IAU Demotes Pluto to 'Dwarf Planet' Status 426
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.
So why does Neptune qualify? (Score:5, Interesting)
Re:So why does Neptune qualify? (Score:1, Interesting)
And how is this definition supposed to apply to "planets" detected around other stars, where recognizing whether or not the body has "cleared the neighborhood around its orbit" is especially challenging? I assume the technical definition must have a detailed specification of what constitutes a "clear neighborhood" in the orbital sense.
Re:Astrologers panic! (Score:1, Interesting)
Teaching about Pluto in School (Score:3, Interesting)
I got in similar trouble to telling my teacher that her solar system model was wrong because all of her planets were on the same plane. And, got in more trouble when I mentioned that Pluto is not the furthist planet from the sun, but rather Neptune was (at least, at that time). Of course, the worst was when I corrected a teacher whom said Saturn was the only planet with rings.
Anyone? Anyone? (Score:4, Interesting)
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.
Amateur Night In Prague (Score:2, Interesting)
In programming terms, the function:
bool Is_Planet( Astronomical_Object* foo );
, does not yet exist. Well, under some proposals, it would have existed in the following form:
bool Is_Planet( Astronomical_Object* foo ){
return (Is_Kinda_Big(foo) && Is_Kinda_Spherical(foo));
}
Great. Let's have a big round of applause of the boys at the IAU. Seriously, an eight year old could have come up with this. "Well, it's kinda round!". What if it's elliptical? What if it's a cylinder? Elliptical cylinder? What about Dyson Sphere's? Ringworld's? What if it has bumps? Depressions? Great big crater holes? Gentlemen What about the Death Star?
500+ years of modern astronomy and still no definition for a planet. Is this professionalism? Look at the difference in comparision to other scientific fields. The SI [wikipedia.org] units give precise, unambiguous definitions of every observable quantity in the universe. Can we get something similar in astronomy please?
OK, I'm ranting, but here's somthing that astronomers can really chew over. Is their definition of a planet falisfiable? If not, are they really scientists, or just stargazers?
Re:my take on it: (Score:5, Interesting)
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?
Re:my take on it: (Score:2, Interesting)
C+ - Very sloppy work
Re:my take on it: (Score:2, Interesting)
Now about that definition - in my very naive view, shouldn't the definition of "planet" have something about the body in question orbiting in the plane of the star's equator? I think that would go a long way towards differentiating captured comets, asteroids, etc. from the "classically" formed planets.
Can someone explain why that doesn't make sense?
Re:my take on it: (Score:4, Interesting)
"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.
Re:my take on it: (Score:3, Interesting)
They claimed to exclude Charon from being a dwarf planet, so they're obviously not using the barycenter definition to determine what a satellite is.
Re:my take on it: (Score:4, Interesting)
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.