On 1 January 1801 , Giuseppe Piazzi discovered a celestial body orbiting in an orbit between Mars and Jupiter. According to the empirical law of Titus- Bode, there had to be a planet there : was it this new planet ? In fact, its small size does not fit with this hypothesis : Piazzi had discovered the first asteroid he named Ceres. Soon, we discovered many others.
We know today (November 11, 2014) 664 036 asteroids of which 415 688 numbered (whose orbit is sure), ranging in size from a few tens of meters to hundreds of kilometers. Among these objects, 18 977 have been named .
These objects are visible from Earth only as small bright points without apparent diameter similar to the stars. Only their motion shows their presence. They are also called "minor planets".