Mysterious deep-space object raises
questions on Solar System's origins
Dec 13 1:38 PM US/Eastern
Astronomers working in Canada, France and the United States said
they had found a small deep-space object, nicknamed Buffy, that
challenges mainstream theories about the evolution of the Solar
System. The rock lies in the Kuiper Belt, the name for the flock of
objects beyond Neptune's orbit that are believed to be leftover
rubble from the Solar System's building phase and are the source
for many comets, the Canada-France Ecliptic Plane Survey (CFEPS)
said.
Measuring between 500 and 1,000 kilometers (300 to 600 miles)
across and taking about 440 years to make just one circuit of the
Sun, Buffy is remarkable not for its size -- around half a dozen
identified Kuiper Belt objects are bigger -- but for its location
and orbital tilt.
"This new object challenges current theories about the history of
the early Solar System," CFEPS said in a press release.
"(...) This new discovery is exciting because it causes us to
rethink our understanding about how the Kuiper Belt formed."
Buffy has an almost perfect circular orbit and encircles the Sun at
an extreme tilt, at 47 degrees to the orbital plane of the planets
as they swing around the Sun.
But it lies in a curious outer region of the Kuiper Belt, on the
dark, bone-freezing fringes of the Solar System.
The theory is that, billions of years ago, this remote community of
rocks, the so-called "extended scattered disk" of the Kuiper Belt,
got their extremely eccentric orbits because of a passing
star.
The star's gravitational pull was enough to give the objects a tug,
pulling them out of a circular orbit but not enough to coax them
away from enslavement to the Sun.
But Buffy is the odd one out -- its almost-perfect orbit and tilt
circular puts a dent in the "star" theory.
One possibility, the discoverers say, is that, in the infant days
of the Solar System, the nascent Neptune lay much closer to the
Sun.
It eventually migrated outwards, causing at least some members of
the Belt's "extended scattered disk" to develop more circular and
tilted orbits, they speculate.
Buffy is the temporary name given by the team for the object, whose
official designation by the Paris-based International Astronomical
Union (IAU) is 2004 XR 190.
Its orbit is in a relatively narrow range of between 52 and and 62
astronomical units (AU) from the Sun (an AU is a standard
measurement, being that of the distance between the Earth and the
Sun, of approximately 150 million kilometers, or 93 million
miles).
By comparison, another "extended scattered disk" member called
Sedna swings out to as far as 900 AU before coming as close to the
Sun as 76 AU.
The Kuiper Belt was first recognised in 1992.
Most of its objects lie in a region that extends from 30 to 50 AU
where there are "at least" 70,000 rocks with a diameter of 100 kms
(60 miles) or more, according to David Jewitt, a specialist at the
University of Hawaii
(http://www.ifa.hawaii.edu/faculty/jewitt/kb.html).
Buffy was first noted by Lynne Allen of the University of British
Columbia, Canada, in December last year as she pored over data from
powerful computers that sift through telescopic images in search of
new celestial sightings.
Because Kuiper Belt objects take so long to go around the Sun, it
takes between one and two years of additional observations to
calculate their orbits precisely.
Further measurements are needed over the next three months for a
fine-tuning of Buffy's orbit.