[extropy-chat] SPACE: Yet more about KBO 2004 DW
Joseph S. Barrera III
joe at barrera.org
Sat Feb 21 22:51:18 UTC 2004
Here's a very nice article, including this tidbit: "We've traced 2004 DW
back to November 23, 1954, when it was photographed as part of the first
Palomar Sky Survey" and also a bit about getting a better estimate of
its size in the next couple of weeks via the IRAM telescope in Spain.
2004 DW: The largest Kuiper Belt Object?
Astronomers discover an icy world at the fringes of the solar system.
by Francis Reddy
Icy discovery: Is 2004 DW the largest KBO?
Courtesy Chad Trujillo, Gemini Observatory
Posted February 20, 2004
Astronomers at the California Institute of Technology (Caltech) and Yale
University discovered an icy world at the outer fringes of the solar
system on February 17. The object, currently known only as 2004 DW, may
be the largest find in the solar system since 1930, the year astronomers
The object currently lies 4.4 billion miles (7.1 billion kilometers)
away from Earth. Its orbital tilt, about 20.6°, is larger even than that
of Pluto, which itself has an unusually high orbital inclination — far
larger than any other planet.
"We've traced 2004 DW back to November 23, 1954, when it was
photographed as part of the first Palomar Sky Survey," says codiscoverer
Chad Trujillo of the Gemini Observatory in Hawaii. The team, which
included Mike Brown of Caltech and David Rabinowitz of Yale University,
found the new object using the same 48-inch (1.2 meter) Schmidt
telescope on Palomar Mountain, California, used for that survey.
Astronomers at Australia's Siding Spring Observatory also found 2004 DW
on a pre-discovery photograph taken November 8, 1951. Thanks to these
images, Trujillo told Astronomy, "We know the orbit much better now.
It's quite similar to Pluto's."
The object's distance from the Sun varies between 30.9 AU and 48.1 AU.
One AU, or astronomical unit, equals the Earth's average distance from
the Sun: 93 million miles (150 million km).
The object takes 248 years to complete its orbit and reached its
farthest point from the Sun in 1989. It's now inbound, Trujillo says,
"But don't hold your breath — it won't reach perihelion until 2113."
The team found the object one day short of the 74th anniversary of when
Pluto was discovered, February 18, 1930. That's appropriate because 2004
DW's orbit places it in a class of icy objects sometimes called
"plutinos." These objects occupy Pluto-like orbits in the Kuiper Belt, a
collection of frozen worldlets circling the solar system in a realm
beyond Neptune. Astronomers have cataloged some 800 Kuiper Belt Objects
(KBOs) since 1992.
Until the discovery of 2004 DW, the largest-known KBO was an object
named Quaoar, which was discovered in 2002 by Brown and Trujillo. With
an estimated diameter of 780 miles (1,250 km), Quaoar is larger than
Pluto's moon Charon and has a volume big enough to hold all 50,000 of
the numbered asteroids in the solar system.
Because astronomers know the distance to 2004 DW, its brightness should
indicate its size relative to Quaoar if both objects reflect the same
proportion of sunlight. At the moment, says Trujillo, 2004 DW appears to
be about 870 miles (1,400 km) across, making it the new record holder.
"We'll be attempting to measure that in the next week or two with the
IRAM telescope in Spain," Trujillo adds. This is the same heat-sensitive
telescope Trujillo and Brown previously used to refine estimates of
Quaoar's size. In addition, the team will attempt to obtain images with
the Hubble Space Telescope and, possibly, the Spitzer Space Telescope.
Both Brown and Trujillo believe on the basis of statistical arguments
that a few objects larger than Pluto eventually will be found in the
Kuiper Belt. "Since there are only a few really large ones, you have to
cover a lot of sky to find them," explains Trujillo. "We have a
dedicated program to find objects like this in the outer solar system."
For a few hours each night, the team images the sky with the
170-million-pixel QUEST CCD camera attached to the 48-inch Schmidt
"If Pluto were discovered today, it would be called a Kuiper Belt
Object, not a planet," adds Trujillo. "Scientists have not yet created a
good definition of planet that encompasses the Kuiper Belt."
"It's now only a matter of time before something is going to be
discovered out there that will change our entire view of the outer solar
system," Mike Brown notes.
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