Comet is a celestial body that moves around the Sun in highly elliptical orbits and develops a long, bright tail when it passes near the sun. It is made up of ices, carbon dioxide, ammonia, methane all mixed with dust. Comets have a nucleus and a coma. Nucleus is the icy center and coma is the cloud of gas and dust that surrounds the nucleus. When the ice in the nucleus is heated up by the Sun and vaporizes it forms coma. Two tails a straight gas tail and a curved dust tail are formed in Comets as they approach the sun.
A Comet physically consists of a head and tail. Nucleus lies at the center of the Comet’s head. Surrounding the nucleus is the diffused, bright region called the coma. The nucleus is made up of ice and traces of dust and is also called the “Dirty Snowball”. When this nucleus is heated up by the Sun the ice in the nucleus starts melting and then vaporizes forming a gaseous envelope surrounding the nucleus known as coma. It is bright due to sunlight’s reflection and also due to the emission of electromagnetic radiation.
The tail of a Comet is very long and bright. It is usually of two type’s straight gas tail also called ion tail and curved dust tail. The straight gas tail is formed when the ultraviolet sunlight carries out ionization by releasing one or more electrons from the nucleus of the coma. Immediately the solar wind carries these ions straight outwards from the Sun making the comet look straighter and narrower. Dust tail is composed of small, solid dust particles and is formed from the pressure of the light from the Sun. As the pressure applied is very weak the dust particles diffuses and forms a curved tail. Once the Comet moves away from the Sun its tail dissolute, coma disappears and the matter present inside the nucleus freezes like a rock.
Comets are named after their discoverer. If the comet is a periodic comet then it is denoted by P/ followed by the year of discovery and a letter indicating the half-month in which it was discovered and lastly followed by a number indicating its order of discovery. Similarly, a non-periodic comet is denoted by C/ followed by the year of discovery and a letter indicating the half-month in which it was discovered and lastly followed by a number indicating its order of discovery. Ten mostly known comets are as follows:
||Name of Comet
||Year of Discovery
||Name of Discoverer
|| Comet Lovejoy
|| Terry Lovejoy
|| Very bright and even visible in the daytime
|| Comets Hale-Bopp & Hyakutake
|| Alan Hale & Thomas Bopp
|| Intrinsically large and bright
|| Eclipse Comet
|| Bright comet present near the Sun
|| Great March Comet
|| Very big fan-shaped tail having a length of 2 astronomical units
|| Great Comet
|| Isaac Newton used the comet’s orbit as a study in the verification of Kepler’s laws of motion
|| Halley’s Comet
|| Sir Edmond Halley
|| Halley’s Comet visits the inner solar system every 75-76 years
|| Great September Comet
|| Produces bright anti-tail, sharp, spikey looking feature pointing sunwards
|| Great January Comet
|| South African diamond miners
|| Lexell’s Comet
|| It contains coma which is four times the full Moon size
|| Comet McNaught
|| McNaught is revolving on an extremely long period orbit, that won’t return to the inner solar system for another 92,600 years
Few of the interesting and valid facts about Comets are as follows:
a) The nucleus of the Comet is made up of ice and its size varies from a few meters to thousand kilometers.
b) Perihelion is sad t be the closest point on the Comet’s orbit from the Sun and Aphelion is the farthest point on the Comet’s orbit from the Sun.
c) When the Comet moves closer and closer to the Sun, due to the heat of the Sun the dry ice sublimates forming vaporization of the ice like seen in mini geysers.
d) Particles from the Comets streams out and enters other planet’s orbit if it enters that path. The it’s said to form “Meteor Showers”.
e) When the Comet comes too close to the Sun, it keeps n losing its weight due to sublimation. If it comes very close to the sun then, the Comet might break up.
f) Comets are made up ice, methane, ammonia, carbon dioxide mixed with rock and dust particles.
g) Comets usually consist of two tails – curved dust tail and straight gas tail also known as ion tail. Dust tail can be visible through naked eyes but gas tail or ion tail is not visible through naked eyes.
h) The orbits on which the Comets revolve are usually elliptical in shape.
i) Good number of Comets are formed in the outermost region of the solar system called the Oort cloud and the Kuiper belts.
j) Comets are also known as “Dirty snowballs” or “ Cosmic snowballs” as it is mainly composed of ice, rock, gas, and dust.
• Comet Encke (2P/Encke) (March 10th, 2017) is the quickest known orbit of any comet
• Comet Wirtanen (December 12th, 2018) one of the comets to pass closest to Earth between 2000 and 2200 CE
• Comet 209P / LINEAR (June 12, 2019)
• Comet Neujmin 2 (Aug 17, 2019)
• Comet 289P / Blanpain (Dec 20, 2019)
• Comet Holmes (17P/Holmes) (Feb 19, 2021)
• Comet Brooks 2 (Apr 18, 2021)
• Comet Pons-Winnecke (May 27, 2021)
• Comet Finlay (Jul 13, 2021)
• Comet d'Arrest (Sept 21, 2021)
• Comet Faye (4P/Faye) (Dec 2021)
• Comet 67P/Churyumov-Gerasimenko (Jan 21, 2022)
• Halley’s Comet (1P/Halley) (July 28, 2061)
• Swift-Tuttle Comet (109P/Swift-Tuttle) (July 12, 2126)
• Comet Lovejoy (C/2011 W3) (2633 CE)
• Comet Ikeya-Seki (C/1965 S1) (2565 CE)
• Comet Hale-Bopp (C/1995 O1) (4385 CE)
• Comet LINEAR (˜32000 CE)
• Comet Hyakutake (C/1996 B2) (˜72000 CE)