why is pluto not a planet 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, orbits the sun with a bunch of other similar bodies with similar orbits, and is not a satellite it is a dwarf planet.

(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://www.iau2006.org/mirror/www.iau.org/iau0603/index.html

Answer 2

During a recent meeting Society of astronomers have changed the definition of a planet. To be considered as a planet the body has to have certain mass to keep its orbit nearly circular. It has now been established that Pluto fails to qualify as a planet in this regard. If we have to retain Pluto as a planet, we need to consider another 12 objects which are waiting to be qualified all of the size comparable to Pluto. Hence Pluto which was considered a planet since its discovery in 1930 is no longer so today.

Answer 3

In the new deffinition it has to do with Pluto not having "cleared its orbit"

A planet now must meet three critria - in laymans terms

1. Be of enough mass to have formed ona sphrical type shape
2. Not be a moon of another planet
3. Have cleared it's path around it's orbit.



Pluto does fit the first two cirtia for a planet, but Pluto is part of the Kuiper belt. There are many other Pluto like objects and many many smaller type objects orbiting int he same area Pluto does. Since Pluto is part of the Kuiper belt it has not "cleared its orbit" so it does not qualify as a planet.

Answer 4

Because it does not have "control" over Charon, which used to be considered the moon of pluto.

They found out that Charon does not orbit Pluto. The two objects revolve around EACH OTHER, so that the Center of Gravity of their byad system is outside the diameter of Pluto, not inside.

(In the distant future, as our own Moon of Earth, drifts farther away from us, the same will be true for us.}

Rather than upgrading Charon to Planet, they downgraded Pluto to Dwarf Planet, along with the asteroid Ceres, and the distant object "Xena".

Also, besides Xena, they estimated dozens of similar dwarf objects, so it would have been very messy to have about a hundred or more planets!!

Answer 5

The reason is that the IAU (International Astronomical Union) did not want to keep adding planets to our solar system as new ones were discovered. So based on a personal preference (and not science) they created a definition that was meant to exclude Pluto and other similar bodies.

But according to their definition, there are now only two planets in the universe. This is because they define planet as "orbiting the Sun". But there are other stars with planets!

The only two objects that meet the new definition are Mercury and Venus. Earth fails because it has not "cleared its neighborhood" of asteroids and other objects. Jupiter fails for the same reason. So do Mars, Saturn, Uranus, and Neptune.

So according to some astronomers in France, there are now only two planets in the universe.

Here is the definition that they accepted:

The IAU...resolves that planets and other bodies in our Solar System be defined into three distinct categories in the following way:
(1) A "planet" [1] 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.

(2) A "dwarf planet" or a planetoid 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 [2], (c) has not cleared the neighbourhood around its orbit, and (d) is not a satellite.

(3) All other objects [3] orbiting the Sun shall be referred to collectively as "Small Solar System Bodies".

You can see the logical flaws immediately.

Answer 6

Because some astronomers got together and voted on it at the general assembly of the IAU. Curiously, only about 10 percent of the astronomers attending (from about 78 different nations) actually bothered to vote. There is still a great deal of debate going on about the "official" definition of a planet in all circles of life. It's looking like Art - you know art when you see it, but you can't define it to the satisfaction of everyone!

If you want to consider it a planet, that is fine. Many astronomers still consider Pluto to be a planet, but many don't. I think only time and history will ultimately determine the "right" answer, if there is one.

Answer 7

I think it boils down to just an old fashioned turf war. Pluto is a lot smaller than our own Moon, as well as some of the other moons in the solar system, including Titan, Io, Europa, Ganymede, Callisto, among others. Furthermore, it's orbit is kind of wacko compared to the rest of the solar system, and it even has the audacity to come closer to the sun than Neptune(!) during part of it's orbit. This kind of produces an embarrassment for the rest of the larger solar system bodies, who have difficulty tolerating one so markedly different from the rest. I believe these moons got together, formed a lobbying group, and petitioned the International Astronomical Union (IAU) to withdraw and revoke Pluto's license as a bona fide planet. They recruited other political forces to their cause, especially Mercury and Venus, who have always been known as "inferior planets", and these were sore to beat up on someone else and Pluto was looking very vulnerable, we must admit. Neptune was insulted by Pluto's orbital transgressions (you just DO NOT cross the orbit of one of your neighbors, REALLY NOW!) The other major solar system bodies gave no serious objections. So like most things in our world today, it just boils down to jealousy, power mongering, and selfishness, if you want my opinion.

Answer 8

Maybe the Catholic church has decided to reduce the number of planets to the same number that existed, when Galileo discovered that there were more than 7 planets.

They forced him to recant his discoveries and stated that the number 7 is a holy number and even if there are more than 7 planets, there are not.

If Pluto is not a planet, it certainly fits the definition of one. It orbits the sun, just like the other planets.

I wonder which planet they will discredit next, to get that number back to 7.

George Orwell: "He who controls the past, controls the present, He who controls the present, controls the future.
you are seeing it all happen now right before your eyes.

Answer 9

I think they found another mass that is larger with moons and orbits the sun independantly where Pluto crosses paths with the orbit of another planet.

Answer 10

Neptune bitched to the Planetary Commission about Pluto cutting off part of its orbit and the Commission decided to punish Pluto by stripping it of it's planetary rights.


Doug