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Location: UFOUpDatesList.Com > 2004 > Mar > Mar 16

Astronomers Discover Mysterious Planet-Like Body

From: UFO UpDates - Toronto <ufoupdates.nul>
Date: Tue, 16 Mar 2004 08:36:54 -0500
Fwd Date: Tue, 16 Mar 2004 08:36:54 -0500
Subject: Astronomers Discover Mysterious Planet-Like Body

Source: NASA Science


Mysterious Sedna

Astronomers have discovered a mysterious planet-like body in the
distant reaches of the solar system.

March 15, 2004: NASA-funded researchers have discovered the most
distant object orbiting the sun. It's a mysterious planet-like
body three times farther from Earth than Pluto.

"The sun appears so small from that distance that you could
completely block it out with the head of a pin," said Dr. Mike
Brown, California Institute of Technology (Caltech), Pasadena,
Calif., associate professor of planetary astronomy and leader of
the research team. The object, called Sedna for the Inuit
goddess of the ocean, is 13 billion kilometers (8 billion miles)
away, in the farthest reaches of the solar system.

Above: An artist's rendition shows the newly discovered planet-
like object, dubbed "Sedna," in relation to other bodies in the
Solar System, including Earth and its Moon, Pluto, and Quaoar.

This is likely the first detection of the long-hypothesized
"Oort cloud," a faraway repository of small icy bodies that
supplies the comets that streak by Earth. Other notable features
of Sedna include its size and reddish color. After Mars, it is
the second reddest object in the solar system. It is estimated
Sedna is approximately three- fourths the size of Pluto. Sedna
is likely the largest object found in the solar system since
Pluto was discovered in 1930.

Brown, along with Drs. Chad Trujillo of the Gemini Observatory,
Hawaii, and David Rabinowitz of Yale University, New Haven,
Conn., found the planet-like object, or planetoid, on Nov. 14,
2003. The researchers used the 48-inch Samuel Oschin Telescope
at Caltech's Palomar Observatory near San Diego. Within days,
telescopes in Chile, Spain, Arizona and Hawaii observed the
object. NASA's new Spitzer Space Telescope also looked for it.

Sedna is extremely far from the sun, in the coldest known region
of our solar system, where temperatures never rise above minus
240 degrees Celsius (minus 400 degrees Fahrenheit). The
planetoid is usually even colder, because it approaches the sun
only briefly during its 10,500- year solar orbit. At its most
distant, Sedna is 130 billion kilometers (84 billion miles) from
the sun, which is 900 times Earth's solar distance.

Scientists used the fact that even the Spitzer telescope was
unable to detect the heat of the extremely distant, cold object
to determine it must be less than 1,700 kilometers (about 1,000
miles) in diameter, which is smaller than Pluto. By combining
available data, Brown estimated Sedna's size at about halfway
between Pluto and Quaoar, a smaller planetoid discovered by the
same team in 2002.

The elliptical orbit of Sedna is unlike anything previously seen
by astronomers. It resembles the orbits of objects predicted to
lie in the hypothetical Oort cloud--a distant reservoir of
comets. But Sedna is 10 times closer than the predicted distance
of the Oort cloud. Brown speculated that this "inner Oort cloud"
might have been formed billions of years ago when a rogue star
passed by the sun, nudging some of the comet-like bodies inward.

Left: Sedna lies farther from the sun than Pluto. Click on the
image to view Sedna's complete orbit.

"The star would have been close enough to be brighter than the
full moon, and it would have been visible in the daytime sky for
20,000 years," Brown explained. Worse, it would have dislodged
comets farther out in the Oort cloud, leading to an intense
comet shower that could have wiped out some or all forms of life
that existed on Earth at the time.

Rabinowitz said there is indirect evidence that Sedna may have a
moon. The researchers hope to check this possibility with NASA's
Hubble Space Telescope. Trujillo has begun to examine the
object's surface with one of the world's largest
optical/infrared telescopes, the 8-meter (26- foot) Frederick C.
Gillett Gemini Telescope on Mauna Kea, Hawaii. "We still don't
understand what is on the surface of this body. It is nothing
like what we would have predicted or what we can explain," he

Right: This is what Sedna looks like through the Palomar
Observatory's 48-inch telescope. The dim object caught the
attention of astronomers because it was moving, slightly, across
the starry field. [More]

Sedna will come closer to Earth in the years ahead, but even at
closest approach, about 72 years from now, Sedna is very far
away--farther than Pluto. Then it will begin its 10,500-year
trip back to the far reaches of the solar system. "The last time
Sedna was this close to the sun, Earth was just coming out of
the last ice age. The next time it comes back, the world might
again be a completely different place," Brown said.

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