts less than 20 degrees (Pluto is 17 degrees), and all but one have tilts less than 50 degrees.

COMET CLASSES

The known comets can be divide into three groups, based on the shape of their orbit.

- ‘nearly isotropic’ comets (meaning they are come from all directions). These comets plunge in from the outer Oort cloud from ten-thousand times (or more) the distance from Sun to Earth. They have very large orbits, and cross inside of Jupiter’s orbit.

- ‘Jupiter-Family comets’ which orbit with small tilts. These comets are believed to come from the Kuiper Belt.

- ‘Halley-type comets’ have retrograde and/or highly-inclined orbits, their origin is currently a puzzle. Models trying to produce these from either a Kuiper Belt source or an Oort cloud source have been largely unsuccessful.

The previous record-holder is named 2002 XU93 (discovered by the Deep Ecliptic Survey) with a orbital tilt of 77 degrees.

The CFEPS project, while searching for TNOs on highly-inclined orbits, discovered 2008 KV42 on May 31, 2008 using the Canada-France-Hawaii telescope. Given how bright it is, the object is only about 50 km (30 miles) across. Immediately upon discovery, it was clear that the object was on an unusual orbit, but it required urgent observations from several other telescopes (the MMT on Mount Hopkins, Arizona, and the two telescope in Chile, the Cerro Telolo Blanco telescope and the Gemini South telescope ) to cement the orbit.

The amazing result was that KV42 goes around the Sun backwards compared to the planets and all other trans-neptunian objects. The orbital tilt, or inclination, is 104 degrees (all orbits more inclined than 90 degrees are called retrograde, meaning in the opposite sense).

What’s in a name?

With its `sideways' orbit (see animation), 2008 KV42 is akin to someone who can walk on walls. Because of this, the discovery team has dubbed this object Drac, short for `Dracula', since vampires were alleged to have the power to walk on walls. This is an entirely unofficial temporary name until the orbit can be determined with high precision, at which point a proper name will be assigned according to international nomenclature conventions.

This is an peculiar state of affairs, as finding an object like this was not expected. However, in hindsight this object may offer a link to between certain types of comets and the outer regions of our Solar System.

There ARE some comets which orbit the Sun on retrograde orbits, with comet Halley certainly being the most well-known example.

2008 KV42 is a potential missing link between the known population of Halley-type comets and the unknown source of these comets. Production of KV42 via orbital evolutions from currently known source regions seems extremely improbable. Instead, KV42 may be a `transition object' between a source exterior to the Kuiper belt and the Halley-type comets closer to the Sun. Recent models of the formation of the inner edges of the Sun’s Oort cloud (the long period comets are thought to originate in the Oort cloud) have indicated where the source of objects like 2008 KV42, and thus the Halley type comets, may be located: beyond Neptune’s orbit. Direct observations of the source region will be extremely challenging.

For further information contact:

Canada

JJ Kavelaars, Hertzberg Institute of Astrophysics.

jjk@hia.nrc.ca (250) 363-8694

Brett Gladman, University of British Columbia.

gladman@astro.ubc.ca. (604) 822-6244.

France

Jean-Marc Petit, Centre National de la Recherche Scientifique.

petit@obs-besancon.fr (33) 3 8166 6929

United States

Lynne Jones, University of Washington, Seattle.

ljones@astro.washington.edu (206) 795-4755