Asteroids were first discovered because they broke Bode's Law that dealt with the distance of a heavenly body from the sun (although the law was later disproved). Scientist noted that the distance from Mars to Jupiter was too large and theorized that another planet had to lie between them.

On the first of January in 1801, Giuseppe Piazzi discovered Ceres, the largest asteroid in the asteroid belt. It is 620 miles in diameter and makes up a quarter (25%) of the total combined mass of all the other asteroids.

There are twenty-six known asteroids in the asteroid belt. Most are greater than 0.9 miles in diameter. The combined mass of all the asteroids is even less than the mass of our Moon!!

Although scientist don't know exactly how asteroids formed, they do have several theories. One is that they may be material that never formed into a planet. Another is that perhaps a planet got too close to Jupiter and the gravity of Jupiter broke it up.

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