RIP to Pluto

Leading astronomers on Thursday approved historic new guidelines under which distant Pluto is no longer defined as a planet.

After a tumultuous week of clashing over
the essence of the cosmos, the International Asronomical Union stripped
Pluto of the planetary status it has held since its discovery in 1930.

It is the first time that scientists have had a formal definition of what is - and is not - a planet.

Thursday’s decision by the prestigious
international group spells out the basic tests that celestial objects
will have to meet before they can be considered for admission to the
elite cosmic club.

For now, membership will be restricted to
the eight “classical” planets in the solar system: Mercury, Venus,
Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

Much-maligned Pluto doesn’t make the grade
under the new rules for 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.”

Pluto is automatically disqualified because its oblong orbit overlaps with Neptune’s.

Instead, it will be reclassed in a new category of “dwarf planets,” similar to what have long been termed “minor planets.”

The definition also lays out a third class
of lesser objects that orbit the sun - “small solar system bodies,” a
term that will apply to numerous asteroids, comets and other natural
satellites.


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August 24, 2006 | Filed Under General World | 3 Comments 

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