Science

shenmue

(38,506 posts) Sat Feb 21, 2015, 11:36 AM Feb 2015

And now, dwarf planet Ceres!

Story here

Ceres is located between Mars and Jupiter. It's the runt of the litter: not big enough to be a full-fledged planet, not a moon either.

From the article:

You read that right. There's a planet between Mars and Jupiter.

You may not have heard of it, but it was discovered in 1801 -- 129 years before Pluto. It originally was called a planet, then later an asteroid and now it's called a dwarf planet.

4 replies

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And now, dwarf planet Ceres! (Original Post) shenmue Feb 2015 OP

hmmmm, wonder if it is related to Cersei Lannister still_one Feb 2015 #1

According to the article, it's "the giant of the main asteroid belt," NaturalHigh Feb 2015 #2

IAU Resolution 5A definitions passed in 2006 William Seger Feb 2015 #3

Thanks for that William. NaturalHigh Feb 2015 #4

still_one

(92,204 posts)

1. hmmmm, wonder if it is related to Cersei Lannister

Reply to shenmue (Original post)

Sat Feb 21, 2015, 11:43 AM

Feb 2015

NaturalHigh

(12,778 posts)

2. According to the article, it's "the giant of the main asteroid belt,"

Reply to shenmue (Original post)

Sat Feb 21, 2015, 01:39 PM

Feb 2015

I guess I'm not entirely clear on why it's labeled a dwarf planet instead of an asteroid.

Still, this is extremely cool, and I'm looking forward to Dawn's visit. It would be great if NASA could study every planet, asteroid, dwarf planet, planetoid, whatever in our solar system, but I'm resigned to accepting that's not going to happen in my lifetime (or probably even my children's'). Maybe a little mystery is better anyway.

William Seger

(10,778 posts)

3. IAU Resolution 5A definitions passed in 2006

Reply to NaturalHigh (Reply #2)

Sun Feb 22, 2015, 01:53 AM

Feb 2015

> I guess I'm not entirely clear on why it's labeled a dwarf planet instead of an asteroid.

It's a result of the new definitions passed by the International Astronomical Union in 2006, which also demoted Pluto to "dwarf planet." Basically, the difference between them and asteroids is that they have enough mass to be "nearly round," but aren't planets because they haven't "cleared the neighbourhood" around them.

(From the article "A recipe for returning Pluto to full planethood" at: http://phys.org/news/2015-02-recipe-pluto-full-planethood.html#jCp )

A "planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape, and (c) has cleared the neighborhood around its orbit.
A "dwarf planet" is a celestial body that (a) is in orbit around the Sun, (b) has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape2, (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.
All other objects, except satellites, orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".

NaturalHigh

(12,778 posts)

4. Thanks for that William.

Reply to William Seger (Reply #3)

Sun Feb 22, 2015, 08:11 AM

Feb 2015

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