Kuiper Belt

Astronomers from the University of Hawaii and UC Berkeley have discovered the solar system's most distant detected object, which appears to be a small, icy planetoid and could be one of millions forming a comet nursery near Pluto. The body, temporarily named 1992 QB-1, is about 100 miles across, roughly 20% the size of Pluto. It is reddish, suggesting a surface rich in carbon compounds.

Re "Plutonic Love Fades," editorial, Oct. 12: In order to decide whether Pluto and the recently discovered Quaoar should be called planets, it is helpful, amusingly enough, to follow the approach of the father in the movie "My Big Fat Greek Wedding" who was always coming up with Greek etymologies for words. The term "planet" comes from the Greek word meaning wanderer, which was used in order to distinguish the then-known planets, which looked like stars, from the stars themselves, which seemed to be fixed in the heavens.

NASA's newest mapping mission, designed to sniff out the dimmest residents of our neighborhood in space, launched successfully this morning from Vandenberg Air Force Base in California. The Delta II rocket carrying the Wide-Field Infrared Survey Explorer spacecraft lifted off at 6:09 a.m., Pacific time. About eight minutes later, the 1,485-pound WISE craft entered space. About 52 minutes into the flight, the craft's second-stage rocket ignited again, placing the vehicle into its assigned polar orbit 326 miles above the Earth.

Pluto has three moons, not one, new images from the Hubble Space Telescope suggest. Pluto, discovered as the ninth planet in 1930, was thought to be alone until its moon Charon was spotted in 1978. The new moons, more than twice as far away as Charon and only a fraction as bright, were spotted by Hubble in May. Although the observations have to be confirmed, members of the team that discovered the satellites said Monday that they felt confident about their data.

Astronomers said Thursday they have found a frozen object 4.4 billion miles from Earth that appears to be more than half the size of Pluto and larger than the planet's moon. If confirmed, the so-called planetoid would become the largest object found in our solar system since the ninth planet was first spied in 1930. Preliminary observations suggest the frozen celestial body is 10% larger than Quaoar, an 800-mile-diameter object found in 2002.

Astronomer Clyde Tombaugh could not have known how fitting it was to call his new planet Pluto, after the Roman god of the underworld. In the 76 years since Tombaugh discovered the solar system's ninth planet, Pluto has remained an enigma -- a shrouded phantom lurking in the dark recesses of the solar system. Three billion miles from Earth, the diminutive ice world is so distant that even the Hubble Space Telescope can produce only a hazy image of an object resembling a chewed-on tennis ball.

Astronomers have discovered what they believe is the 10th and most distant planet in our solar system: a ball of rock that is 1 1/2 times as big as Pluto and about three times as far out. While there are still no precise measurements of the new object, an analysis of its brightness and distance suggests that its diameter is up to 2,000 miles. "We are 100% confident that this is the first object bigger than Pluto ever found in the outer solar system," said Caltech astronomer Michael A.

Clyde Tombaugh might have missed it had he been a little less attentive as he stared through an eyepiece while switching back and forth between photographic images of the night sky. A recurring speck on two successive images that also contained perhaps another 300,000 dots -- pinprick-sized images of stars and other space objects -- was all the evidence there was that Tombaugh was onto something extraordinary. But it was enough.

Saturn's rings may be vintage jewelry as old as the solar system, and they're practically sparkling with water ice, according to data from NASA's Cassini spacecraft. The findings, released this week in the Astrophysical Journal, give planetary scientists a window into the solar system's birth and development, and show that the formation of at least one of the planet's 62 known moons may have been a little more complicated than thought. Launched in 1997, the Cassini mission spacecraft is now on its third lifetime exploring Saturn's complex system and still turning up remarkable new information about the ringed gas giant.

Venezuelan astronomers led by physicist Ignacio Ferrin have named a Kuiper Belt object on the fringes of the solar system after Huya, the rain god in Venezuela's indigenous Wayuu culture. The frozen clump of rock, known as 2000 EB173, was discovered in March 2000 in the Kuiper Belt, a ring of icy debris that orbits the sun beyond Neptune. It takes 256 years to make one revolution. Under guidelines set by the International Astronomical Union, such an object must be named after a mythological