Saturday, July 22, 2006

SEDNA: The First New Find


Here are two earlier news releases about Sedna:

WASHINGTON (Reuters) - A newly discovered dark and frigid world, a bit smaller than Pluto and three times farther away, has emerged as the most distant object in the solar system, astronomers said on Monday.

The new "planetoid," named Sedna after an Inuit goddess who created the sea creatures of the Arctic, is by far the coldest and most distant object known to orbit the sun, a team of researchers announced.

At more than 8 billion miles from the sun, the temperature on Sedna never gets above minus 400 degrees Fahrenheit.

"The sun appears so small from that distance that you could completely block it out with the head of a pin," said Mike Brown, an astronomer at California Institute of Technology, who led the research team.

First detected on Nov. 14 with the Samuel Oschin Telescope near San Diego, California, Sedna was observed within days on telescopes from Chile to Spain, Arizona and Hawaii.

NASA's new orbiting Spitzer Space Telescope, which looks at the universe with infrared detectors that peer through cosmic dust, was also trained on the distant object.

The Spitzer scope found that Sedna probably has about three-fourths the diameter of Pluto, which would make it the biggest object found in the solar system since Pluto's discovery in 1930.

Astronomers to Detail Aspects of Sedna
Mon Mar 15, 9:37 AM ET Add Science - AP to My Yahoo!

By ANDREW BRIDGES, AP Science Writer

LOS ANGELES - It is a frozen world more than 8 billion miles from Earth and believed to be the farthest known object within our solar system.

NASA planned a Monday press conference to offer more details about Sedna, a planetoid between 800 miles and 1,100 miles in diameter, or about three-quarters the size of Pluto.

Named for the Inuit goddess who created the sea creatures of the Arctic, Sedna lies more than three times farther from the sun than Pluto. It was discovered in November.

"The sun appears so small from that distance that you could completely block it out with the head of a pin," said Mike Brown, an astronomer at the California Institute of Technology who led the NASA-funded team that found Sedna.

That makes Sedna the largest object found orbiting the sun since the discovery of Pluto, the ninth planet, in 1930. It trumps in size another world, called Quaoar, discovered by the same team in 2002.

Brown and his colleagues estimate the temperature on Sedna never rises above 400 degrees below zero Fahrenheit, making it the coldest known body in the solar system.

Sedna follows a highly elliptical path around the sun, a circuit that it takes 10,500 years to complete. Its orbit loops out as far as 84 billion miles from the sun, or 900 times the distance between the Earth and our star.

Brown and Chad Trujillo, of the Gemini Observatory in Hawaii, and David Rabinowitz, of Yale University, discovered Sedna on Nov. 14, 2003, using a 48-inch telescope at Caltech's Palomar Observatory east of San Diego.

Within days, other astronomers around the world trained their telescopes, including the recently launched Spitzer Space Telescope, on the object.

The team also have indirect evidence a tiny moon may trail Sedna, which is redder than all other known solar system bodies except Mars.

Here is a recent news release about Xena:

Scientists Discover 10th Planet's Moon
By ALICIA CHANG, AP Science Writer October 1, 2005
The astronomers who claim to have discovered the 10th planet in the solar system have another intriguing announcement: It has a moon.
While observing the new, so-called planet from Hawaii last month, a team of astronomers led by Michael Brown of the California Institute of Technology spotted a faint object trailing next to it. Because it was moving, astronomers ruled it was a moon and not a background star, which is stationary.
The moon discovery is important because it can help scientists determine the new planet's mass. In July, Brown announced the discovery of an icy, rocky object larger than Pluto in the Kuiper Belt, a disc of icy bodies beyond Neptune. Brown labeled the object a planet and nicknamed it Xena after the lead character in the former TV series "Xena: Warrior Princess." The moon was nicknamed Gabrielle, after Xena's faithful traveling sidekick.
By determining the moon's distance and orbit around Xena, scientists can calculate how heavy Xena is. For example, the faster a moon goes around a planet, the more massive a planet is.
But the discovery of the moon is not likely to quell debate about what exactly makes a planet. The problem is there is no official definition for a planet and setting standards like size limits potentially invites other objects to take the "planet" label.
Possessing a moon is not a criteria of planethood since Mercury and Venus are moonless planets. Brown said he expected to find a moon orbiting Xena because many Kuiper Belt objects are paired with moons.
The newly discovered moon is about 155 miles wide and 60 times fainter than Xena, the farthest-known object in the solar system. It is currently 9 billion miles away from the sun, or about three times Pluto's current distance from the sun.
Scientists believe Xena's moon was formed when Kuiper Belt objects collided with one another. The Earth's moon formed in a similar way when Earth crashed into an object the size of Mars.
The moon was first spotted by a 10-meter telescope at the W.M. Keck Observatory in Hawaii on Sept. 10. Scientists expect to learn more about the moon's composition during further observations with the Hubble Space Telescope in November.
Brown planned to submit a paper describing the moon discovery to the Astrophysical Journal next week. The International Astronomical Union, a group of scientists responsible for naming planets, is deciding on formal names for Xena and Gabrielle.

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