Why was Pluto said to no longer be a planet?

Question

How many planets are there now? Were there any more added?

Answer 1

Nearly every schoolchild who has grown up in the latter part of the 20th century has been taught that Pluto was not only the furthest planet from the Sun, but also the smallest in our solar system. For now, science books and astronomical charts will have to be revised due to a decision made by the International Astronomical Union (IAU) during a meeting in 2006. The decision, which included eight days of zealous debate and a nearly split vote, resulted in Pluto being unceremoniously downgraded to a dwarf or minor planet status. Stripped of its “classic” planet status, Pluto is now what amounts to a third class citizen in our solar system.

It’s not so much that Pluto was intentionally removed from the classification, but rather that the IAU outlined a new definition of what constitutes a classic planet. Pluto no longer meets the standards. Now, the list of classic planets in our solar system includes Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

The new standards dictate that, to be a classic planet, an object must be a celestial body orbiting the sun, with enough mass to allow itself gravity to form into a round shape. In addition, its gravity should be sufficiently strong to prevent anything from floating around the planet. The term that the IAU used was “clearing the atmosphere,” which was one of the most important aspects of the definition that was debated.

Although Pluto is now a dwarf planet, it also belongs to a third class of “lesser” objects that orbit the sun. The term used to describe Pluto is “smaller solar system body,” which can also be used to refer to comets and asteroids. One would think that because Pluto was downgraded from being the smallest of the planets, it would at least be the largest of the dwarf planets. This is not the case, as UB313, an icy object found further out than Pluto, is the larger of the two.

Regardless of the hot debate that has been raging since the 1990s, the National Aeronautics and Space Administration (NASA) felt that Pluto rated further study. In early 2006, NASA dispatched the New Horizons craft to further investigate the dwarf planet. It is expected to arrive sometime in 2015. Some astronomers who were unhappy with the IAU’s decision believe that the decision to downgrade Pluto will be overturned by then.

The conference, which included approximately 2,500 astronomers representing 75 countries, cast the vote amidst strong opposition. Some astronomers lament the fact that only 5% of the world’s astronomers took part in the decision to change the definition and believe that it will not stand as a result. Strong opposition came from the family of Clyde Tombaugh, the American who discovered Pluto in 1930 in Flagstaff, Arizona, as well as many other astronomers worldwide. For some, the decision was the correct one, as they believe that the original classification of Pluto watered down the definition of a planet.

Answer 2

There are now 8 planets. No more were added.

They removed Pluto because they were trying to objectively decide what should be considered a planet and what shouldn't. If they included Pluto, then they would have to include many other rocks floating around out there. One day, they would even have to call our Moon a planet!

Obviously that doesn't make sense, so Pluto got the boot.

Answer 3

Pluto is not a planet anymore. Should we cry or should we party? I say Party! Planets can be grouped into two categories, Major Gas Giants and Minor Terrestrials. The Gas Giants are in the outer part of the Solar System and include Jupiter, Saturn, Uranus and Neptune. The Terrestrials are in the inner part of the Solar System and include Mercury, Venus, Earth, Mars, along with what use to be a planet and is now the asteroid belt. Where does Pluto fit into either of these classifications? Pluto is a minor piece of ice and other debris left over from the formation of the Solar System 4.7 billion years ago. It belongs to that group loosely labeled "The Oort Cloud", and that is where it belongs. If life had developed on Jupiter or one of the other Gas Giants, we might be discussing whether the Earth and other Terrestrials were "planets", but let's not go there right now.

Answer 4

There are now 8 planets. No more were added, but there is now a classification of "dwarf planets" under which Pluto falls along with Charon (Pluto's moon) and Ceres (one of the largest asteroids in the belt between Mars and Jupiter. Pluto is no longer considered a planet because of the new definition of a planet which is "a celestial body that is in orbit around the sun, has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a ... nearly round shape, and has cleared the neighborhood around its orbit."

Answer 5

http://en.wikipedia.org/wiki/Pluto
http://www.iau.org/fileadmin/content/pdfs/Resolution_GA26-5-6.pdf

on 24 august 2006, the international astronomical union reclassified pluto. there are eight planets in the solar system: mercury, venus, earth, mars, jupiter, saturn, uranus, and neptune.

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.

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.

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 enuff. i can accept that the definition is flawed, but i can not accept that "134340 pluto" is a planet.

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 6

There was 9 planets in our solar system,but now there are 8.They think Pluto is a meteorite or an astoroid.They also said it is too small and cold to be a planet.And before Pluto was not a planet,some astronomers thought they discovered a tenth planet,called Sedna and it is smaller than Pluto and it is -400 degrees there.

Answer 7

Because Pluto is too small (about the size of USA), and if things like Pluto would be a planet, then we'll have a lot of planets because there's also more things like that and are bigger than Pluto, and they also circulate the sun.
Hope you understand my answer, I'm not very good at explaining

Answer 8

calm down. even if replaced into determined about the definition of a planet, what you grew up with would not be authentic. different gadgets like Pluto, a minimum of one larger and numerous different somewhat smaller, were got here across. there have been both going to be 13 or extra (and turning out to be) planets, or 8 planets and a turning out to be kind of dwarf planets.

Answer 9

This question was asked many times. It is OK to ask it again. Different people may want to see the question from a different angle.

Actually, this (my "answer") is a test to see if we can link to an earlier yahoo question.

Answer 10

I think its because it doesn't have a definite orbit.