Asteroid Belt

Asteroid Belt, also known as Main Asteroid Belt and Main Belt. In the image above we have Main Belt’s map, even though it might not look like much of a map, but it’s in fact is map of the Asteroid Belt. The x-axis are named as Semimajor axis (AU), is the distance of the family from Sun in AU units (meaning: one AU unit is an average distance of Earth to Sun).

Largest bodies

Ceres, Vesta, Pallas, Hygiea comprises about half of the total mass of Main Asteroid Belt. Ceres is classified as Dwarf planet, being largest object in Main Belt. In the Asteroid Belt there is over 200 bodies bigger then 100 km and about 1.7 million bodies bigger then 1 km in diameter. Even having such a big number of objects of different size in Asteroid Belt it would be next to impossible to hit any of them without precise aim.

Kirkwood Gap

It is named after Daniel Kirkwood who noticed these gaps in 1866 and was also who explained the origin of them correctly, the origin was the orbital resonances with Jupiter while being a professor at Jefferson College in Canonsburg, Pennsylvania.

Some of the most prominent Kirkwood Gaps:

  • 4:1 resonance at 2.06 AU
  • 3:1 resonance at 2.5 AU
  • 5:2 resonance at 2.82 AU
  • 7:3 resonance at 2.95 AU
  • 2:1 resonance at 3.27 AU

And some of the weaker Kirkwood Gaps:

  • 9:2 resonance at 1.9 AU
  • 7:2 resonance at 2.25 AU
  • 10:3 resonance at 2.33 AU
  • 8:3 resonance at 2.71 AU
  • 9:4 resonance at 3.03 AU
  • 11:5 resonance at 3.075 AU
  • 11:6 resonance at 3.46 AU
  • 5:3 resonance at 3.7 AU


Families and groups

Observation of Asteroid Belt was never easy, the fact that it contains so many small objects its extremely difficult to categorise all of them. The lack of smaller object observation raised another problem,connection between meteorites and asteroids. Small Main-belt Asteroid Spectroscopic Survey (SMASS) aimed to resolve this problem. After finishing SMASS survey distinctive groups and families arrived:

  • Zone 1 – Pallas family
  • Zone 2 – Astrid family
  • Zone 3 – Chloris family
  • Zone 4 – Dora and Phaeo families
  • Zone 5 – Gefion family
  • Zone 6 – Agnia, Henan, Hoffmeister, Lydia families
  • Zone 7 – Merxia, Thisbe families
  • Zone 8 – Menippe, Watsonia, Weringia families

After removing primary family members what left was just background objects, 272 of them. From all background objects just four most prominent groupings where marked.

  • Bellona
  • Coelestina
  • Eugenia
  • Liberatrix

All of these families are group of spectral families containing 19 members, and all this information bin published in 1999’s by Massachusetts Institute of Technology.


Reference list:

NASA gallery

NASA’s Down Mission belt

MIT Libraries

Oxford Academy