The Asteroid Belt

The Asteroid Belt

The asteroid belt is a region where mostly small solid, irregularly shaped rocky, and metallic bodies, orbit the Sun; these small bodies are sometimes referred as minor planets.

The Asteroid belt is located in between Mars and Jupiter. The asteroid belt between Mars and Jupiter is also called the main belt, or main asteroid belt in order to distinguish it from other belts, across the solar system.

The main belt a torus-shape (doughnut) located about 329-478 million km away.

The total mass of the main belt is approximately 4% of the Earths Moon mass.

About half of the main belts mass is made up by four large asteroids Ceres, Vesta, Pallas and Hygiea. Of the four asteroids, Ceres is the largest.

Ceres has a diameter of 950 km or 590 miles (Ceres is large enough to be a dwarf planet).  Vesta, Pallas and Hygiea have diameters less than 600km or 373 miles.

The Asteroid Belt


The solar system started as a large cloud of dust and ice. However, explosion of a nearby star disrupted the mass and resulted in the gas and dust spinning and increasing in speed and gravity began to clump together bodies together called planetesimals. These planetesimals turned into proto-planets and then formed planets.

In order for planet to form there has to be just enough gravity. Too much or too little and planets, stars, moons, and galaxies will not form.

The area between Jupiter and Mars did not have enough gravity. Jupiter is the largest planet in our solar system. Thus Jupiter’s strong gravitational pull prevented any objects from forming in the main belt.

Jupiter’s gravitational pull prevents anything large from being formed in the main belt because it would be ripped apart into smaller bits.


In 1596, Johannes Kepler hypothesized there might be a planet between Mars and Jupiter. He wrote “ I place a planet” in his Mysterium Cosmographicum. Johannes Kepler placed a planet between Mars and Jupiter because he believed the space was too large.

The first object in the main belt was discovered in 1800 with a group of 25 astronomers was formed called the celestial police. Each member searched 15° of the zodiac for a missing planet. However, the first body was not discovered by a member. Italian astronomer  to find an object in the asteroid belt. He discovered and named Ceres. Pallas was found a year later. For some time astronomers believed they found the missing planets. But the discovery rate increased, in the 19th century. Astronomers realized the planets were too small and began naming the once small planets asteroids.

The Asteroid Belt

Image Credit


giuseppe piazzi

asteroid belt



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