## Thursday, August 24, 2006

### Prague defenestration of Pluto

Democracy may be a tough thing. Last week, we reported about the proposal to have 12 planets.

Figure 1: The dwarf planet Pluto and its friends

However, 9000 astronomers who gathered in Prague have just voted differently. The vote was overseen by Jocelyn Bell-Burnell and her teddy bear. It is still true that a planet is an object that is spherical because of its gravity that orbits around the star. However, a new adjective was added.

Which adjective? The asteroid Ceres was promoted to a dwarf planet. Pluto was downgraded to a dwarf planet. Charon, previously known as Pluto's moon, was downgraded from a moon to a "small solar system body". On the other hand, the piece of rock 2003 UB313 was promoted to a dwarf planet, too.

The adjective "dwarf" means that the celestial body is not large enough to clear its orbit from other objects.

There are some good news for Charon: Pluto and Charon can also be called a double planet. This new equality is no reason for feminists to celebrate because both Pluto and Charon are male. On the other hand, feminists have succeeded in adding another female member among the planets so that Venus doesn't feel so lonely and discriminated: the dwarf planet 2003 UB313 will be promoted to a woman called Xena.

Figure 2: Xena, a new dwarf planet. She is actually larger than Pluto. Her moon is informally called Gabrielle. To make things more complicated, Gabrielle's sister in the movie was Lila, and Lila is also an alternate nickname for the dwarf planet Xena herself, chosen after a newborn daughter (Lilah) of one of the discoverers Michael E. Brown. ;-)

This humiliating experience that has affected Pluto's life may be viewed as the fourth defenestration of Prague, after the events in 1419, 1618, and 1948. Congratulations to Ceres, Charon, and 2003 UB313. Once again, the main reason of Pluto's bad luck is not its size or the crappy stuff that it is made of; instead, it is the fact that its path is perturbed by the Neptune. In other words, Pluto has not yet cleared its orbit.

NASA has sent a \$700 million spacecraft to Pluto and argues that it won't discriminate against Pluto just because it is size-challenged. According to the new convention, there are eight dwarf planets in the solar system.