Comet, Asteroid & Meteor (CAM) Section

Section Director: Tim Cooper
Activity areas: Comets, Asteroids, Meteors
Publications: CAMnotes, Comet Observing GuideMeteor Observing Guide (PDF)
Specialists & Collaborators: Kos Coronaios
Contact us: [ ]



Comets, asteroids and meteors may be considered as the debris of the solar system.  They are members of the group of objects known as Small Solar System Bodies, which are any solar system body too small to meet the definition of either a planet or dwarf planet.  The CAM Section is involved in the observation of these bodies, which are important to our understanding of the formation and evolution of our solar system.

Definition of terms

The following definitions are from those accepted by the IAU.

  • An asteroid, also known as a minor planet, is an irregularly shaped rocky body orbiting the Sun that does not meet the definition of either a planet or dwarf planet.
  • A comet is a small body orbiting the Sun, and comprising a substantial fraction of its composition as volatile matter, which can sublimate under the effect of solar radiation to form a coma.
  • A meteoroid is a solid natural object of a size roughly between 30 µm and 1m moving in, or coming from, interplanetary space.
  • A meteor is the light and associated physical phenomena (heat, shock, ionization), which result from the high speed entry of a solid object from space into a gaseous atmosphere. A meteor brighter than visual magnitude –4 is termed a bolide or a fireball.
  • A meteorite – is any natural solid object that survived the meteor phase in a gaseous atmosphere without being completely vaporized.
  • A meteor shower is a group of meteors produced by meteoroids of the same meteoroid stream, and may be formed by either a comet or asteroid.

What observations can be made?

  • Comets: for observations to be of scientific value the observer should concentrate on making estimates of the total visual magnitude of the comet (preferably made over the entire apparition to allow construction of a light curve), the diameter of the coma, the degree of condensation of the comet, and the length and position angle of the tail. Detailed visual descriptions, sketches and photographs of the comet should also be recorded. Further details are given in our Guide to Observing Comets.
  • Asteroids: determination of size and shape by timing occultations of stars by asteroids, light curve studies to determine rotation rates.
  • Meteors: visual counts in order to determine time of maxima and generate activity profiles of showers, recording of shower meteor magnitudes to determine population index, and plotting of meteors to determine radiant position and structure. In addition, the Section participates in global video monitoring networks, in order to detect new meteor streams and confirm showers listed by the IAU Meteor Data Centre (MDC). Find out more on the About Meteors page.
  • Fireballs: any meteor of magnitude –4 or brighter is of great interest and should be reported! Please use the Report a Sighting page to share your sighting.

Comet compendium

Meteor compendium