Pluto was reclassified as a "dwarf planet" because it does not dominate the neighborhood around its orbit. Pluto's "moon," Charon is about half its size. True planets are much larger than their moons.
Now anyone to make a good clarification to me why pluto is not considered as a planet.
Mimi niliambiwa it is because Pluto has not its origins in our solar system. From the big bang all our planet and the sun came from the same "thing" but PLuto came as an asteroid from another system and got stuck around the sun because of its low mass. Sasa walivo discover pluto walidhani ni kubwa kama march na wakasema kuna "miezi" zinazunguuka pluto. However with recent technology wamegundua kuna "miezi" ya pluton zilizo kubwa kuliko pluton yenyewe na zinazo miezi yao wenyewe. (SIjui naeleweka hapa?). BAsi wakaamua waache neno planet because inazunguuka jua ila wakasema ni "dwarf" planet sababu nikadogo mno ukilinganisha na planets zingine.
Wikipedia wanasema: Although Pluto was discovered in 1930 , was the first photographed 19 March 1915 . When Pluto was discovered, astronomers thought at first that it was about as large as in March . Moreover, they knew not to other, larger planets in the parts of the solar system beyond the giant planets, only comets , which are much smaller.
Better observations showed later that Pluto was smaller than expected, and in the 1990s, it was discovered many celestial objects in the same orbit as Pluto. Some of these were comparable to Pluto in size, prompting some astronomers to question whether it was appropriate to count Pluto as a planet, or whether it should recategorize to such an asteroid . (Something similar happened in the 1800s , when the discovery of the asteroid belt resulted in Ceres , Pallas , Juno and Vesta , which had previously been categorized as a planet number 5, 6, 7 and 8, was to recategorize asteroids and planetoids .)
The discovery of Eris , which orbits beyond Pluto and is larger diameter, further underlined the need to redefine the concepts of planetary and solar system. The question was debated at the International Astronomical Union's congress in Prague in August 2006 , and the result was that Pluto was redefined as a dwarf planet and is the prototype of a sub-category of this type of celestial bodies. This subcategory was in June 2008 titled "plutoider." The term "plutons" was first proposed, but rejected after protests by geologists, as this is the international term for what is usually called in Norwegian rocks .
