Kooky Kuiper-Belt Object

A few weeks ago I learned of a curious discovery out beyond Neptune. The object itself, dubbed 2008 KV42, was no bigger than about 30 miles (50 km) across — no threat to Pluto and Eris as the new king of the Kuiper Belt.

Retrograde Kuiper-belt object
The orbit of 2008 KV42 is tipped up so far it's actually moving opposite the direction of the planets. Click here to view a 3D animation of the orbit (warning: 4½ megabytes).
Canada-France Ecliptic Planet Survey
What caught my attention was the inclination of its orbit: 104°. In other words, the path it takes around the Sun is tilted up and over so much that the motion is more "backward" than "forward." Astronomers sometimes term this a retrograde orbit.

It's the first known retrograde trans-Neptunian object, but it didn't seem like that big a deal at the time. After all, 17 asteroids are similarly headed the wrong way around the Sun.

But today, at a meeting of the American Astronomical Society's Division for Planetary Sciences, I learned that 2008 KV42 might be more archetype than oddball. Brett Gladman, a member of the discovery team, explained that this find could be the "missing link" in a long-running cometary conundrum. (I also learned that he and his observing buddies have nicknamed their find "Drac," because Dracula and other vampires purportedly could walk on walls.)

Gladman, J. J. Kavelaars, and Jean-Marc Petit found it on May 31st while trolling for just such high-inclination objects using the Canada-France-Hawaii Telescope atop Mauna Kea in Hawaii.

Comets follow one of three general paths as they plunge toward the Sun. Jupiter-family comets glide in close to the major planets' orbital plane. Most eventually encounter Jupiter and become trapped in tighter, short-period paths around the Sun. The thinking goes that they must originate either from the "classical" Kuiper Belt, a loose disk of bodies that lurk from Neptune's orbit out to about 55 astronomical units (a.u.), or from what are termed "scattered-disk objects," which have eccentric but low-inclination orbits.

image of 2008 KV42
The Gemini South telescope in Chile recorded 2008 KV42 as a a 23rd-magnitude blip in southwestern Hercules. It's currently some 3 billion miles (4½ billion km) from the Sun.
Univ. of British Columbia
Nearly isotropic comets, meaning they come screaming in from pretty much any direction, originate in the outer Oort cloud at least 10,000 a.u. from the Sun. Finally, Halley-type comets, named after the most famous ice ball of them all, have orbits that are highly inclined and often retrograde (as Halley's is).

Despite their best efforts, dynamicists have yet to puzzle out how the Halley-types ended up so skew to the rest of the solar system. Computer models that simulate long-term orbital evolution haven't been able identify a source region in either the Kuiper Belt or the more distant Oort cloud.

Gladman has a hunch that 2008 KV42 might provide some clues. Its average distance from the Sun is 32 a.u. and comes its closest near the orbit or Uranus. So does 2002 XV93, which is inclined steeply at 77°. But Uranus doesn't have enough mass to have yanked these so far up, Gladman says. So, for now, he's headed back to the dynamical drawing board.

5 thoughts on “Kooky Kuiper-Belt Object

  1. Roy RobinsonRoy Robinson

    “…dynamicists have yet to puzzle out how the Halley-types they ended up so skew to the rest of the solar system. Computer models that simulate long-term orbital evolution haven’t been able identify a source region in either the Kuiper Belt or the more distant Oort cloud.”

    The exact origin of any object that interacts with one of our Jovian planets is masked by the random variables of that encounter. It’s likely that a significant number of these objects will end up in a retrograde orbit after the first or subsequent encounters.

    PS: Please remember to proofread your articles before posting them. Sentences such as that quoted above tend to detract from the subject matter. I hope you will excuse my nitpicking; Mrs. Green was a totally ruthless sixth-grade english teacher. 😉

  2. Andy Ferguson

    Nitpicking. I think you mean ‘trawling’ in the sentence ‘..trolling for just such high-inclination objects’

    Definition of “trolling”
    Trolling is the act of purposefully antagonizing other people on the internet, generally on message boards. When done in a moderated internet community, this can result in banning. When done to uptight people such as fundies, this can result in hilarity.

    Not this time though.

  3. Scott

    “When done to uptight people such as fundies, this can result in hilarity.”

    Does that mean lefties are prone to be nutritians because of “free radicals?” 😉

    Can we leave the politico-hate out of an astronomy page? I don’t see this as “uptight,” but I’m tired of seeing labels handed out to strangers like candy. If only…heh…the world would be a better place.

  4. Michael C. Emmert

    Strange they’d name this thing Drac. There’s another strange KBO out there, 2004 XR190, that has a circular orbit that skims the outside of the Kuiper Belt at an inclination of 47 degrees. It was nicknamed “Buffy” after the fictional vampire slayer of television fiction. That might be a good classification, objects that don’t conform to our classification system. And a great naming convention for a class of objects that just doesn’t fit. Just hope we don’t run out of names for things that go bump in the night.

All comments must follow the Sky & Telescope Terms of Use and will be moderated prior to posting. Please be civil in your comments. Sky & Telescope reserves the right to use the comments we receive, in whole or in part, and to use the commenter’s username, in any medium. See also the Terms of Use and Privacy Policy.


This site uses Akismet to reduce spam. Learn how your comment data is processed.