Before forming embryos of planets, asteroids or comets, small objects go through many stages of construction.
Interplanetary space is not not really empty, it is littered with dust and gas from the creation of the solar system. Far from the nascent Sun, this debris from the protoplanet disc failed to regroup sufficiently to form a large, massive object, in hydrostatic equilibrium, ie spherical in shape.
However, the small blocks continue to grow more or less, but before becoming real objects compact, they are agglomerates made up of many small rocks the size of a pebble, the size of a boulder. All these objects form collections of various small objects, metallic and rocky, lightly stuck together by the force of gravity, all covered with dust and ice. The internal structure of these small objects looks like the image on the right.
All these little ones cosmic objects, are subject to the laws of celestial mechanics and their ballet around the Sun is chaotic by nature. The slightest disturbance is enough to upset their orbit and thus the dust and the small pebbles stick together by gravity.
Many researchers are interested in asteroids because they are the oldest vestiges of the creation of the solar system.
They did not undergo the effects of disintegration like the elements of larger bodies where radioactivity has modified the constituents of matter. These small debris of a few tens of meters formed the Sun, planets, moons, asteroids and comets. They come from the same primitive nebula of dust and gas. These objects are part of our system solar energy and have been revolving around it since its creation.
An asteroid is a celestial object, not observable with the naked eye because of its small size which varies from a few tens of meters to several hundreds of kilometers in diameter. Objects less than 50 meters in diameter are called meteorites. These are not satellites of planets but debris of the protoplanet disc which failed to regroup into planets during their formation.
The first asteroid was discovered by chance on December 31, 1800 by the Italian, Giuseppe Piazzi (1746 - 1826), director of the observatory from Palermo, Sicily.
It was while observing the constellation Taurus that he saw an unidentified object moving very slowly in the night sky. His colleague, Carl Friedrich Gauss (1777 - 1855) determined the exact distance of this unknown object and placed this star between the planets Mars and Jupiter.
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Image: X-ray of a small asteroid.
Small asteroids are not compact blocks but agglomerates made up of many small rocks the size of a pebble to the size of a house. The Asteroid Belt hosts a collection of diverse small asteroids that are lightly stuck together by the force of gravity. They are so weakly agglomerated that one could sink into them his point. The slightest shock would separate the debris.