Wednesday, August 16, 2006

New research shows 12 planets in Solar System

The world's astronomers and the International Astronomical Union have concluded two years of research that shows there may be 12 planets in our solar system. The work defined the difference between planets and the smaller solar system bodies, such as comets and astroids. If the definition is approved by the astronomers who gather at the IAU General Assembly in Prague this month, the solar system will include 12 planets, with more to come, according to the IAU.

The 12 recognised planets are: Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto, Charon and 2003 UB313 (provisional name). There are eight "classical planets": Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. Ceres is a planet, but because it is smaller than Mercury, one may describe it as a "dwarf planet". A new category of planet is now defined: "plutons". Pluto (the prototype for this classification), Charon, and 2003 UB313 fall into the growing category of planets called "plutons".


simon said...

Fricking lies I tell ya lies. There are 8 planets. There others are wannabe planets. But it does pose an interesting question what is a planet what defining caracteristic does it have. This whole thing of size is a bit random. You could try atmosphere. But some moons have atmosperes yet Mercury does not due to proximity to the sun.

sciencegeek said...

Believe it or not, the current definition for what makes a planet is based on thermonuclear fusion in a star. This is thirteen jupiter masses - so anything above this mass is a star. This doesn't differentiate between planets and asteroids etc. It just gives an upper limit to how massive a planet can be.

There's a big push for formation mechanism to be the defining characteristic of planets (ie formed in a protoplanetary disk) but that still doesn't give a specification as to what's a planet, and what's a by-product of the disk. The IAU's definition in question is based on shape, more than size. It's proposing to define planets by their near-circular shape.