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IAU Demotes Pluto to 'Dwarf Planet' Status
davidwr writes "It's official. Pluto's been demoted. It's now one of several 'dwarf planets.' I guess we can drop the 'Period' from 'Mary's violet eyes make John stay up nights.'" (Of course, no one says you have to privately agree with the International Astronomical Union.) Several readers have contributed links to the BBC's coverage of the downgrade, as well as the usefully illustrated story at MSNBC.
Quick, someone who actually knows what they're doing, please give me a rough answer/calculation to the following queries:
Pluto is automatically disqualified because its oblong orbit overlaps with Neptune's.
1) - Is it possible for Pluto and Neptune to one day (like within the next couple billion years) collide? Or are their respective orbits degrading to the point where by the time they'd be near each other orbit-wise, their orbits would no longer overlap significantly? Or by 'overlap' do they mean "diagrammatically speaking, on a two-dimensional representation they overlap but even at their closest possible point they're still a squillion miles away from each other"?
2) - If so, how cool would that be? Would it be funny enough to make it onto an America's Funniest Home Videos video montage? Would it need special clown-horn-honking sound effects?
3) - Considering their distance from Earth and their relatively small size, would a collision of the two have any noticeable effect here on Earth?
4) - Seriously, how cool would worlds colliding be?! Costanza jokes aside, I think it'd be awesome to the max.
One thing that annoys me is that they added "is not a satellite" to specifically exclude Charon.
Pluto orbits the sun, but it also orbits a point in space above its surface. Charon doesn't orbit Pluto, but orbits a point in space above the surface of Pluto, while it too orbits the sun. Can someone explain to me why this shouldn't be called a double?
But this Rottweiler not only is snarling and frothing at the mouth; it also went to Harvard.
Not so. The original proposal (which had the "is not a satelite" clause) made Charon a planet.
"is not a satellite" does not exclude Charon, because they picked a somewhat peculiar definition of "satelite" (barycenter of gravity inside the primary), which excludes almost everything we typically think of as a moon, but not Charon. This definition makes the Moon a satelite, but if the Earth had a slightly smaller radius but the same mass, the Moon would follow exactly the same orbital track, but suddenly be a planet.
I beleive they picked this definition of "satellite" specifically to exclude Earths Moon. If you actually plot the orbital tracks of the Moon, Charon, and any other moons you like, one stands out like a sore thumb as the one that should obviously be said to be orbiting the Sun. It's not Charon.
The thing that bothers me is that if Pluto hasn't cleared Neptune out of it's orbit, then neither has Neptune cleared Pluto
I'm assuming for the moment that it was misreported. The real problem with Pluto is the thirteen other known Plutinos -- objects not gravitationally related to Pluto, but also in highly elliptical Neptune-cossing orbits with a 3:2 resonance to the Neptunian orbit.
Now, there are a bunch of objects which have stable solar orbits with a period the same as Mars. But in the case of Mars, they all either orbit Mars itself, Sol-Mars L4, or Sol-Mars L5. Same can be said for Jupiter, Saturn, Uranus, and Neptune (and Earth, except the "bunch", since Earth only really has the Moon).
Instead, Pluto is like Ceres, which has a number of objects in the same orbit which are all more-or-less doing their own thing. Demoting Pluto now that we know about the Plutinos is like the demotion of Ceres after the discovery of a bunch of other asteroids in the same orbit.