What was the reason for the demotion?
2006-09-09 09:18:59 · 14 answers · asked by John G 5 in Science & Mathematics ➔ Astronomy & Space
No, it doesn't fit the definition and here is why it should NEVER have been counted as a planet even when first discovered.
1st -Its orbit is very odd relative to the other planets. Its orbit varies above and below the plane of the solar system and it also sometimes crosses the orbit of Neptune.
2nd - They are finding objects larger in the Kupier Belt that are larger than Pluto. If they make these planets also, we may have over 50 planets in the next 10 years.
3rd - Its center of gravity is "shared" with its "moon" Charon. Meaning Pluto and Charon kinda rotate around each other in a weird orbit.
Also, Pluto isn't the first demoted planet. The current largest asteroid in the asteroid belt between Mars and Jupiter is Ceres. Ceres was once considered a planet in the late 1800's before it was also demoted.
2006-09-09 09:25:30 · answer #1 · answered by T F 3 · 0⤊ 0⤋
There are many good reasons to consider Pluto a comet and not a planet that have already been touched on (the center of mass isn't so important... the moon-Earth system have a center of mass a long ways off of the center of the Earth that we revolve around). It is a Kuiper Belt object as far as we can tell and that's really the best reason.
Why it was "demoted" is because in the new definition of a planet, a planet must be three things...
It must revolve around the Sun (which pluto does)
It must have enough mass (therefore gravity) to be overall ball shaped (which Pluto is)
It must have cleared it's path of objects of similar size (which Pluto has not because it is part of the Kuiper Belt. All other planets have clear paths except for moons that are much smaller than them, except the Earth but our moon was once part of the Earth.
Objects that fit the first two and not the third and are not moons of planets are now called dwarf planets.
2006-09-09 12:04:11 · answer #2 · answered by iMi 4 · 0⤊ 0⤋
Actually, only four planets really fit the IAU definition of a planet.
IAU's official definition:
(1) 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 neighbourhood around its orbit.
Earth, Mars, Jupiter and Neptune do not meet the third criterion. Ever heard of a Near-Earth Asteroid? There are thousands of them, every year more are discovered. They cross Earth's orbit and occasionaly threaten to hit the Earth or Moon and often pass directly between the two.
Mars and Jupiter have the same problem.
Pluto crosses Neptune's orbit, if Pluto is demoted, Neptune should follow. Also Neptune contends with a bunch of random iceballs which cross it's orbit.
So welcome to the new Solar System
Planets = 4 (Mercury, Venus, Saturn and Uranus)
2006-09-09 11:25:22 · answer #3 · answered by April C 3 · 0⤊ 0⤋
no, pluto is not a planet. the international astronomical union defined "planet" with a vote on 24 august 2006. i don't know how long this will drag on tho. many planetary astronomers are not satisfied that the definition is rigorous enough. this same thing happened in the early 1800s after astronomers discovered several bodies between the orbits of mars and jupiter. they finally stopped calling them planets after the discovery of the fourth one.
i have been waiting for this since i was about twelve because i knew that pluto does not fit the pattern set by the major bodies in the solar system.
http://www.iau.org/fileadmin/content/pdfs/Resolution_GA26-5-6.pdf
2006-09-09 09:37:33 · answer #4 · answered by warm soapy water 5 · 0⤊ 0⤋
My current reading of the Pluto question is whatever governing body of science that names astronomical events and whatever else is out there... has deemed Pluto to be a planetoid. There is currently a large debate as to whether or not Pluto should be re-instated as a planet. The arguement being... if Pluto isn't a planet... but isn't a moon... why aren't all the other moons in our solar system also called planetoids... when they're meetingthe same criteria
2006-09-09 09:23:33 · answer #5 · answered by Mouse 1 · 0⤊ 0⤋
The size pluto demoted it to a dwarf planet status.
2006-09-09 09:22:26 · answer #6 · answered by Ryt d 2 · 0⤊ 0⤋
It use to fit the definition of a planet. It still does. You can't go backwards on the definition of a planet.
2006-09-09 09:23:06 · answer #7 · answered by tysavage2001 6 · 0⤊ 0⤋
no, it is too small to be a planet, and if it got as close to the sun as earth is right now, then it would have a tail like a comet. but, that's just the science, and personally i think it is planet.
2006-09-09 09:23:07 · answer #8 · answered by lovebug 1 · 0⤊ 0⤋
no its to small. smaller than our moon. if we accept it as a planet then we will hav to accept our moon as a planet too. also its mass is not large enough to overcome the efective gravitational attraction to other bodies. at least that much i know
2006-09-09 09:33:04 · answer #9 · answered by matola 2 · 0⤊ 0⤋
I guess the planet was too small or something...
I believe it doesnt fit
2006-09-09 10:51:46 · answer #10 · answered by mana 1 · 0⤊ 0⤋