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Thursday, April 5
The distant object 2000 CR105 takes roughly 3,300 years to loop completely around the Sun. Right now the 200-kilometer-wide body is 53 astronomical units (8 billion kilometers) from Earth, having passed through perihelion in 1965. In this Sky & Telescope diagram by Roger W. Sinnott, the innermost ring denotes the orbit of Jupiter. Click on image for larger view.
To Marc W. Buie (Lowell Observatory), 2000 CR105 was at first just another distant discovery among dozens found during his team's ongoing search for trans-Neptunian objects using 4-meter telescopes in Arizona and Chile. But its uniqueness became apparent when dynamicist Brian G. Marsden started cranking out possible orbits for this 24th-magnitude find. "It was obviously far away, 53 to 55 astronomical units," Marsden recalls, well beyond most objects known to inhabit the Kuiper Belt.
In the months that followed, an international team led by Brett Gladman (Nice Observatory) quietly tracked the dim interloper. Thanks to their year-long pursuit, it's now clear that 2000 CR105 has a highly eccentric orbit that stretches out to roughly 400 a.u. — more than 10 times Pluto's mean distance from the Sun and far larger than that of any known Kuiper Belt object. But more puzzling to dynamicists is the orbit's perihelion distance. At 44.5 a.u. (6.7 billion km), it is well beyond the perturbing influence of Neptune, whose gravity has flung countless other bodies out to the solar system's most distant fringes. So how did 2000 CR105 end up stranded out there?
Gladman and six colleagues offer several possibilities in an article submitted to the journal Icarus and summarized here. According to coauthor Matthew Holman (Harvard-Smithsonian Center for Astrophysics), the orbit of 2000 CR105 is dynamically chaotic and may simply be the consequence of eons of erratic drift. But that's a statistical long shot, so the team has explored other ideas. Perhaps the Kuiper Belt formed with numerous planet-size bodies in its midst, which wreaked orbital havoc before themselves being heaved out of the region. Or Neptune itself may have ventured farther out before settling into its present orbit. And though the notion is highly speculative, a massive perturber may yet await discovery beyond the Kuiper Belt's known boundary. Holman notes that a body the size of Mars 200 a.u. away could easily have escaped detection to date.
Resolving this mystery will take time, but one implication is already clear. Objects like 2000 CR105 should be exceedingly rare, so if others are found then the Kuiper Belt is likely much more massive than currently envisioned.
— J. Kelly Beatty
The paper has been submitted to astro-ph, and is also available via
WWW download as
UNCOMPRESSED POSTSCRIPT (3.8 Mb), at
http://www.obs-nice.fr/gladman/Extended.ps
G-ZIPPED POSTSCRIPT (0.52 Mb), at
http://www.obs-nice.fr/gladman/Extgz.ps.gz
ORBIT OF SCATTERED DISK OBJECTS AND 2000 CR105
This figure compares the orbits of the other scattered disk objects
with that we have estimated for 2000 CR105.
This figure shows the orbits of all the known scattered disk objects (SDOs)
as well as the much larger orbit of 2000 CR105 (in red).
The SDOs are objects which are on large looping orbits; the most developed
theories for the creation of the scattered disk produce these orbits by
gravitational scattering due to Neptune, which hurls them out to external
orbits which take hundreds of year to circulate around the Sun.
Numerical calculations have shown that some of the objects can rest in
this state for the 4.5-billion year lifetime of the Solar System.
The first recognized SDO was 1996 TL66, discovered by Luu et al. in 1996
(reprint in pdf format available on the www).
About two dozen such SDOs are now known, many of them have been discovered
and tracked by
C. Trujillo et al.
The figure shows that 2000 CR105 journeys far from the Sun, several times
further than the other SDOs.
There are long-period comets that journey much farther away towards the
Oort cloud.
The interesting facet of CR105's orbit is NOT its large size, but rather
the fact that its perihelion (distance of closest approach to the Sun) is
larger than any other known Solar System object.
This figure shows a dot at the perihelion position of each of the SDOs
plotted in the previous diagram, marking the point of closest solar approach.
Only the orbit of 2000 CR105 is shown, and is dotted when the orbit is below
the plane of the other planets and solid when above (2000 CR105's orbit is
inclined about 20 degrees with respect to the plane of the solar system).
The circle shows the orbit of Neptune, for reference. The straight solid
line is the `line of nodes' of CR105, showing where its orbit intersects
the plane of the planets.
CR105 is currently past it's line of nodes and heading out farther into
deep space to the top left of this plot.
It is striking that this roughly 400-km object would be visible, even
to the most powerful telescopes, for only a tiny fraction of its orbital
period, while it is in the tiny portion near pericenter of its more than
3000-year orbital journey.
Because the perihelia of the SDOs are near Neptune, it is thought
that they are likely to be objects that in the ancient past had a close
pass to Neptune and the planet's gravity `sling-shotted' them out onto large
orbits. Dynamical computer simulations by
Hal Levison
and
Martin Duncan
show in detail how the orbits of this population are distributed.
However, these simulations do NOT produce orbits with PERIHELIA as far
away as 2000 CR105 (although orbits as LARGE do occur).
Simply put,
this is because the objects that are scattered out from Neptune by close
encounters are `close' to the planet at the instant of scattering.
The object will then return to that point after one orbit and only continual
long-term `wandering' of the perihelion due to encounters that are not
as close can allow the perihelion to drift away from Neptune.
The numerical simulations seem to show that it is possible for perihelia to
eventually reach distances as far away as 40 AU. However, CR105's perihelion
if 4.3 AU farther out than that (almost the distance from the Sun to Jupiter!)
Therefore, the simulations do not seem to produce objects like this, and we
believe that for the moment 2000 CR105 should NOT be classed as an SDO.
In the preprint (available above) we discuss various scenarios which could
have produced this fascinating object.
Page maintained by: Brett Gladman Observatoire de la Cote d'AzurURL: http://www.obs-nice.fr/gladman
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This is really interesting stuff. BTW, you have one of the best home pages on Free Republic. Lots of great links and information. Thanks.
4 Posted on 11/21/2001 11:27:17 PST by Zadokite
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.
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