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The Kreutz group of sungrazing comets may be fragments of a Sungrazer Parent Comet with diameter 120 km that Brian Marsden has calculated to have appeared between 20,000 and 10,000 years ago. The Sungrazer Parent would have had a period of about 1,000 years, and fragmentation would have occurred between 10 and 20 periods ago. Here, I use a rough figure of 10,000 BC for the fragmentation time. As the Sungrazers come very close to the Sun (some of them even hitting it, and so being Sunstrikers), they are very bright (Sungrazer Parent absolute magnitude -5.0) and very fast (on the order of 600 km/sec) at perihelion. Brian Marsden calculates that when the Sungrazer Parent fragmented, it split into two major groups, denoted I and II. Kreutz Sungrazer Group 1 held together until 371 BC, when it split into at least 3 pieces, one of which was the Great March Comet of 1843. Kreutz Sungrazer Group II held together until 1106 AD, when it split into at least 3 pieces, including the Great September Comet of 1882 and Comet Ikeya-Seki of 1965. In the following table, ? denotes uncertainty as to which Kreutz group a comet belongs and ?? denotes uncertainty as to whether a comet is a Kreutz sungrazer. Perihelion Comet Kreutz Perihelion Date Group Distance (km) 10,000 BC Sungrazer Parent 371 BC Aristotle I? 4 Feb 1106 II? 1 Mar 1668 ?? 1,500,000 2 Dec 1689 Richaud ?? 1,500,000 23 Oct 1695 Jacob ?? 1,500,000 15 Feb 1702I Jacob ?? 1,500,000 27 Feb 1843I Great March Comet I 827,000 28 Jan 1880I Great Southern Comet I 822,000 17 Sep 1882II Great September Comet II 1,160,000 11 Jan 1887I Great Southern Comet ? 723,000 27 Dec 1945VII Du Tolt II? 1,124,000 23 Aug 1963V Pereyra I 758,000 21 Oct 1965VIII Ikeya-Seki II 1,165,000 14 May 1970VI White-Ortiz-Bolelli II 1,328,000 30 Aug 1979XI Solwind 1 II? 720,000 A sungrazer that hits the Sun is called a Sunstriker. Douglas Biesecker has an excellent web-page about Sungrazers. Thanks to him for correcting an error I had on the Perihelion Distance of 1979XI. The figure above is now roughly correct, I think. It means that 1979XI was not a Sunstriker, but was a Sungrazer that came very close to the photosphere. As he says, as of 15 May 1997, "... 23 sun-grazers [have been] discovered since ... 1979XI ...". His page is not only about Sungrazers, but covers much more about astrophysics, especially Solar astrophyics.
Much of the information on this page comes from Fred Schaaf's 1997 book, Comet of the Century.
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