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Asteroid Eros
http://veimages.gsfc.nasa.gov/10824/eros_still_edge_true_0007_web.jpg
Asteroids are rocky and metallic bodies, which orbit around the Sun or go with orbital movement of planets in a few specific points. They are small to be called planets, so therefore are called planetoids or minor planets.
The Asteroid Belt is the region of the Solar System, located between the orbits of Mars and Jupiter, which contains a large number of asteroids. Their sizes are varied, but only 26 of them have hundreds of kilometers of diameter. The vast majority are small.
Their orbits are located between 2 to 4 AU from the Sun. They are elliptical and complete one lap around the Sun every 3 to 6 years. Due to the gravitational action of Jupiter there are some regions that do not have the belt asteroids. These failures were discovered by Daniel Kirkwood (1814-1895) in 1866.
We still know very few about the population of asteroids. The last survey, done in infrared by the ISO (Infrared Space Observatory and European Space Agency (ESA) showed that there may have between 1.1 and 1.9 million asteroids with a diameter of 1km. And smaller bodies may reach millions and even billions in number.
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