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Encyclopedia > Great comet

A Great Comet is a comet which becomes particularly bright and it is very spectacular to be noticed by a casual observer. A great comet ussually (but not always) appears about every decade. Download high resolution version (800x1174, 790 KB) ©  This image is copyrighted. ... Download high resolution version (800x1174, 790 KB) ©  This image is copyrighted. ... Comet West formally designated C/1975 V1, 1976 VI, and 1975n, was a spectacular comet, sometimes considered to qualify for the status of great comet. It was discovered by Richard M. West on August 10, 1975 and reached peak brightness in March 1976. ... Comet Hale-Bopp Comet West For other uses, see Comet (disambiguation). ... A decade is a set or a group of ten, commonly a period of 10 years in contemporary English, or a period of 10 days in the French revolutionary calendar. ...


Predicting whether a comet will become a great comet is notoriously difficult, as many factors may cause a comet's brightness to depart drastically from predictions. Broadly speaking, if a comet has a large and active nucleus, will pass close to the Sun, and is not obscured by the Sun as seen from the Earth when at its brightest, it will have a chance of becoming a great comet.


While comets are officially named after their discoverers, some may come to be referred to as The Great Comet of... the year in which they were brightest.

Contents

What defines a Great Comet?

The definition of a great comet could obviously be quite subjective. However, any comet which becomes bright enough to be noticed by people who are not actively looking for it and becomes well known outside the astronomical community may come to be known as a great comet.


To most people, however, a great comet is simply a beautiful spectacle.


Reasons comets become great comets

The vast majority of comets are never bright enough to be seen by the naked eye. They generally pass through the inner solar system unseen by anyone except astronomers. However, occasionally, a comet may brighten to naked eye visibility, and even more rarely it may become as bright or brighter than the brightest stars. How bright a comet becomes depends on three main factors. Image File history File linksMetadata Size of this preview: 648 × 519 pixelsFull resolution (648 × 519 pixel, file size: 107 KB, MIME type: image/jpeg)Taken by nasa as stated here [1]. Retiono Virginian 15:51, 24 April 2007 (UTC) File history Legend: (cur) = this is the current file, (del) = delete... Image File history File linksMetadata Size of this preview: 648 × 519 pixelsFull resolution (648 × 519 pixel, file size: 107 KB, MIME type: image/jpeg)Taken by nasa as stated here [1]. Retiono Virginian 15:51, 24 April 2007 (UTC) File history Legend: (cur) = this is the current file, (del) = delete... Comet Hyakutake (Japanese: 百武彗星 Hyakutake suisei, IPA ; formally designated C/1996 B2) is a comet that was discovered in January 1996, and passed very close to the Earth in March of that year. ... Major features of the Solar System (not to scale; from left to right): Pluto, Neptune, Uranus, Saturn, Jupiter, the asteroid belt, the Sun, Mercury, Venus, Earth and its Moon, and Mars. ... An astronomer or astrophysicist is a scientist whose area of research is astronomy or astrophysics. ...


Size and activity of the nucleus

Cometary nuclei vary in size from a few hundreds of metres across or less to many kilometres across. When they approach the sun, large amounts of gas and dust are ejected by cometary nuclei, due to solar heating. A crucial factor in how bright a comet becomes is how large and how active its nucleus is. After many returns to the inner solar system, cometary nuclei become depleted in volatile materials and thus are much less bright than comets which are making their first passage through the solar system.


Close perihelion approach

The brightness of a simple reflective body varies with the inverse square of its distance from the sun. That is, if an object's distance from the sun doubles, its brightness is quartered. However, comets behave differently due to their ejection of large amounts of volatile gas which then also reflect sunlight and may also fluoresce. Their brightness varies roughly as the inverse cube of their distance from the sun, meaning that if a comet's distance from the sun is halved, it will become eight times as bright. Fluorescence induced by exposure to ultraviolet light in vials containing various sized Cadmium selenide (CdSe) quantum dots. ...


This means that the peak brightness of a comet depends significantly on its distance from the sun. For most comets, the perihelion of their orbit lies outside the earth's orbit. Any comet approaching the sun to within 0.5 AU or less may have a chance of becoming a Great Comet. This article is about several astronomical terms (apogee & perigee, aphelion & perihelion, generic equivalents based on apsis, and related but rarer terms. ... The astronomical unit (AU or au or a. ...


Close approach to the Earth

For a comet to become spectacular, it also needs to pass close to the Earth. Comet Halley, for example, is usually very bright when it passes through the inner solar system every 76 years, but during its 1986 apparition, its closest approach to earth was almost the most distant possible. The comet became visible to the naked eye, but was definitely unspectacular. Image File history File links Download high-resolution version (1254x961, 487 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Comet Halley ... Image File history File links Download high-resolution version (1254x961, 487 KB) File links The following pages on the English Wikipedia link to this file (pages on other projects are not listed): Comet Halley ... Comet Halley, officially designated 1P/Halley, more generally known as Halleys Comet after Edmond Halley, is a comet that can be seen every 75-76 years. ... Comet Halley, officially designated 1P/Halley, more generally known as Halleys Comet after Edmond Halley, is a comet that can be seen every 75-76 years. ... 1986 (MCMLXXXVI) was a common year starting on Wednesday of the Gregorian calendar. ... Generally, an apparition is act or instance of appearing. ...


A comet fulfilling all three of these criteria will certainly be spectacular. Sometimes, a comet failing on one criterion will still be extremely impressive. For example, Comet Hale-Bopp had an exceptionally large and active nucleus, but did not approach the sun very closely at all. Despite this it still became an extremely famous and well observed comet. Equally, Comet Hyakutake was a rather small comet, but became bright because it passed extremely close to the earth. Comet Hale-Bopp (formally designated C/1995 O1) was probably the most widely observed comet of the twentieth century, and one of the brightest seen for many decades. ... Comet Hyakutake (Japanese: 百武彗星 Hyakutake suisei, IPA ; formally designated C/1996 B2) is a comet that was discovered in January 1996, and passed very close to the Earth in March of that year. ...


Previous Great Comets

Great Comets of the past two centuries have included the following:

Great Comets of more than two centuries ago have included the following: The Great Comet of 1811 (formally designated C/1811 F1) was a comet that was visible to the naked eye for around 260 days. ... The Great Comet of 1843 was a comet which became very bright in March 1843. ... Comet Donati, or Donatis Comet, formally designated C/1858 L1 and 1858 VI, was a comet named after the Italian astronomer Giovanni Battista Donati who first observed it on June 2, 1858. ... 1858 (MDCCCLVIII) is a common year starting on Friday of the Gregorian calendar (or a common year starting on Sunday of the 12-day-slower Julian calendar). ... The Great Comet of 1861 (formally designated C/1861 J1) was a comet that was visible to the naked eye for approximately 3 months. ... The Great Comet of 1882 was a comet which became very bright in September 1882. ... Halleys Comet, officially designated 1P/Halley and also referred to as Comet Halley after Edmond Halley, is a comet that can be seen every 75-76 years. ... 1910 (MCMX) was a common year starting on Saturday (link will display calendar) of the Gregorian calendar or a common year starting on Sunday of the 13-day slower Julian calendar. ... The Great Daylight Comet of 1910 was a great comet which upstaged the much-anticipated appearance of Halleys Comet in the same year. ... Comet Skjellerup-Maristany was a comet which became very bright in 1927. ... Year 1927 (MCMXXVII) was a common year starting on Saturday (link will display full calendar) of the Gregorian calendar. ... Comet Arend-Roland was a comet which appeared in 1957 and became very bright as it passed through the inner solar system. ... 1957 (MCMLVII) was a common year starting on Tuesday of the Gregorian calendar. ... 1962 (MCMLXII) was a common year starting on Monday (the link is to a full 1962 calendar). ... Comet Ikeya-Seki (C/1965 S1) was a comet discovered independently by Kaoru Ikeya and Tsutomu Seki. ... 1965 (MCMLXV) was a common year starting on Friday (the link is to a full 1965 calendar). ... Comet Bennett, formally known as C/1969 Y1, was one of two brilliant comets to grace the 1970s, along with Comet West. ... 1970 (MCMLXX) was a common year starting on Thursday. ... Comet West formally designated C/1975 V1, 1976 VI, and 1975n, was a spectacular comet, sometimes considered to qualify for the status of great comet. It was discovered by Richard M. West on August 10, 1975 and reached peak brightness in March 1976. ... 1976 (MCMLXXVI) was a leap year starting on Thursday. ... Comet Hyakutake (Japanese: 百武彗星 Hyakutake suisei, IPA ; formally designated C/1996 B2) is a comet that was discovered in January 1996, and passed very close to the Earth in March of that year. ... 1996 (MCMXCVI) was a leap year starting on Monday of the Gregorian calendar, and was designated the International Year for the Eradication of Poverty. ... Comet Hale-Bopp (formally designated C/1995 O1) was probably the most widely observed comet of the twentieth century, and one of the brightest seen for many decades. ... 1997 (MCMXCVII) was a common year starting on Wednesday of the Gregorian calendar. ... C/2006 P1, also known as Comet McNaught, is a non-periodic comet discovered on August 7, 2006 in Australia by Robert H. McNaught[1]. It made perihelion on January 12, 2007, and has become easily visible to the naked eye. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ...

X/1106 C1, also known as the Great Comet of 1106, was seen in Wales as well as Japan, Korea, China and Europe. ... Events September 14 - Battle of Homildon Hill. ... Events First Portuguese governor was appointed to Macau The Swedish city Karlskrona was founded as the Royal Swedish Navy relocated there. ... The Great Comet of 1729, also known as C/1729 P1, is a non-Periodic Comet with an absolute magnitude of -3, the brightest absolute magnitude ever observed. ...

External links

  • Great Comets in History (NASA website), Donald K. Yeomans (April 1998), Jet Propulsion Laboratory/California Institute of Technology

  Results from FactBites:
 
NationMaster - Encyclopedia: Great Comet of 1861 (722 words)
The Great Comet of 1861 (formally designated C/1861 J1) was a comet that was visible to the naked eye for approximately 3 months.
It was categorized as a Great Comet, one of eight in the 19th century.
Comet Hale-Bopp A comet is a small body in the solar system that orbits the sun and (at least occasionally) exhibits a coma (or atmosphere) and/or a tail — both due primarily to the effects of solar radiation upon the comets nucleus, which itself is a minor planet...
The Great Comets of 1996 and 1997 (1216 words)
The Comet Observations Home Page at JPL has up-to-date information on all comets visible to amateurs (with telescopes 16" or less) including collections of observer reports, ephemerides, finder charts, etc. Go here to find out about the next "Instant Comet" before it is too late.
This comet is still being observed and is still producing jets that produce the "pinwheel" appearance that is the hallmark of this comet.
In the Hale-Bopp encounter, the truly great "comet flap" was the story of the Saturn Shaped UFO near Hale-Bopp.
  More results at FactBites »

 
 

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