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A comet is an icy small Solar System body (SSSB) that, when close enough to the Sun, displays a visible coma (a thin, fuzzy, temporary atmosphere) and sometimes also a tail. These phenomena are both due to the effects of solar radiation and the solar wind upon the nucleus of the comet. Comet nuclei range from a few hundred meters to tens of kilometers across and are composed of loose collections of ice, dust and small rocky particles. Comets have been observed since ancient times.
Comets have a wide range of orbital periods, ranging from a few years to hundreds of thousands of years. Short-period comets originate in the Kuiper belt, or its associated scattered disc,[1] which lie beyond the orbit of Neptune. Longer-period comets are thought to originate in the Oort cloud, a hypothesized spherical cloud of icy bodies in the outer Solar System. Long-period comets plunge towards the Sun from the Oort cloud because of gravitational perturbations caused by either the massive outer planets of the Solar System (Jupiter, Saturn, Uranus, and Neptune), or passing stars. Rare hyperbolic comets pass once through the inner Solar System before being thrown out into interstellar space along hyperbolic trajectories. Exocomets, comets beyond our solar system, have also been detected and may be common in the Milky Way Galaxy.[2]
Comets are distinguished from asteroids by the presence of a coma or a tail. However, extinct comets that have passed close to the Sun many times have lost nearly all of their volatile ices and dust and may come to resemble small asteroids.[3] Asteroids are thought to have a different origin from comets, having formed inside the orbit of Jupiter rather than in the outer Solar System.[4][5] The discovery of main-belt comets and active centaurs has blurred the distinction between asteroids and comets (see asteroid terminology).
As of January 2011 there are a reported 4,185 known comets[6] of which about 1,500 are Kreutz Sungrazers and about 484 are short-period.[7] This number is steadily increasing. However, this represents only a tiny fraction of the total potential comet population: the reservoir of comet-like bodies in the outer Solar System may number one trillion.[8] The number visible to the naked eye averages roughly one per year, though many of these are faint and unspectacular.[9] Particularly bright or notable examples are called "Great Comets".

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  1. 1. COMETSPrepared By:- Kishan V
  2. 2. WHAT ARE COMETS?ar From Pluto There is a group of aboutmillions of celestials objects. It is knowas cloud of Oort or Kuiper-belt . Theseobjects due to some reasons start movingtowards the sun. They are known ascomets. Comet are made up of dust andicy rocks.
  3. 3. COMET TAILhen the comet starts moving towardsthe sun the ice which is frozen aroundthe nucleus of the comet starts melting.When the comet is near to the sun thetail of it is longest and when it startsmoving far from the sun the tail becomesshorter And last it vanishes.
  4. 4. TWO TYPES OF TAILS Ion tail: Ionized gas pushed away from the comet by the solar wind. Pointing straight away from the sun.Dust tail: Dust set free fromvaporizing ice in the comet;carried away from the cometby the sun’s radiationpressure. Lagging behind thecomet along its trajectory
  5. 5. TAILED-STARf we see from the earth we see the tail isseen with the comet so it is know as aTailed-star.n fact it is not a star and its tail is notpermanent.
  6. 6. HALLEY’S COMETar from orbits of more than750 cometsare know.he most famous comet is Halley’s comet.t visits our solar family every 76 years.t was last seen in 1996.
  7. 7. EDMOND HALLEY  In 1704 Sir Edmond Halley found that that comet and it was named after Halley.  In 1704 Sir Edmond Halley hypothesized that the comets of 1456, 1532, 1607, 1682 were the same object. He calculated a 75.7 year orbit and predicted that it would return in 1758. Halley died; but comet returned.
  9. 9. COMPOSITION OF COMETces• H2O, Carbon Monoxide (CO), Methanol(CH3OH), and other frozen materials Minerals • Silicate mineralsomplex organic molecules and dust particles• C=Carbon• H=Hydrogen• O=Oxygen• N=Nitrogen
  10. 10. COMET AS BAD LUCK IN OLD AGEIn ancient days arrival of the comet wasconsidered to be responsiblefor war, epidemicor a natural calamity like flood.But mordern science has proved that arrivaland departure of a comet is just a normal eventand there is no need to panic about it.
  11. 11. THANK YOU