The weekly newsletter for Fed2 by ibgames

EARTHDATE: August 20, 2006

Official News - page 8

REAL LIFE NEWS: SOLAR SYSTEM EXPANSION

Ever since the discovery of new planet-sized bodies out in the far reaches of the Solar System, debate has been raging in astronomical circles about whether these lumps of rocks can be called planets or not. If not, then it means Pluto - which is smaller than some of the new discoveries and up to now has been considered to be the ninth planet in our system - isn't really a planet either. If they are planets, it means including bodies such as Ceres, which up to now has been counted as an asteroid.

Now a new compromise proposal has been put forward which mostly satisfies everyone, and it will be voted on next week at a get-together of the International Astronomers Union in Prague.

The new definition of a planet would be:

"A planet is a celestial body that (a) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (b) is in orbit around a star, and is neither a star nor a satellite of a planet."

The definition also sets out a class structure for different kinds of planets, to distinguish between the inner planets and distant bodies in less circular orbits. Thus, anything with an orbit longer than 200 years would be classed as a "pluton". This class will include one of the new bodies discovered in 2003, popularly known as Xena. Charon, which until now was considered a moon of Pluto, will also be upgraded because its behavior makes it a companion planet to Pluto rather than a subsidiary satellite body. Kind of a plutonic relationship, perhaps?

Ceres, which is the largest known asteroid at around 580 miles in diameter, also gets the upgrade to planet status. There are twelve other candidate planets on the IAU's watch list which could be accorded official status in the future.


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