How many planets?

[Tigger]

Agafaster wrote:

I reckon on the Earth and Moon being a double planet - ok, it fails the barycentre test, but my opinion is based on the sheer size of our moon, and relative to the earth too. no where else has a moon this big in relation to the primary body.

Charon (Pluto's moon) is significantly bigger in proportion to Pluto.  
    -Tig

[Tigger]

Dandy wrote:

cecilia wrote:
...
Pluto is now a "dwarf planet"

But isn't a "dwarf planet" still a planet?
So I'd say we now have 12 planets, with three of them beeing "dwarf planets"...
 :-?  :-?  :-?

Actually we have four dwarf planets, though that number will grow significantly in the future.  At present we have Ceres, Pluto, Charon and Xena, though Xena is not the actual name for the 4th dwarf planet, just a nickname, its actual name will be picked from a list submitted by its submitter next year sometime.
     -Tig

[Tigger]

Hyperspeed wrote:

Just out of curio... can you land a probe onto any of the gas giants or would it be crushed? How many of our planets could (wo/)man actually walk on (and would this include the asteroid planets?).

Current tech would have issues on most of the gas giants, high temperatures and in some cases very high radiation is likely not to allow landings there, though at least Wikipedia seems to imply that Venus has the highest pressue of the planets.  Uranus would be the easiest to do it on, its been suggested we could mine Helium-3 there with a possible manned base on one of the moons.  Man could walk on Mars, Mercury (temp on sunny side would be an issue), Venus (Atmospheric pressure about that same as being 3000 feet underwater, so you'd need good gear), plus all 4 Dwarf Planets and most of the moons, asteroids, etc.  
      -Tig

[Tigger]

Hyperspeed wrote:

Interesting is the fictional 'world' of Halo... a weapon/planet who's entire surface is the inner track of a giant ring. Maybe we should start thinking of more designations when technology allows us to make our own worlds or discover things that don't fit the mould!

Thats a steal from Niven's Ringworld, which is a sub idea of Freeman Dyson's shell or as its more commonly known today, a Dyson Sphere.
   -Tig