Why are Asteroids not called Planets?
338718
The definition of a planet is rather ambiguous.  Broadly, it is a body of matter orbiting a star which is not large enough to produce nuclear fusion (that would make it a star).  Additionally, planets must be significantly larger than any objects in a similar orbit.\nThis obviously excludes asteroids, however it is a contested definition since it also excludes Kuiper Belt objects, including Pluto and Ceres.\nAnother clause suggested is that the body must be large enough that its gravity causes it to form a roughly spherical shape, which most asteroids do not.\nThere are other suggested definitions, see http://en.wikipedia.org/wiki/Planet
777012
i suppose a planet.cause it is denser then asteroids
415678
The name of our planet is the Earth. The name of our moon is the Moon. The name of our solar system is the Solar System. \n\nNotice that I capitalize them, because when used as names, they are proper nouns. This also helps us distinguish between the planet Earth and earth (meaning soil), between the Earth's Moon and moon (meaning the natural satellite of a planet), and between our Solar System and any other solar systems (since any system containing a star and a planet or a planet-forming disk can be called a solar system.) \n\nThis is the usage approved by the International Astronomical Union, the body in charge of naming celestial objects. It may seem odd that these important objects don't have names, but if you think about it, it just reinforces their importance. For example, the Moon is the Moon, not just any moon. It requires no other name, because it's the most important moon! \n\nYou may read or hear people using Luna for the Moon, or Terra or Gaia for the Earth, or Sol for the Sun, but these are poetic terms, often seen in science fiction stories, but not used by astronomers in scientific writing.
1164830
Oh Boy! got it right. The larger asteroids are also basically spherical. This is ultimately due to the fact that they have enough mass for the gravity to force them into this shape. Of course, there are irregularities, but they are fairly small except for the bulges caused by rotation. The smaller asteroids don't have enough mass for the gravity to have much effect.
1050595
There are three types of asteroid bodies.\n\nStony:  Mostly silicates and the lighter metals that compose most of the crust of the Earth (sand)\n\nNickle Iron: Mostly Heavy Iron and Nickle, but also gold, silver, and radioactive metals, the stuff found in the Earth's core.\n\nCarbonaceous Corondite: This is mostly carbon and ice, cometary you might say... \n\nOur moon is made up of the lighter material because it was formed by a collision with another planet that tore a huge amount of crust material off which formed into the moon.  \n\nThe reason for separation of the materials into layers should be obvious but it is because when formed the liquids settle out by weight, heaviest sinks lowest displacing the rest.
112912
Gravity pulls everything to the center. The larger the object the greater the gravity the more perfect a sphere. Jupiter has a smoother surface than the earth. The earth is smoother than the moon. Asteroids are even smaller and don't always have enough gravity to overcome the structural properties of the mineral it is made of, so smaller asteroids have more unusual shapes and are not always very spherical.
892153
Today kids are not taught that Ceres was once a planet, before it got downgraded to the newly created category of asteroid in about 1850. So I suspect that in 100 years the whole Pluto thing will be forgotten in the same way.
552556
It is certainly possible that some of the many tiny moons of the larger, gas giant, planets could have come from the asteroid belt.  Those massive planets' gravitational field are prone to capture a lot of debris from the solar system.\n\nWow, FishRN, it must have taken a lot out of you to copy paste that whole thing from the wikipedia article, so much so that you couldnt even list your source.\nhttp://en.wikipedia.org/wiki/Asteroid_belt
1183831
THere is an argument among astromoners as to whether classify the bodies beyond pluto as planets... consider that in the asteroid belt there are many objects orbiting the sun... do we call them all planets?\n\nCurrently there are officially only 9 planets:\nMercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto.
669912
An asteroid is a small, solid object in our Solar System, orbiting the Sun. An asteroid is an example of a minor planet (or planetoid). These minor planets are much less massive than even small planets such as Mercury or Mars. It is believed that most asteroids are remnants of the protoplanetary disc. The incorporation of these remnants into the planets during the formation of the Solar System was prevented by large gravitational perturbations induced by Jupiter. Some asteroids have moons. The vast majority of the asteroids are within the main asteroid belt, with elliptical orbits between those of Mars and Jupiter.
104242
Yes! The 10th planet was discovered in 2005, and is temporarily known as 2003 UB313.  However, 2003 UB313 is located in the Kuiper belt, which is made up of numerous objects, and there may be many more that could be counted as planets.  The definition of "planet" is currently a topic of debate, and some argue that neither 2003 UB313 nor Pluto should be considered planets.  I believe that the popular media has sometimes refered to it as "planet x," but this is not its official name.
760765
well, technically the last celestial body to be officially classified as a planet at the time was Pluto, but since it's demotion I'm not sure you can say that any more, so it's going to be Neptune in that case.
109946
There is only one solar system, and it is the one our planet is part of.\n\nThe solar system comprises the Earth's Sun and the retinue of celestial objects gravitationally bound to it. Traditionally, this is said to consist of the Sun, nine planets and their 158 currently known moons; however, a large number of other objects, including asteroids, meteoroids, planetoids, comets, and interplanetary dust, orbit the Sun as well. Astornomers are debating over the presence of a tenth planet.\n\nAlthough the term "solar system" is frequently applied to other star systems and the planetary systems which may comprise them, it should strictly refer to Earth's system specifically: the word "solar" is derived from the Sun's Latin name, Sol, and thus the term sometimes appears as Solar System. When talking about another stellar system or planetary system, including the stars and bodies associated with them through gravity, it is usual to shorten it to drop the term "stellar" and form names such as "the Alpha Centauri system" or "the 51 Pegasi system".
945846
This issue is very similar to the asteroid belt issue some 150 years ago.  When the first asteroid, Ceres, was found, it was considered a planet.  Only after 15 other "planets" were found in the same orbit regime did astronomers downgrade these asteroids to "minor planets" some 50 years after Ceres' discovery.\n\nIt's unclear if Pluto could ever clear its orbit...it crrently has only 7% of the mass of its orbital neighborhood (as opposed to, say, Earth, which contains some 99.9999% the mass of its orbital neighborhood), so it's only cleared a tiny fraction of its orbit throughout the entire age of the Solar System, 4.5 billion years.\n\nMoreover, other objects in Pluto's orbit (and pluto itself, in fact) are trapped in a 3:2 orbital resonance with Neptune.  This means these "plutinos" are in a very stable orbit, unlikely to be scattered away unless something very big and unexpected comes along.
227911
The inner planets are the 4 planets who's orbits are closest to the sun (Mercury, Venus, Earth, and Mars).  The asteroid belt (and millions and millions of miles) seperates the inner planets from the outer planets.\n\nCompared to the distances in between the outer planets, the inner planets might as well be right next to eachother, the distances really start getting big in the outer solar system.
1170805
Well that is a very good question, and one that is being debated as we speak. We now know that Pluto is much smaller than we previously thought (it is a very small planet and a moon) And we have now discovered a very large asteroid that some people want to call planet 10. In fact some people want to reclassify Pluto as they think it is too small to be called a planet.\n\nThe problem is that there is really no "exact" definition of what a planet is. I mean obviously a large body that orbits a star, is part of the definition. but when you get to smaller objects in irregular orbits, are they planets? planetoids? asteroids? something else?\nSo as for how large does an object have to be?\nwe will have to wait for the IAU (International Astronomical Union)\nto come up with a rigidly defined definition.\n\npersonally, I say an object that has enough mass to cause gravity to shape it into a sphere and has its own atmosphere should be called a planet. But hey that is just my personal opinion.\ncheck out these articles.\n\nhttp://news.bbc.co.uk/2/hi/science/nature/259767.stm\n\nhttp://www.space.com/scienceastronomy/planet_denitions_030227.html
800316
http://en.wikipedia.org/wiki/Pluto\n\non 24 august 2006, the international astronomical union reclassified pluto.\n\npluto 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.\n\ni 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 enuf. i can accept that the definition is flawed, but i can not accept that "134340 pluto" is a planet.\n\nthis 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.\n\nthis 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.\n\nmany astronomers consider pluto and charon to be a binary system, but two small bodies orbit that system. they are called nix and hydra.\n\nincidentally, "134340 pluto" was never a moon of neptune. neptune did capture triton. this is why triton has a retrograde orbit