why did they remove pluto as one of the nine planets?

Question

answer this seriously. it's urgent!

Answer 1

modern scientists have made certain definition of planet. Pluto did not satisfy those definitions. so they removed it from the list.

Answer 2

Pluto was discovered in 1930, and from the outset, its orbit was known to be tilted with respect to the orbits of the rest of the planets, and it also comes closer than Neptune for about 10% of its orbit. With the discovery of other objects beyond Pluto in the region known as the Kuiper Belt, (including one called Eris which is known to be larger than Pluto), there has been a move to reclassify Pluto.
After a study group had been working on this for two years, a proposal for a definition of a planet was put forward at the conference of the International Astronomical Union last August.
This said that a planet was an object orbiting a star, and was not itself a star or a satellite of a planet. Also, it had to have enough mass that gravity had pulled it into a round shape. For this reason, they included Ceres, the largest asteroid, Pluto, Eris and Charon. Charon, formerly regarded as the largest moon of Pluto, was regarded as a planet because Pluto and Charon actually orbit a common point which is above the surface of Pluto. All other moons orbit a point which is below the surface of their primary planet. I think this is a very good criteria.
However this definition was rejected, and a new one was devised in the next few days, and a vote was taken on the last day of the conference. The new definition agreed on only relates to planets in our solar system (I don't know why this limitation was introduced). It added the criteria that a planet must have cleared its orbital neighbourhood. They cut out Pluto & Charon and Eris as there are other objects in the Kuiper belt. Similarly, Ceres didn't qualify as there are other asteroids. Pluto, Eris and Ceres were designated "dwarf planets", though it would have been better to have also labelled Mercury, Venus, Earth & Mars as "terrestrial planets" and Jupiter, Saturn, Uranus & Neptune as "gas giant planets". We would then have three categories, and "dwarf planets" would clearly be seen as part of the overall group. Also, a 3-foot high man may be referred to as a dwarf, and someone 7 feet high as a giant, but they are still both human, so dwarf planets are still planets!
As a result, at the moment we have a total of 11 planets in the solar system: Mercury, Venus, Earth, Mars, Ceres, Jupiter, Saturn, Uranus, Neptune, Pluto and Eris.
Here's a mnemonic for remembering the order:
My Very Educated Mother Can't Judge Symphonies Unless Neighbours Play Euphoniums!

Answer 3

Pluto was removed for simplicity. Astronomers began discovering other bodies in the outer solar system, some of which they believe to be larger than Pluto, and as the number of these objects grew it became clear that to classify them all as planets would create a mess.

So, they came up with a plan to define a planetary body as one, basically, that is nearly spherical, dominates it's place in it's orbit, and orbits in a nearly circular orbit about the sun. Pluto misses out as a planet because it doesn't dominate it's region of the solar system.

Earth nearly misses out as a planet because of the large mass and proximity of the moon..the moon perturbs the orbit of the earth a bit (the reverse occurs, as well), and the orbit of the moon really is an orbit around the sun, perturbed by the presence of the earth. So, the Earth doesn't really dominate it's place in the solar system any more than does Pluto..a point seemingly overlooked by the astronomers. However, the large mass and low orbital eccentricity of the Earth relative to nearby planets saves the day.

Make a diagram, with a circle (the orbit of the earth) of some size around a center (the sun). Now, along the circle make another orbit which, twelve times, about) travels inside and outside the earth's orbit..the distance it travels inside and outside the orbit of the earth is only about 1/400th of the radius of your larger circle: this represents the orbit of the moon about the sun (yes, the sun). You can scarcely notice the presence of these 'waves' in the orbit of the moon: if your earth orbit is 25cm inches across the moon travels 1/400th of that distance, or 0.6mm inside and outside the orbit of the earth.

Answer 4

Pluto has always been on the fence with the heads of astronomy research. The problem is it's not big enough to have been classed as a planet to begin with so years ago they held a conference and adopted Pluto as a planet. Now with the discovery of stellar objects close to size and mass they had to rethink the definition of a planet or risk having to adopt and asteroid and a satellite plus our moon as planets.

Answer 5

It was too small to be categorized as a "planet".

Answer 6

isn't it too small or something? or they reckon it's a moon of neptune or uranus (which ever one is next to it).