why pluto is now not considered as a planet?

Answer 1

the international astronomical union defined three terms "planet", "dwarf planet", and "small solar system body". this does not change anything about the solar system or pluto. it just corrects the mistake of classifying pluto as a planet initially


because pluto orbits the sun, is round, does not have an isolated orbit (a bunch of other similar bodies have similar orbits.), and is not a satellite it is a dwarf planet.

i have been waiting for this since i was about twelve. i feel somewhat satisfied. this was the right thing to do, believe me. i don't understand why so many are having such a problem with this.

(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 neighborhood around its orbit.

(2) A "dwarf 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, (c) has not cleared the neighborhood around its orbit, and (d) is not a satellite.

(3) All other objects orbiting the Sun shall be referred to collectively as "small solar system bodies".


look here:
http://en.wikipedia.org/wiki/Kuiper_belt

Answer 2

It have been known for decades that at some point Plutos position of a planet would be in Jeopardy. It was going to happen when another Pluto size object was found in the Kuiper belt. Pluto is a Trans-Neptunian object (TNO) in the Kupier Belt. For years astronomers have known this, it has just kept planethood because no others were know. Yet we all knew that it was just a matter of time. So Pluto is has it has been known by professional and amateur astronomers for years a TNO.

Pluto is different then other planets in quite a few ways. First Pluto is on in inclination to the planetary plane. That is high compared to the “real” planets. The other 8 planets lie on roughly a plane as you compare their orbits around the sun. Pluto is inclined on this plane by about 16 degrees. Pluto also have a very eccentric orbit, it is such an ellipse that it is closer to the sun for a short period of it orbit (this is many years) then Neptune it this is the reason why it’s a “trans-Neptunian “ object and not just a Kuiper belt object. Also Pluto is very small, when compared to all other planets then Mercury. Had Pluto been found to be a planet on size alone the argument might have been made that out own moon “Luna” is also a planet as the moon orbit’s the sun and not the earth, we only put a small scallop in it’s orbit so tha at some points it’s close the to the sun then the Earth and at other points it farther. Because of Plutos Size, orbit outside the planetary plane, and eccentric orbit Pluto has always been an “odd ball” planet. If Pluto had been found to be a planet along with all the other several hundred predicted objects yet to be found similar to Pluto, we would probably have to make a sub group of planets that describe the first 8 as they do have additional charticersiats that make the similar that other Kuiper belt and Trans-Neptunian objects don’t have.

I have always thought the professional astronomers who wanted Pluto and other Trans-Neptunian objects to be classified as plants all had a desire or at least the opportunity to discover a new planet. As defined now the chances of a new planets being discovered are very remote.

Answer 3

Pluto was discovered in 1930 by a scientist called Clyde Tombaugh. At that time, because there were no powerful telescopes to see it, Pluto was thought to be bigger than earth. But when powerful telescopes became available later, they showed that it was much smaller than our own moon.


Pluto’s diameter is 2,360 km or 1,467 miles, but our moon’s diameter is 3476 km or 2,140 miles. Pluto is also egg shaped and its orbit cuts across Neptune’s.

But the reason for sending Pluto out from the planet group is not exactly this. Since 1990, scientists have discovered a lot of smaller objects in the Kuiper Belt and three years ago, they found an object much bigger than Pluto. It has no names, so the scientists of California University, who were the first who saw it, called it 2003UB313.

After this object was discovered, astronomers asked an important question: if there is an object bigger than Pluto in the Kuiper Belt, then is it right to call Pluto a planet? So, they felt that it is only correct to include it with the objects in the Kuiper Belt.

The International Astronomical Union (IAU), which is the world’s largest group of scientists observing space, finally decided to discuss the matter in their special meeting, which was conducted in the city of Prague last month.

The scientists had two choices. They should exclude Pluto and declare that there are only eight planets. Or they should include 2003UB313 along with two more objects and make the number of planets as 12. When they sat for the meeting, there was tension all around. Nobody, not even the scientists, could say at that time what would happen to Pluto.

In the end, the scientists have created certain rules for planets. What are they? First, a planet must circle the sun. It must be large and round shaped and it must clear other objects from its orbit. Since Pluto did not match these rules, they decided to exclude it from the planet group. Along with two other icy objects in the Kuiper Belt, Pluto is now called a ‘Dwarf Planet’. Yes, many of you are asking what is a ‘Dwarf Planet’, right?

Just like shorter boys are separated in class, Pluto is also separated from the eight big ones and joined with the smaller objects. These smaller objects can’t be compared with the big ones, but then, they also circle the sun. So, scientists have chosen a different name for them– ‘dwarf planets’.

Answer 4

It is not considered a Major planet because of the following:
1. Its orbit is outside of the ecliptic: ie the path that all of the other planets rotate about the sun. The rest are like all within a 6 or 7 degree arc; i think. someone out there help me on that. i don't have time for the research.
2. It varies in its orbital path so that it skims inside of Neptune's orbit.
There may be additional reasons for reclassifying Pluto as a 'Dwarf' planet, but I don't recall what those may be and I think that is getting too close to 'Snow White'. (!)

Answer 5

because scientists found lots of other objects in the past years that are just like pluto. (eliptical orbit, small size, far from sun, etc)

Rather than add planets and continue to add more as they are found, scientists decided to drop pluto as a planet and classify it with the other objects that are now known to be orbiting the sun outside of the 8 major planets.

Answer 6

Because they found many objects much like it in the sky. The outer rim of the solar system if littered with things larger or the same size as pluto. They made it a "dwarf planet".

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

Answer 7

a precise definition for the term planet was decided upon and Pluto did not fit in that description

Answer 8

It must be because of the fact that some of its properties do not fall anymore under the characteristics of a planet.

Answer 9

because other rocks in our system are bigger than Pluto, so to make it distinct, it is now called a dwarf-Planet.

Answer 10

Because we realized it wasn't one after all......