Pluto - Not a Planet?

[ronthepon]

What nonsense, BD, how can you possibly hope to hit a sweet shot with a driver without a golf cart?:cup:

[ronthepon]

BTW, when is this news going to get really out in the open?

 

I mean reach the text books kind.

[CraigD]

If I am standing on some object in space, and I am at rest on the surface of that object, and I tee up a golf ball and crank a sweet shot with a driver, and the ball reaches the escape velocity of that object.... then I am not standing on a planet.

The 3 new planets per the IAU draft, Ceres, Charon, and “Zena”, remain planets under the “sweet golf drive” criterion. Their escape velocity are about 510, 580, 500, and 1200 m/s. The world’s best golf drive is a little under 500 m, which, ignore air friction, requires about a 70 m/s initial velocity.

 

A quick survey of moons shows that the SGD and the IAU “enough gravity to be round” criteria give nearly the same classification. Ignoring that some of them are clearly moons, not planets (by the draft proposal’s “barycentre resides outside the primary” criteria), here are a few bodies on the border of planet/not planet:

Mimas, moon of Saturn. Escape velocity: 160 m/s (about 2 SGDs) :cup: Looks: spherical :(

Miranda, moon of Uranus. Escape velocity: 79 m/s (1.1 SGDs) :shrug: Looks: raggedly spherical :shrug:

The asteroid Vesta. Escape velocity: 35 m/s (0.5 SGDs) :thumbs_do Look: like a lumpy raisin :thumbs_do

 

What an odd coincidence, that a gravitational/hydrostatic criteria like EGTBR and one based on the athletic ability of Earth’s top ape vs. gravity like SGD should give such similar results.

 

I have another criteria proposal. “A planet is a celestial body that (a) has a listed purchase price of over 100 Fedrons in the boardgame ”Solarquest”, and (B) is in orbit around a star, and is neither a star nor a satellite of a planet.” This would transfer ultimate control and responsibility for the definition from IAU to the Hasbro toy company. ;)

[CraigD]

I heard that there was a possibility that pluto was once formed as a moon around neptune, and flung out by some interaction.

I’ve heard the same speculation. I don’t think it stands up to scrutiny, because:

• For Pluto to have been transferred from an orbit around Neptune (or any other planet) into its present orbit, would have required both a large change in velocity at the beginning of the transfer (eg: a gravitational yank from a near miss from a massive intruder body), and a similarly large yank at the end. The probability of 2 such improbable events occurring seems slim
  
• Pluto has a satellite/double planet companion, Charon. The probability that it could Charon could have formed independently of Pluto, and been captured after it was ejected from Neptune orbit, or that both could have formed around Neptune, and remained in mutual orbit after being ejected, seems slim
  

Though moons being ejected into low-eccentricity orbits around the Sun may be unlikely, objects in high-eccentricity orbits around the sun being captured by the giant planets has likely happened quite a bit. Triton, which is larger than Pluto, is thought to be a kuiper object captured by Neptune. Amalthea appears to be an asteroid captured by Jupiter. Many of the lesser satellites (eg: Lesser satellites of Uranus – scroll down 1/2 page) may be captured kuiper object, or, in the case of Jupiter, asteroids. Smaller planets also appear to capture moons - the 2 little moons of Mars are believed to be captured asteroids.

[InfiniteNow]

I hear that the Big Boys & Girls (IAU - International Astonomers Union) are in Prague hashing out an official answer to the "is Pluto a planet" question as we post.

http://www.iau.org/

So... would this be considered a "plutocracy?" Oh, yes I did! :)

[InfiniteNow]

And all this just ruins the sweet little mnemonic device I'd learned:

 

My

Very

Educated

Mother

Just

Said

Uh-oh

No

 

PLUTO!

[TheFaithfulStone]

I like "sweet golf drives" better.

 

Very Napolean Dynamite.

 

"That's an awesome planet. Do you ever hit sweet golf drives off it?"

 

"No? Gahh!"

 

TFS

[CraigD]

Why let the pros in the IAU have all the fun?

 

Let’s have our own up/down vote on the IAU draft resolution!

 

Go to 8038 and vote before 9:00 EST Saturday!