Is it a little horse or is it a pony?
Thu
31
Aug '06
So the International Astronomical Union have decided that PLUTO is no longer a planet and EARTH is now the 3rd of 8 planets instead of 9, perhaps they should also look at MERCURY:
- pluto has an atmosphere, mercury does not
- pluto has a moon, mercury does not
- is mercury a low orbit asteroid?
I have always thought:
- a satellite is a celestial body orbiting a star or planet
- a star radiates energy by burning its own mass
- a planet is held together in an overall round shape by its own gravitational field (may be solid or not - otherwise we lose the gas giants)
- a moon is satellite to a planet
- a planet is satellite to a star
- an asteroid is satellite to a star and consists of rock or metal
- a comet is satellite to a star and is a frozen mass emitting a ‘tail’ of material away from the star
Astrologers describe a planet as ‘a moving space object’, thats pretty much everything then…
Children can figure it out Try it yourself, ask them to draw:
- a star - pointed object (radiating light or gas)
- a planet - round object (symetrical gravitational field)
- an asteriod - odd shaped lump, most likely triangular (inert & lifeless)
- a comet - as asteriod but with a tail
How come they can manage it and we can’t?
For those that don’t already know, radiating out from our star (the sun) we have:
- 1 Mercury
- 2 Venus
- 3 Earth
- 4 Mars
- (asteriod belt)
- 5 Jupiter
- 6 Saturn
- 7 Uranus
- 8 Neptune
- (Kuiper belt - containing icy masses & Pluto)
At one time Vesta, Ceres, Juno & Pallas were considered planets, but were demoted to asteriods when their orbit and size was determined