Key Facts about Comet

About Comet:

• Comets are large objects made of dust and ice that orbit the Sun.
• Best known for their long, streaming tails, these ancient objects are leftovers from the formation of the solar system 6 billion years ago.
• Comets are mostly found way out in the solar system.
• Some exist in a wide disk beyond the orbit of Neptune called the Kuiper Belt.
  • We call these short-period comets. They take less than 200 years to orbit the Sun.
• Other comets live in the Oort Cloud, the sphere-shaped, outer edge of the solar system that is about 50 times farther away from the Sun than the Kuiper Belt.
  • These are called long-period comets because they take much longer to orbit the Sun.
• The comet with the longest known orbit takes more than 250,000 years to make just one trip around the Sun.
• A comet is made up of four visible parts: the nucleus, the coma, the ion tail, and the dust tail.
  • The nucleus is a solid body typically a few kilometres in diameter and made up of a mixture of volatile ices (predominantly water ice) and silicate and organic dust
  • The coma is the freely escaping atmosphere around the nucleus that forms when the comet comes close to the Sun and the volatile ices sublimate, carrying with them dust particles that are intimately mixed with the frozen ices in the nucleus.
  • The dust tail forms from those dust particles and is blown back by solar radiation pressure to form a long curving tail that is typically white or yellow in colour.
  • The ion tail forms from the volatile gases in the coma when they are ionized by ultraviolet photons from the Sun and blown away by the solar wind.
  • Ion tails point almost exactly away from the Sun and glow bluish in colour because of the presence of CO^+.