Horizon 9pm Tonight

[Kain]

I have a problem with some of the so called "moons"

Take Phobos, 22km in diameter that is a "moon" of Mars. If you put Phobos into orbit around the Sun, what would it be classified as? An asteroid

Take Titan, 5150km in diameter and send that into orbit around the Sun, what would it be classified as? A planet

Thats a bit of a difference.

The reality is Phobos and indeed Deimos, the other "moon" of Mars are in reality captured asteroids.

While I do agree with what your saying, but with respect, Deimos and Phobos are in orbit around Mars, so they are satellites of that planet, asteroid or not. You can same for some of the moons around of the gas giants, not all of them are worlds of size.

For Pluto, leave it at it is, it's been a planet for 76 years, alot of people have been taught that it's a planet.

Anything bigger than Pluto (Xena??) should be declared a planet, make Jupiter a baseline.

Ganymede and Titan could be classed as planets too, after all, I read somewhere if Jupiter did something with hydrogen it would become a small star.. Plant's orbiting planets..not that far out is it really.

Kain

[Methuselah]

Can't we just leave things as they are? It's only about names, anyway?

PS: Not that Pluto's going to give a sh*t!

Edited June 24, 2006 by Pete Tattum

[geri2k]

It's a small world!

[crimsone]

OK, I think I shall have an attempt at this...

Asteroid - Any solid object in orbit around the sun that is either part of a "belt" of such objects, or is of a composition that indicates that it has been knocked out of such a "belt", but has not aquired any properties that would indicate a definition as a comet. Further, an asteroid cannot be in a stable orbit of any "planet".

Comet - that's pretty well defined already!

Moon - and natural object in a stable orbit of a planet (any natural sattelite of a planet - including previously captured asteroids), where the planet is it's main steering influence, above a given size, to be defined either in terms of the size of the planet, or in terms of a set size, to be decided later. It should be a free-standing sattelite in that it must have an individual orbit apart from other satellites.

Planet - Any natural body in a stable orbit around a solar systems central star (stars), where the main steering force/gravitational pull is the star itself, above a certain size (as with moons), and is free-standing (not part of a belt of such objects), with an orbit independant of such other objects

(free-standing requires definition, but I'm sure it's obvious what I mean. Obviously other planets effect the orbit of a given planet or vice versa. Jupiter, for example, being the giant vacuum cleaner of the solar system.)

[Weather-history]

The Sunday Times has said that Xena is expected to be announced as the 10th planet next month

http://www.timesonline.co.uk/article/0,,2087-2281816,00.html

Edited July 23, 2006 by Mr_Data

[stella]

The Sunday Times has said that Xena is expected to be announced as the 10th planet next month

That should be 2003 UB313.