9 or 12 Planets?

#1

Plan would add planets to solar system

By WILLIAM J. KOLE, Associated Press Writer

PRAGUE, Czech Republic - The universe really is expanding †™‚¢‚¢¢¢¬…¡‚¬‚¢¢¢‚¬Å¡‚¬‚

astronomers are proposing to rewrite the textbooks to say that our solar system has 12 planets rather than the nine memorized by generations of schoolchildren.

Much-maligned Pluto would remain a planet †™‚¢‚¢¢¢¬…¡‚¬‚¢¢¢‚¬Å¡‚¬‚

and its largest moon plus two other heavenly bodies would join Earth's neighborhood †™‚¢‚¢¢¢¬…¡‚¬‚¢¢¢‚¬Å¡‚¬‚

under a draft resolution to be formally presented Wednesday to the International Astronomical Union, the arbiter of what is and isn't a planet.

"Yes, Virginia, Pluto is a planet," quipped Richard Binzel, a professor of planetary science at the Massachusetts Institute of Technology.

The proposal could change, however: Binzel and the other nearly 2,500 astronomers from 75 nations meeting in Prague to hammer out a universal definition of a planet will hold two brainstorming sessions before they vote on the resolution next week. But the draft comes from the IAU's executive committee, which only submits recommendations likely to get two-thirds approval from the group.

Besides reaffirming the status of puny Pluto †™‚¢‚¢¢¢¬…¡‚¬‚¢¢¢‚¬Å¡‚¬‚

whose detractors insist it shouldn't be a planet at all †™‚¢‚¢¢¢¬…¡‚¬‚¢¢¢‚¬Å¡‚¬‚

the new lineup would include 2003 UB313, the farthest-known object in the solar system and nicknamed Xena; Pluto's largest moon, Charon; and the asteroid Ceres, which was a planet in the 1800s before it got demoted.

The panel also proposed a new category of planets called "plutons," referring to Pluto-like objects that reside in the Kuiper Belt, a mysterious, disc-shaped zone beyond Neptune containing thousands of comets and planetary objects. Pluto itself and two of the potential newcomers †™‚¢‚¢¢¢¬…¡‚¬‚¢¢¢‚¬Å¡‚¬‚

Charon and 2003 UB313 †™‚¢‚¢¢¢¬…¡‚¬‚¢¢¢‚¬Å¡‚¬‚

would be plutons.

Astronomers also were being asked to get rid of the term "minor planets," which long has been used to collectively describe asteroids, comets and other non-planetary objects. Instead, those would become collectively known as "small solar system bodies."

If the resolution is approved, the 12 planets in our solar system listed in order of their proximity to the sun would be Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto, Charon, and the provisionally named 2003 UB313. Its discoverer, Michael Brown of the California Institute of Technology, nicknamed it Xena after the warrior princess of TV fame, but it likely would be rechristened something else later, the panel said.

The galactic shift would force publishers to update encyclopedias and school textbooks, and elementary school teachers to rejigger the planet mobiles hanging from classroom ceilings. Far outside the realm of science, astrologers accustomed to making predictions based on the classic nine might have to tweak their formulas.

Even if the list of planets is officially lengthened when astronomers vote on Aug. 24, it's not likely to stay that way for long: The IAU has a "watchlist" of at least a dozen other potential candidates that could become planets once more is known about their sizes and orbits.

"The solar system is a middle-aged star, and like all middle-aged things, its waistline is expanding," said Jack Horkheimer, director of the Miami Space Transit Planetarium in the United States and host of Public Broadcasting's Stargazer television show.

Opponents of Pluto, which was named a planet in 1930, still might spoil for a fight. Earth's moon is larger; so is 2003 UB313 (Xena), about 70 miles wider.

But the IAU said Pluto meets its proposed new definition of a planet: any round object larger than 800 kilometers (nearly 500 miles) in diameter that orbits the sun and has a mass roughly one-12,000th that of Earth. Moons and asteroids will make the grade if they meet those basic tests.

Roundness is key, experts said, because it indicates an object has enough self-gravity to pull itself into a spherical shape. Yet Earth's moon wouldn't qualify because the two bodies' common center of gravity lies below the surface of the Earth.

"People were probably wondering: If they take away Pluto, is Rhode Island next?" Binzel quipped. "There are as many opinions about Pluto as there are astronomers. But Pluto has gravity on its side. By the physics of our proposed definition, Pluto makes it by a long shot."

IAU President Ronald D. Ekers said the draft definition, two years in the making, was an attempt to reach a cosmic consensus and end decades of quarreling. "We don't want an American version, a European version and a Japanese version" of what constitutes a planet, he said.

Neil deGrasse Tyson, director of the Hayden Planetarium at New York's American Museum of Natural History †™‚¢‚¢¢¢¬…¡‚¬‚¢¢¢‚¬Å¡‚¬‚

miscast as a "Pluto-hater," he contends, merely because Pluto was excluded from a solar system exhibit †™‚¢‚¢¢¢¬…¡‚¬‚¢¢¢‚¬Å¡‚¬‚

said the new guidelines would clear up the fuzzier aspects of the Milky Way.

"For the first time since ancient Greece, we have an unambiguous definition," he said. "Now, when an object is debated as a possible planet, the answer can be swift and clear."

___

AP Science Writers Alicia Chang in Los Angeles and Seth Borenstein in Washington contributed to this story.

___

On the Net:

International Astronomical Union, http://www.iau.org

#2

If our moon is larger than Pluto, how come our moon wouldn't be a planet, and if that's the case, I'm sure that Jupiter has some big ass moons, some that may even rival earth in size...Under the new rule, they too would be planets..?

#3

It doesn't have to do with size, it has to do with their orbit. The moon is not rotating around the sun, it's rotating around Earth. Pluto has a wierd orbit, but it's still around the sun.

#4

QUOTE(trashtalkr)It doesn't have to do with size, it has to do with their orbit. The moon is not rotating around the sun, it's rotating around Earth. Pluto has a wierd orbit, but it's still around the sun.
While I understand that, the following line makes it confusing:
QUOTE(Mr. SM)Plan would add planets to solar system
Besides reaffirming the status of puny Pluto †™‚¢‚¢¢¢¬…¡‚¬‚¢¢¢‚¬Å¡‚¬‚

whose detractors insist it shouldn't be a planet at all †™‚¢‚¢¢¢¬…¡‚¬‚¢¢¢‚¬Å¡‚¬‚

the new lineup would include 2003 UB313, the farthest-known object in the solar system and nicknamed Xena; Pluto's largest moon, Charon; and the asteroid Ceres, which was a planet in the 1800s before it got demoted.
Have they determined that Charon does not actually orbit pluto? If Pluto's moon Charon orbits Pluto, but is deemed a planet, then almost every other moon we know of must be deemed a planet as well. Wounldn't you agree?

#5

QUOTE(http://hometown.aol.com/bobalien99/plutocha.htm)Pluto's moon, Charon, was discovered in 1978. It is quite a big moon compared with the size of the planet it orbits, with a width (diameter) of about 1,212 kilometres. This compares with the width of Pluto which is 2,280 kilometres. The moon is only 19,640 kilometres away from the planet. Only Mars has a moon which orbits the planet so closely (Phobos at 9,270 kilometres). Earth's moon orbits Earth at a distance of 384,400. It takes just over only 6 days for Charon to orbit Pluto. It is believed that Pluto and Charon are made of the same material, although this will not be discovered for certain until the Pluto Express mission arrives in 2012 to discover more information about the two objects.
Just a little info.

#6

Size Matters (in spite of what my wife tells me, I know this to be true) .... but it's not the only thing (so I keep clinging to hope... /smile.gif" style="vertical-align:middle" emoid=":)" border="0" alt="smile.gif" />). Our moon's primary rotation is around the Earth which makes them a system. The Gravitational Center of this system lies within the boundry of the earth's crust. The Gravitational Center of the system concept is also one of the proposed criteria to determine a "planet". Because the gravitational center of the Pluto / Charon system lies outside of either object, it could be viewed as a binary planet system where both "planets" are caught in each other's gravitational tug while circling the sun. Binary systems (of stars, specifically) are not unheard of in our universe.

Hope that helps...

#7

All of this goes to show is that what we commonly refer to as "gravity" is in fact something else...

Bot · #8

Pluto gets the boot

The debate is over, Pluto was canned. The new definition of a planet...

"a celestial body that is in orbit around the sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a ... nearly round shape, and has cleared the neighborhood around its orbit."

Seems to make sense to me...

#9

We should only define a rock/gas anomoly as a planet if we can ACTUALLY get to it to determine it's proper classification.

#10

hey I completely agree with kramer here.

make note, sound the horns and have it shouted from the rooftops.

ADN

9 or 12 Planets?

9 or 12 Planets?

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