Friday, August 25, 2006

Classicals, Dwarfs, and Trans-Neptunians

Hooookay...the International Astronomical Union (IAU) just released the new definition of "planets" and a new category, "dwarf planets."

(1) A "planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighbourhood around its orbit.

(2) A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.

As an add-on, Wikipedia defines trans-Neptunian objects as objects in the solar system that orbit the sun at a greater distance on average than Neptune. This has three divisions--the Kuiper belt, Scattered disk, and Oort cloud.

There are now eight classical planets-- everyone except Pluto.

Pluto is now a dwarf planet, and part of a new category of Trans-Neptunian objects accoring to the IAU. New objects will be added to this new category, with Pluto as the prototype.

Charon is also now a dwarf planet. It used to be known as Pluto's moon, but I guess it isn't anymore since dwarf planets exclude satellites.

Ceres, formerly an asteroid, is now a dwarf planet.

Xena, whose name might change, is now a dwarf planet.

Whew! And to think that original proposals went as far as 12 planets, even more. Buti naman at isang planeta lang ang ipinagbago. Mas matipid sa mga teksbuks--tapal action with White-Out.

5 comments:

Jac said...

hahaha! ayus sa closing a ;)

Carver said...

hee hee hee

juOn said...

Seriously the repercussion of the IAU resolution is mind-boggling. It will cause ripples not just in science but also in history and culture. And you wouldn't believe how emotional some people can get about the issue---comparable only to a parent discovering that a child he cared for is not his own.

Anonymous said...

paano na si sailor pluto?

decorator said...

kawawang mga gradeschoolers...

hay naku, dami na namang mememorizin....

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