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Pluto's Not So Alone Out There, It Appears

Astronomy: The distant, icy sphere dubbed Quaoar is said to be too small to be a planet, although it is planet-like.


Two Caltech astronomers using an aging telescope to scan the fringes of the solar system have found an object half the size of Pluto--a distant, icy sphere they have dubbed Quaoar.

The scientists say the dark, reddish object is the largest body discovered in the solar system since Pluto was spotted in 1930. Although precise measurements are impossible to make from Earth, Quaoar (pronounced KWA-wahr) is estimated to be about 780 miles across, the size of Pluto's moon, Charon. It dances near the edge of the solar system 1 billion miles beyond Pluto, 4 billion miles from Earth.

The find by Mike Brown and Chad Trujillo, two Caltech astronomers who have worked in relative obscurity to survey the outer reaches of the solar system, was announced Monday at a meeting of planetary scientists in Birmingham, Ala.

Quaoar joins a handful of other strange, large objects recently found in Pluto's neighborhood, the Kuiper Belt, a swath of icy cosmic residue that extends from Neptune to the solar system's outer limits.

For The Record
Los Angeles Times Wednesday October 09, 2002 Home Edition Main News Part A Page 2 ..CF: Y 5 inches; 196 words Type of Material: Correction
Quaoar--A story in Tuesday's Section A stated that the newly discovered solar system object Quaoar takes days to circle the sun. It should have read 288 years.
For The Record
Los Angeles Times Friday October 11, 2002 Home Edition Main News Part A Page 2 National Desk 5 inches; 197 words Type of Material: Correction
Quaoar location--A graphic in Section A Tuesday on a distant, icy sphere dubbed Quaoar mislabeled the distance between the sphere and Pluto. The correct distance is 1 billion miles.

Its discoverers say Quaoar is too small to be a planet, although they note it is quite planet-like in its behavior and acts far more like a planet than Pluto--the smallest planet in the solar system, with a diameter of 1,400 miles. That finding immediately revived a simmering debate among astronomers about whether Pluto should be stripped of its designation as a planet, and is forcing astronomers to reconsider even basic notions about the solar system as a whole.

"There's a whole zoo of things out there that we ought to be exploring but haven't even been able to fit into our conceptual framework," said David Jewitt, an astronomer at the University of Hawaii who with Jane Luu discovered the first object in the Kuiper Belt in 1992.

Other Plutonian peers found in recent years include Varuna, a 550-mile-across object named for the Vedic god of the oceans; Ixion, an object estimated to be nearly as large as Quaoar, named for the mythical Greek king who fathered the Centaurs; and Rhadamanthus, a smaller object named for one of three judges of the underworld in Greek mythology.

Quaoar takes its name from the creation myth of the original inhabitants of the Los Angeles Basin, the Tongva Indian tribe, also known as the Gabrielenos. According to tribal elder Mark Acuna, Quaoar is the formless, genderless creation force that sang into existence the other deities--Sky Father, Earth Mother and Grandfather Sun.

In this age of eagle-eyed space telescopes that can locate some of the most distant objects in our universe, the discovery of these startlingly large objects so close to home is something of a wake-up call. Even veteran astronomers are calling it "awesome," "spectacular" and "cool."

Quaoar orbits in a region of space so cold and dark that our blindingly bright sun appears there only as another star in the night sky. Until recently, most astronomers thought the region was a boring stretch of emptiness containing only Pluto, its moon and a long-sought entity called Planet X, whose theorized existence eventually was disproved.


Billions of Objects

"People didn't study [the area] because they didn't know anything was there," Jewitt said.

Astronomers since have realized that the Kuiper Belt is swarming with unexpected objects. In the 10 years since Jewitt's discovery, scientists have found about 600 Kuiper Belt objects, or KBOs. Models suggest that there could be 10 billion of the objects there. Depending on the vagaries of their orbits and the linguistic predilections of astronomers, they are called "plutinos," "trans-Neptunian objects," "scattered objects" and "cubewanos" for the first KBO, a 175-mile-diameter object officially cataloged as QB1 despite Jewitt's proposed name of "Smiley."

The objects are a motley collection that defy stereotype. Some objects have such distant, looping orbits that they remain invisible from Earth for hundreds, if not thousands, of years. Except for Pluto with its reflective ice surface, the objects found so far are all dark, their carbon-rich surfaces scorched by a constant bombardment of cosmic rays. Some give off a faint, reddish glow. At least seven waltz with satellites nearly their own size. None appear to have atmospheres. And as large as Quaoar is, scientists expect it will soon be surpassed.

"I think this is spectacular," said Alan Stern, an astronomer at the Southwest Research Institute who leads the Pluto-Kuiper Express, a NASA mission proposed to start journeying toward the Kuiper Belt in 2006. "But I would not be surprised if we found objects substantially larger than Pluto--the size of Mars or even Earth."

None of this bodes very well for Pluto's status as a planet.

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