Why is Pluto no longer considered a planet?

When is the planet not a planet? What makes Pluto like astronomers are fighting? Big Bang blog checks abandoned regret in the solar system

Discovered in 1930, Pluto has been called the ninth planet of the solar system, Pluto is the smallest "planet the furthest, coldest day of the year." In 1978, American astronomer James Christi and Robert Harrington said Pluto had a satellite They discovered that they were, they named it Cathy. The card is about half the size of Pluto and shares the same track. Thus Pluto and Cathy are essentially double planets. Two other satellites, Hydra and Nix, were discovered in 2005

The origin and identity of Pluto has plagued astronomers for a long time. In the 1950's, people now think Triton is its biggest monthly satellite knocking its orbit, Pluto is the fugitive of Neptune's moon. However, since Pluto is not really close to Neptune in practice, this theory has been severely criticized.

In 1992, astronomers started to discover a large number of small ice outside Neptune, and not only Pluto but also the size and composition on the track are similar. Known as Kuiper Belt, this belt is considered the origin of many comets. Astronomers now believe that Pluto is the largest known Kuiper belt (KBO). Like other KBOs, Pluto and the comets share the same function as solar wind blows the surface of Pluto into space in the form of a comet.

Many people who discovered the relationship between the Kuiper Belt and Pluto wondered if Pluto could be considered apart from others in their population. In a nutshell - Is Pluto really a planet?

One of the criteria classified as a planet is that the object needs to "wipe out the neighborhood around its orbit". The mass of the earth is 7 million times the mass of other objects on orbit. Unfortunately, the mass of Pluto is only 0.07 times the mass of objects on other orbits. For this reason, on September 13, 2006, Pluto was officially downgraded to "Planet of the Dwarf".

In the past Neptune, the planet of the alien is "a thousand freezing world, and Pluto is one of them." In fact, Pluto is no longer classified as a planet, but Pluto as Pluto 134340, one of Pluto, many TNO (Trans Neptune is an object) 1. In order to find so many TNOs, there are even bigger (Ellis) when some of the pluto and TNO etc, when found nearly the same size, astronomers can choose. Every planet, or planet, from that classification downgrades Pluto and calls them. 16 Then you can see the spherical Orte Nebula surrounded by the solar system. But this is primarily to explain why comets did not evaporate for billions of years - see comets - destiny or youth indicators? However, this Oort cloud has many scientific problems, Tyson acknowledges that it is not, and can not truly be seen

More than 10 years ago, Pluto was considered the ninth planet of the sun. After over 60 years of discovery, Pluto is known as one of the nine major planets in the solar system. However since 1992, astronomers began to doubt the status of Pluto as a planet after inspection like a planet. Finally, in August 2006, scientists officially announced that Pluto is no longer a planet. Suddenly, in the elementary school classroom, there is only one planet in these planet groups. Basic childhood books including Pluto are inaccurate. Pluto does not seem to meet the ideal of this "planet" by the astronomers of the International Astronomical Union.