Pluto's status attacked - Washington Post

Pluto might not be called a planet any more. These are only the current media speculations around the International Astronomers Union meetings taking place in Prague this week.

Some arguments are given below to support this controversial decision.
However, a compromise may also be reached by calling Pluto and other Kuiper Belt Objects "dwarf planets". There already are two groups of planets: The gas planets and the rocky planets. A third group may be created for a dozen of Kuiper Belt objects. That would mean that the solar system would have 14 more planets in addition to the 9 "historical planets".

Here are some 2 good reasons why Pluto should still be called a planet:


1> Size: The next smallest planet of the solar system is Mercury. Mercury is nearly 6,000 times less massive that the biggest planet Jupiter. In comparison, Pluto is less than 30 times less massive than Mercury. Why should we say that Pluto is too small to be called a planet then?

2> Roundness: Pluto is massive enough (by far) to be round-shaped like any other planets. All objects bigger than 500 km in diameter are round-shaped. Pluto's diameter is 2,274 km.

It's worth mentioning that, historically, a planet is defined as an object with a "stable" orbit around the sun. From that perspective, Pluto is not that much a planet given that its orbit is irregular. However, we are living in the age of space exploration and we can actually see what the planets look like. Given what we know about all the other planets, there are no good reasons to consider Pluto's status from the perspective of its orbit only.

3> Given the high discovery rate of new "Kuiper Belt Objects", we may expect to be introduced to a very big one... bigger than Mercury. Then what?

4> If you feel alienated by the term "Kuiper Belt Objects", you're not the only one. Calling all these objects "planets" will give them the fame and the prestige that they deserve.

5> The real reason for demoting Pluto's status is this one: Too many planets in the solar system! Should we start lamenting on the diversity of the universe?

Sailom


http://www.washingtonpost.com/wp-dyn/content/article/2006/08/13/AR2006081300286.html

Pluto's status attacked

By Alan Crosby

Reuters
Sunday, August 13, 2006; 12:55 PM

PRAGUE (Reuters) - Despite being the farthest planet from Earth in our solar system, Pluto has come under attack from astronomers and may be about to lose its status in the battle.

Some 3,000 astronomers and scientists from around the world will meet in Prague this week to decide whether Pluto, discovered in 1930, measures up to the definition of a planet.

In defining for the first time what exactly a planet is, the International Astronomers Union (IAU) may be forced to downgrade Pluto's status, or add as many as 14 others.

Such a decision would send shockwaves through the scientific community, instantly outdate textbooks, and cause educators to re-teach the basics of our solar system.

"The pivotal question is the status of Pluto, which is clearly very different from Jupiter, Saturn, Uranus, and Neptune," Owen Gingerich, professor of Astronomy and History of Science emeritus a the Harvard-Smithsonian Center for Astrophysics told Reuters.

Debate has raged within the scientific community over the status of Pluto for decades after the planet was found to be only one four-hundredths of the mass of the earth.

That discussion intensified in 2003 when astronomers at the California Institute of Technology discovered UB 313. Nicknamed Xena after the character in the television show, UB 313 is one of more than a dozen celestial bodies in our solar system found to be larger than Pluto.

Xena and Pluto are large icy bodies that reside in the Kuiper Belt -- where thousands of floating bodies travel -- beyond Neptune. Images from the Hubble Space Telescope put Xena's diameter at 1,490 miles or so. That is slightly bigger than Pluto, which measures 1,422 miles across.

Gingerich is the chair of a committee that was asked to come up with a definition of a planet and hand it to the IAU general assembly, which runs August 14-25.

In the run-up to the assembly, emotions have been running high in both directions.

Some have appealed to Gingerich's group not to downgrade Pluto, saying it would disappoint children and throw our understanding of the universe into chaos.

Others say let the chips fall where they may and seem to relish the idea of overturning our current view of the universe.

Gingerich said that modern technologies have allowed scientists to delve into the solar system further, and in more detail, than ever before. Therefore, it is no surprise that questions on the fundamental assumptions of it are arising.

"Should it (Pluto), for historical reasons, be considered a planet like the rest?" Gingerich asks, refusing to tip his hand on how the seven-member group has agreed after deciding on the wording in June.

Scientists say the group may make a new class of planets that accepts large bodies such as Xena and Pluto that do not measure up to the eight larger planets. They could also drop Pluto's status as a planet or expand the list of planets to include many similarly-sized bodies found in the solar system.