[pedonbio]

Since it is June 22 in most of the world, it is worth noting that this is the anniversary of the 1978 discovery of Charon, the first satellite of Pluto, at the U.S. Naval Observatory.

[SwitcherX]

they found 2 more moons around pluto didn't they?

[notty]

That's no moon...

[pedonbio]

they found 2 more moons around pluto didn't they?

Yes, Nix and Hydra, both in 2005. Life was so much more certain when Pluto was a planet...

[SwitcherX]

Yes, Nix and Hydra, both in 2005. Life was so much more certain when Pluto was a planet...

Really.  I mean, it's the dominant body in its orbit, unlike Sedna.

[BarnacleBill]

It's too big to be a space station.

[bignatslover]

Pluto was the first victim of the recession.

[3deroticer]

I kind of remember, that Pluto got a demotion to something. What is it now?

Anyone looking forward to seeing planet Nibiru?

[pedonbio]

It's classified now as a "dwarf planet".

Like many things, we just learned too much over time. It is the second-biggest dwarf planet, the asteroid Eris being bigger.

It's reclassification came about because about twenty years ago astronomers decided to get more precise in their classifications and agreed to come up with a definition for "planet" because the only definition was what it meant in Greek: "wanderer".

So a "planet" has to have three characteristics: 1) It has to have enough gravity to be round; 2) It has to be the dominant body in its system (Our moon is almost as large as Mercury); and 3) It must have cleared its orbit of debris. Pluto meets the first two, but not the third. It has only about a fifth the mass of the moon, so its orbit still has a lot of space junk.

[TheZookie007]

With all the artificial satellites and space junk that Terra has, Pluto should still be considered a planet. The IAU fucked up big-time.

[DruulEmpire]

I miss Planet Pluto -- but not that much.  The concept of "ocean" defined the outer edge of the known world once, so Neptune now being the outermost official planet feels right.

Isn't Charon Jim's girlfriend?

[rtpoe]

With all the artificial satellites and space junk that Terra has, Pluto should still be considered a planet. The IAU fucked up big-time.

Not really.

Given that Pluto was getting smaller and smaller as we got better data about it and its satellites, and we were finding other oddities like asteroids with their own satellites (cf Ida and Dactyl), astronomers were really forced to consider exactly what was meant by the term "planet". Nobody (not even many astronomers) likes what the IAU came up with, but what can you do? Scientists need good working definitions of their major terms...

[homevintner]

I thought Ceres was the largest asteroid. Wasn't it originally classified as a planet, or dwarf planet shortly after discovery?

[CarlTL]

It was briefly classified as a planet when it was discovered on 1 January 1801, but was reclassified as an asteroid after 1802. When they codified the term dwarf planet Ceres was reclassified again as one.

Incidentally, Ceres contains approximately 32% of the entire mass of the asteroid belt between Mars and Jupiter, and may contain some form of water...

[BarnacleBill]

I've heard that Jupiter's moons Io and Europa may have the best chance of having life.  Some believe they may have liquid oceans underneath their frozen outer hull.

we really need 2 start-up deep under water bases where ther's no light (3000 meters below or more) so that we can develop the technology now to colonize the moons later if Al Gore is right.