The asteroids they are a series of rocky or metallic objects that orbit the Sun, mostly in the main belt, located between Mars and Jupiter.
Some asteroids, however, have orbits that go beyond Saturn, others are closer to the Sun than Earth.
Some have crashed into our planet. When they enter the atmosphere, they light up and become meteorites.
The larger asteroids are also sometimes called minor planets. Some have partners. The largest asteroid is Ceres, with almost 1,000 km in diameter. In 2006 the International Astronomical Union (UAI) defined it as dwarf planet, like Pluto. Then come Vesta and Pallas, with 525 km. 16 have been found that exceed 240 km, and many small. Gaspra, the one pictured above, does not reach 35 km from end to end, while Ida (below, with its satellite) is about 115 km.
The total mass of all asteroids in the Solar System is much smaller than that of the Moon. The largest bodies are more or less spherical, but those with diameters smaller than 160 km have elongated and irregular shapes. Most take 5 to 20 hours to complete a turn on its axis. The table shows the data of some asteroids:
|Asteroid||Radio||Average distance to the Sun||Discovered in|
|Ceres||457 km||413,900,000 km.||1801|
|Pallas||261 km||414,500,000 km.||1802|
|Vesta||262 km||353,400,000 km.||1807|
|Hygiea||215 km||470,300,000 km.||1849|
|Eunomia||136 km.||395,500,000 km.||1851|
|Psyche||132 km||437,100,000 km.||1852|
|Europe||156 km||436,300,000 km.||1858|
|Silvia||136 km.||512,500,000 km.||1866|
|Going||58 x 23 km.||270,000,000 km.||1884|
|Gives life||168 km.||475,400,000 km.||1903|
|Interamnia||167 km.||458,100,000 km.||1910|
|Gaspra||17 x 10 km.||205,000,000 km.||1916|
Few scientists believe that asteroids are the remains of a planet that was destroyed. Most likely, they occupy the place in the Solar System where a planet of considerable size could have formed, which did not occur because of Jupiter's disruptive influences.
Larger asteroids usually have impact masks produced by smaller ones; In the image below a crater is shown on the surface of Ceres. It is believed that most of the meteorites recovered on Earth are asteroid fragments. Like meteorites, asteroids can be classified into several types:
Three quarters of the asteroids visible from Earth, including Ceres, they belong to type C, and seem to be related to a class of meteorites called carbonaceous condritos, which are formed by the oldest materials of the Solar System, with a composition that reflects that of the primitive solar nebulae.
The asteroids of types, related to stony-ferrous meteorites, constitute approximately 15% of the total.
Much more rare are the objects of type M, which correspond to ferrous meteorites by their composition. They are composed of an alloy of iron and nickel. They represent the nuclei of the planetary bodies to which the subsequent impacts stripped of their outer layers.
A few asteroids, including Vesta, perhaps they are related to the strangest class of meteorites: achondrites. They seem to have on their surface a composition similar to terrestrial lava. Therefore, astronomers are reasonably certain that Vesta, at some point in its history, partially softened.
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