why pluto is no longer a planet?

Question

because it is a moon and the sollar system is only 8 not 9

Answer 1

Pluto is too small, has an irregular orbit, and it now appears that there are dozens of these type of bodies, bigger than Pluto, but made of the same stuff, all floating in the Kuipper Belt. At some size and material point they had to draw the line and so the question is "Are there 8 planets ot are there 42 planets?" For education purposes, 8 makes sense.

Answer 2

Pluto is now called as a dwarf planet..This has been debated months back because they insisted that if Pluto was to be a planet, then we should also consider 53+ other small planets around Jupiter, which would sum up to more than 60+ in the solar system. Therefore it is agreed that we classify Pluto as a dwarf planet along with the others.

Worry not, because PLUTO now spans into a verb and an adjective, and it was recently recognized as the 2006 Word of the Year by the American Dialect Society.

To “pluto'' is “to demote or devalue someone or something'' much like what happened to the former planet last year when the General Assembly of the International Astronomical Union decided Pluto did not meet its definition of a planet.

So i guess you'll be hearing more about pluto more often now than before.

Answer 3

The decision [to demote Pluto to a dwarf-planet] establishes three main categories of objects in our solar system.

1. Planets: The eight worlds from Mercury to Neptune.
2. Dwarf Planets: Pluto and any other round object that "has not cleared the neighborhood around its orbit, and is not a satellite."
3. Small Solar System Bodies: All other objects orbiting the Sun.

Pluto and its moon Charon, which would both have been planets under the initial definition proposed Aug. 16, now get demoted because they are part of a sea of other objects that occupy the same region of space. Earth and the other eight large planets have, on the other hand, cleared broad swaths of space of any other large objects.

From: http://space.com/scienceastronomy/060824_planet_definition.html

Answer 4

Because Pluto is the only planet discovered by an American and the world hates America !

Answer 5

Planetary status controversy
Pluto's official status as a planet has been a constant subject of controversy, fueled by the past lack of a clear definition of planet, since at least as early as 1992, when the first Kuiper Belt Object, (15760) 1992 QB1, was discovered. Since then, further discoveries intensified the debate in the 21st century.

Omission from museum models
Museum and planetarium directors occasionally created controversy by omitting Pluto from planetary models of the solar system. Some omissions were intentional; the Hayden Planetarium reopened after renovation in 2000 with a model of 8 planets without Pluto. The controversy made headlines in the media at the time.

New discoveries ignite debate
Pluto compared to Eris, (136472) 2005 FY9, (136108) 2003 EL61, Sedna, Orcus, Quaoar, and Varuna compared to Earth (artist's impressions; no detailed photographs exist).
Pluto compared to Eris, (136472) 2005 FY9, (136108) 2003 EL61, Sedna, Orcus, Quaoar, and Varuna compared to Earth (artist's impressions; no detailed photographs exist).

Continuing advances in telescope technology allowed for further discoveries of Trans-Neptunian objects in the 21st century, some of comparable size to that of Pluto. In 2002, 50000 Quaoar was discovered, with a diameter of 1,280 kilometres, about half that of Pluto. In 2004, the discoverers of 90377 Sedna placed an upper limit of 1,800 kilometres on its diameter, near Pluto's diameter of 2,320 kilometres.

On July 29, 2005, a Trans-Neptunian object later named Eris was announced, which on the basis of its magnitude and simple albedo considerations is assumed to be slightly larger than Pluto. This was the largest object discovered in the solar system since Neptune in 1846. Discoverers and media initially called it the "tenth planet", although there was no official consensus at the time on whether to call it a planet. Others in the astronomical community considered the discovery to be the strongest argument for reclassifying Pluto as a minor planet.

The last remaining distinguishing feature of Pluto was now its large moon, Charon, and its atmosphere; these characteristics are probably not unique to Pluto: several other Trans-Neptunian objects have satellites; and Eris' spectrum suggests that it has a similar surface composition to Pluto, as well as a moon, Dysnomia, discovered in September 2005. Trans-Neptunian object 2003 EL61 (nicknamed "Santa") has two moons (one of which is nicknamed "Rudolph") and is the fourth largest TNO behind Eris, Pluto, and 2005 FY9 (nicknamed "Easterbunny").

IAU Decision
The debate came to a head in 2006 with an IAU resolution that created an official definition for the term "planet". According to this resolution, there are three main conditions for an object to be considered a 'planet':

1. The object must be in orbit around the Sun.
2. The object must be massive enough to be a sphere by its own gravitational force. More specifically, its own gravity should pull it into a shape of hydrostatic equilibrium.
3. It must have cleared the neighbourhood around its orbit.

Pluto fails to meet the third condition. The IAU further resolved that Pluto be classified in the simultaneously created dwarf planet category, and that it act as prototype for a yet-to-be-named category of trans-Neptunian objects, in which it would be separately, but concurrently, classified.

Impact of the IAU decision
There has been resistance amongst the astronomical community towards the reclassification, dubbed the "Great Pluto War" by some astronomers. Alan Stern, principal investigator with NASA's "New Horizons" mission to Pluto, has publicly derided the IAU resolution, stating that "the definition stinks" albeit "for technical reasons." Stern's current contention is that by the terms of the new definition Earth, Mars, Jupiter and Neptune, all of which share their orbits with asteroids would be excluded. However, his own published writing has supported the new list of planets, as "our solar system clearly contains" eight planets that have cleared their neighbourhoods, however, he does not deny planetary classification to objects like Pluto & Ceres that have not "cleared their neighbourhood". Marc W. Buie of the Lowell observatory has voiced his opinion on the new definition on his website and is one of the petitoners against the definition. Others have supported the IAU. Mike Brown, the astronomer who discovered Eris, said "through this whole crazy circus-like procedure, somehow the right answer was stumbled on. It’s been a long time coming. Science is self-correcting eventually, even when strong emotions are involved."

Among the general public, reception is mixed amidst widespread media coverage. Some have accepted the reclassification, while some are seeking to overturn the decision, with online petitions urging the IAU to consider reinstatement. A resolution introduced by some members of the California state assembly light-heartedly denounces the IAU for "scientific heresy," among other crimes. Others reject the change for sentimental reasons, citing that they have always known Pluto as a planet and will continue to do so regardless of the IAU decision.

The words "plutoed" and its variant "to pluto" were coined in the aftermath of the decision. In January 2007, the American Dialect Society chose "plutoed" as its 2006 Word of the Year, defining "to pluto" as "to demote or devalue someone or something", an example being "as happened to the former planet Pluto when the General Assembly of the International Astronomical Union decided Pluto no longer met its definition of a planet."

Answer 6

It's actually a "dwarf planet" now. They changed it because if it was considered a normal planet, future generations of kids would have to learn a LOT more planets

Answer 7

maybe.........it doesn't meet the qualifications in order to be a planet