Comets & Small-Body Reservoirs

Explore by theme

• All Comets

  Every comet and transition object modelled in the encyclopedia.

  21 entries
• Periodic Comets

  Comets that return on measured orbits, from Encke's 3.3 years to Halley's 76.

  13 entries
• Long-Period Comets

  Comets on orbits longer than ~200 years, arriving from the Oort cloud.

  6 entries
• Great Comets

  The rare, brilliant comets that become naked-eye spectacles — Hale–Bopp, NEOWISE, McNaught, and more.

  5 entries
• Jupiter-Family Comets

  Short-period comets shepherded by Jupiter, originating in the scattered disc.

  10 entries
• Halley-Type Comets

  Periodic comets with intermediate orbits of decades to two centuries.

  3 entries
• Sungrazing Comets

  Comets that skim the Sun at perihelion, most of them members of the Kreutz family.

  2 entries
• Main-Belt Comets

  Bodies on asteroid-belt orbits that display recurring comet-like activity.

  1 entries
• Oort Cloud Comets

  Comets whose source is the distant, spherical Oort cloud.

  9 entries
• Scattered-Disc Comets

  Jupiter-family comets sourced from the scattered disc beyond Neptune (reusing Program Y's population).

  9 entries
• Meteor-Shower Parent Bodies

  The comets and asteroids whose debris streams produce the annual meteor showers.

  8 entries
• Comet Missions

  Comets and transition objects that have been visited by a spacecraft.

  7 entries
• Sample-Return Comets

  Comets from which spacecraft have returned material to Earth.

  1 entries
• Planetary-Defense Comets

  Comets relevant to impact studies — the Jupiter impactor Shoemaker–Levy 9 and the Mars close-approacher Siding Spring.

  3 entries
• Historic Comets

  The great and periodic comets discovered before the twentieth century.

  8 entries
• Transition Objects

  Objects that blur the line between asteroid and comet — active asteroids and dormant comets.

  4 entries
• Active Asteroids

  Asteroids that show comet-like activity, such as the Geminids parent Phaethon.

  2 entries
• Dormant Comets

  Extinct or dormant cometary nuclei on comet-like orbits.

  2 entries

Comet classes

• Jupiter-Family Comets
  10 modelled
• Halley-Type Comets
  3 modelled
• Long-Period Comets
  6 modelled
• Sungrazing Comets
  2 modelled
• Main-Belt Comets
  1 modelled

Source reservoirs

Where comets come from — the two Oort-cloud regions modelled here, plus Program Y's trans-Neptunian populations, reused.

• Oort Cloud
  ≈ 2,000–100,000 AU
• Inner Oort Cloud
  ≈ 2,000–20,000 AU
• Kuiper Belt
  Reused from the asteroid encyclopedia
• Scattered Disc
  Reused from the asteroid encyclopedia
• Centaurs
  Reused from the asteroid encyclopedia

Comet families & transition objects

• Kreutz Sungrazers
  Genetic family
• Active asteroids
  2 modelled
• Dormant comets
  2 modelled