Comets are small celestial bodies composed of ice, dust, and rocky material that orbit the Sun in highly elliptical paths. When a comet approaches the Sun, the heat causes the comet’s ices to sublimate, creating a glowing coma (a cloud of gas and dust) and sometimes a tail. Comets provide valuable information about the early solar system because they are relatively unchanged remnants from its formation. Comets also have a rich history of cultural and historical significance due to their dramatic appearances in the night sky.

• • Nucleus: The solid core of a comet, made up of a mixture of water ice, frozen gases, and rock. It is typically a few kilometres in diameter.
  • Coma: A glowing cloud of gas and dust that forms around the nucleus when the comet is close to the Sun. The coma can be much larger than the nucleus.
  • Tail: The tail of a comet forms as solar radiation heats the coma, causing particles and gases to be pushed away from the comet by the solar wind. There are usually two tails, a dust tail, which is broad and curved, and an ion (or gas) tail, which is straight and points away from the Sun.
  • Orbit: Comets have highly elliptical orbits that take them from the outer regions of the solar system, such as the Kuiper Belt or Oort Cloud, to the inner solar system and back. Their orbits can be very long, ranging from decades to thousands of years.
  • Short-Period Comets: These comets have orbits that bring them close to the Sun at regular intervals, typically less than 200 years. They are thought to originate from the Kuiper Belt.
  • Long-Period Comets: These have orbits that take them much farther from the Sun, with periods ranging from several hundred to thousands of years. They are believed to come from the Oort Cloud.
    
    

Notable Comets

• • Halley’s Comet: One of the most famous comets, visible from Earth approximately every 76 years. It was observed by astronomers such as Edmund Halley, who predicted its return.
  • Hale-Bopp: A bright comet observed in 1996 and 1997, notable for its long visibility and bright appearance.
  • Comet Hyakutake: A bright comet that passed close to Earth in 1996, also known for its impressive tail.