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Facts about the Asteroid Belt For Kids


The asteroid belt is the region of the Solar System located roughly between the orbits of the planets Mars and Jupiter. It is occupied by numerous irregularly shaped bodies called asteroids or minor planets. The asteroid belt is also termed the main asteroid belt or main belt because there are other asteroids in the Solar System such as near-Earth asteroids and trojan asteroids.

  • About half the mass of the belt is contained in the four largest asteroids, Ceres, Vesta, Pallas, and Hygiea.
  • These have mean diameters of more than 400 km, while Ceres, the asteroid belt’s only dwarf planet, is about 950 km in diameter.
  • The asteroid material is so thinly distributed that numerous unmanned spacecraft have traversed it without incident.
  • Nonetheless, collisions between large asteroids do occur, and these can form an asteroid family whose members have similar orbital characteristics and compositions.
  • Collisions also produce a fine dust that forms a major component of the zodiacal light.
  • Between Mars and Jupiter, however, gravitational perturbations from the giant planet imbued the protoplanets with too much orbital energy for them to accrete into a planet.
  • Asteroid orbits continue to be appreciably perturbed whenever their period of revolution about the Sun forms an orbital resonance with Jupiter.
  • In an anonymous footnote to his 1766 translation of Charles Bonnet’s Contemplation de la Nature, the astronomer Johann Daniel Titius of Wittenberg noted an apparent pattern in the layout of the planets.
  • Modern asteroid survey systems now use automated means to locate new minor planets in ever-increasing quantities.
  • In general in the Solar System, planetary formation is thought to have occurred via a process comparable to the long-standing nebular hypothesis: a cloud of interstellar dust and gas collapsed under the influence of gravity to form a rotating disk of material that then further condensed to form the Sun and planets.
  • During the first few million years of the Solar System’s history, an accretion process of sticky collisions caused the clumping of small particles, which gradually increased in size.
  • Orbital resonances occurred where the orbital period of an object in the belt formed an integer fraction of the orbital period of Jupiter, perturbing the object into a different orbit; the region lying between the orbits of Mars and Jupiter contains many such orbital resonances.
  • Since their formation, the size distribution of the asteroid belt has remained relatively stable: there has been no significant increase or decrease in the typical dimensions of the main-belt asteroids.
  • The Hungaria asteroids lie closer to the Sun than the 4:1 resonance, but are protected from disruption by their high inclination.
  • Chemically, their spectra match the primordial composition of the early Solar System, with only the lighter elements and volatiles removed.
  • This hypothesis was reinforced by the further discovery in 2007 of two asteroids in the outer belt, 7472 Kumakiri and (10537) 1991 RY16, with differing basaltic composition that could not have originated from Vesta.
  • Kirkwood gaps The semi-major axis of an asteroid is used to describe the dimensions of its orbit around the Sun, and its value determines the minor planet’s orbital period.
  • An asteroid in the 3:1 Kirkwood gap would orbit the Sun three times for each Jovian orbit, for instance.
  • Due to the low density of materials within the belt, the odds of a probe running into an asteroid are now estimated at less than one in a billion.