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Oort Cloud Facts


The Oort cloud is a spherical cloud of icy objects. It is also known as the Opik-Oort Cloud. It surrounds the sun at approximately 50,000 AU. This extended shell exists in the outermost reaches of the solar system. It is thought to be the origin of most of the long-period comets that have been observed.

Astronomers believe that the particles of this cloud are remains of the disc material from which the Sun and other planets are formed. Halley’s Comet which is one of the best known comets is known to be originated in the Oort cloud.


Quick Facts: –

  • The cloud was theorized by astronomers Ernst Opik and Jan Oort.
  • The inner limit of the Oort cloud begins at about 2,000 AU from the Sun.
  • Objects that are found in this cloud are also known as Trans-Neptunian objects.
  • Nobody knows for sure how many objects are there in the cloud but an estimate is about 2 trillion.
  • These objects are mainly composed of water ice, methane and ammonia.
  • Astronomers believe that long-period comets that have orbital periods longer than 200 years originate in the Oort cloud.
  • This cloud is believed to be made up of two separate regions, a spherical Oort cloud and a disc-shaped inner cloud called Hills Cloud.
  • The dwarf planet Sedna is believed to be a part of the inner cloud. It orbits the sun once every 10,500 years.
  • The distance between the Sun and the cloud is immense and this is also the reason for the weak gravitational pull.
  • Although its existence is widely accepted we are yet to have a sighting of the Oort cloud.



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