why is that pluto is not considered a a planet today?

Answer 1

http://en.wikipedia.org/wiki/Pluto

on 24 august 2006, the international astronomical union reclassified pluto.

pluto does orbit the sun, is ball-shaped and is not a satellite, but it does not have an isolated orbit (a bunch of other similar bodies have similar orbits.) so it is not a planet.

i have been waiting for this since i was about ten when i learned that pluto didn't fit the pattern set by the major bodies in the solar system so it was an anomaly. it just felt "out of place". now that astronomers have found hundreds of other bodies with similar orbits, classifying "134340 pluto" as a planet is even more irrational. i feel somewhat satisfied, but i don't know how long this will drag on tho. many planetary astronomers are satisfied that the definition is rigorous enuf. i can accept that the definition is flawed, but i can not accept that "134340 pluto" is a planet.

this was the right thing to do, believe me. this does not change anything about pluto or the solar system. this just corrects the mistake of classifying pluto as a planet initially.

this same thing happened has happened before. in 1800, an astronomer found a body orbiting the sun between the orbits of mars and jupiter and thought it was a planet. astronomers finally stopped classifying them as planets after they found several other bodies with similar orbits, and no one thinks ceres, pallas, juno, and vesta are planets today.

many astronomers consider pluto and charon to be a binary system, but two small bodies orbit that system. they are called nix and hydra.

incidentally, "134340 pluto" was never a moon of neptune. neptune did capture triton. this is why triton has a retrograde orbit

Answer 2

Pluto isn't considered a planet for a few reasons. First of though we have to define what a planet is and also what a dwarf planet is which is what Pluto is now considered to be.

The International Astronomical Union came up with 4 points that have to be met in order for a body to be classified as a dwarf planet:

a) The body must be in orbit around the Sun;
(b) It must have sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape;
(c) It has not cleared the neighbourhood around its orbit; and
(d) is not a satellite

They also agreed on what a body must be to be classified as a planet:

a)The body must be 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.
(c) has cleared the neighbourhood around its orbit.

Pluto's orbit is another factor that made it clear that its status had to be revised. Pluto's orbit is very eccentric, which means that unlike the other planets that follow a near circular path on their way around the sun, Pluto's orbit is highly inclined. This eccentric orbit actually brings it closer to the sun for a subtanial time during its orbit. Pluto takes 248 years to orbit the sun. During 20 of those years its orbit is within that of Neptune.

The discovery of Eris reignited the debate over Pluto's status. Eris is thought to be part of the solar system known as the Keiper belt which is very similar to the asteroid belt between Mars and Jupiter, but is commonly known as a Trans Netunian Object. If Clyde Tombaugh, the man who discovered Pluto in 1930 had known about the Keiper belt it is very unlikely that he would have classified it as a planet.

If Pluto had kept its planet status it could mean in 30 years time when we discover other bodies like Eris (who like Pluto is now a Dwarf planet) we could have a solar system with 20 or 30 planets orbiting the sun.

Hope this helped you out :)

Answer 3

It was deemed by the International Astronomical Union (IAU) that it was too small and there are larger objects in the Kuiper Belt which was unknown when Clyde Tombaugh discoverd Pluto in 1930. The issue of Pluto being a planet has been ongoing for a number of years but the issue of changing it was tabled until after the death of Clyde Tombaugh in 1997.

Answer 4

Gandolf has a good complete answer.
In easier terms: Pluto is too small, and its orbit is too elliptical.

If it was still a planet, we'd have to add more of them because some asteroids recently discovered are larger than Pluto

Answer 5

in accordance to the hot definition, an entire-fledged planet is an merchandise that orbits the solar and is sufficiently super to are growing to be to be around because of the strain of its very own gravity. besides, a planet has to dominate the community around its orbit. Pluto has been demoted because of the fact it does not dominate its community. Charon, its super "moon," is merely some million/2 the size of Pluto, mutually as all the real planets are a techniques extra advantageous than their moons. besides, bodies that dominate their neighborhoods, "sweep up" asteroids, comets, and different debris, clearing a course alongside their orbits. in contrast, Pluto's orbit is somewhat untidy.

Answer 6

It is too small, now it is considered a dwarf planet...

Answer 7

the reasons are that it is not lage enough to be one, another is that a planet must not cross another planet's path.