Sunday, March 18, 2007

Kuiper Belt Detective Work

The Kuiper Belt, a group of smaller, rocky bodies that orbit the Sun past the orbit of Neptune, is providing more clues as to what lurks at the edge of the Solar System--and the dynamics of how these bodies interact. Yahoo News AFP excerpt:

PARIS (AFP) - Astronomers have pieced together the remnants of a mighty collision that smashed apart a planet-sized rock in the Kuiper Belt, on the far-flung fringes of the Solar System.

First identified in the 1950s by Dutch-US skygazer Gerard Kuiper, the disk-shaped belt is believed to be populated by tens of thousands of icy bodies, encircling the Sun beyond the orbit of Neptune.

A team led by Michael Brown of the California Institute of Technology (Caltech) took a close look at the belt's third largest object, 2003 EL61. Nicknamed "Santa" because the team spotted it at Christmas-time, 2003 EL61 is a grey rock so big that it is a contender for the new category of a Solar System "dwarf planet."

Brown describes Santa as "one of the strangest objects in the Solar System," likening its shape to a cigar or an American football that has too little air in it and been stepped on. Flanked by two moonlets, 2003 EL61 measures some 1,500 kilometers (950 miles) across, tumbling over and over at a prodigious rate and pursuing a weird egg-shaped orbit inclined at nearly 30 degrees to the plane at which almost all of the Solar System's objects travel.

Brown's team found five other rocks, measuring between 10 and 400 kilometers (six and 250 miles) across, that they believe were smashed away from 2003 EL61 in the distant past. The cluster shares the same colour and the light they reflect has a signature that suggests they are covered with surface water ice. The paper is published on Thursday in the weekly British journal Nature.

The Kuiper Belt and the asteroid belt, which is located in the gap between Mars and Jupiter, are believed to be rubble left over from the building of the Solar System.

Astronomers have already identified 35 "collisional families" -- clusters formed when their parent rock is whacked -- in the asteroid belt. But this is the first time something similar has been spotted in the Kuiper Belt, and the discovery could shed light on the dynamics that shaped the early Solar System and the surface of Kuiper Belt objects themselves.

Brown is one of the leading authorities on the Kuiper Belt, a region also inhabited by Pluto. His discovery of a big Kuiper Belt object, 2003 UB303 (since renamed 2003 Eris), sparked a fierce debate about the status of planets, leading to Pluto's relegation last year to the status of "dwarf planet" by International Astronomical Union (IAU).

The Kuiper Belt is proving to be a mysterious and fascinating region of the Solar System. Moon-sized objects have been detected at orbits that are highly inclined away from the plane of most of the major planets--a major reason they have evaded detection until recently. It appears we now have reasons to pursue these objects in unexpected areas of the sky, but there are nowhere near enough professional telescopes pointing to these regions. I suspect that the amateur community will step up and eventually make some contributions in this area.

Another resource is one that has been already completed--the recent sky surveys by Hipparcos come to mind. There are thousands of images that can be reviewed and compared to those of previous surveys to see if anything has moved. It appears that Mr. Brown and his team are making some nice progress with this research.

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