The term "Great Comet"
- Several posters have asked why they have not heard the
appellation "Great Comet" applied to C/2006 P1, or perhaps at what
point in time it would become appropriate to do so. Thus, perhaps
this is a good opportunity to caralify the term.
Historically, the name "Great Comet" has been applied most often to
objects of great brilliance and spectacular appearance that appearred
suddenly out of the twilight and were "discovered" simultaneously
throughout the world. Less often, the name has been unsed in
conjunction with particularly bright and impressive objects to set
them appart from all others seen around a certain time, as in the
Great Comet of 1811 (Comet Flaugergeus) or The Great September Comet
of 1882 (Comet Cruls). Typically, however, when a comet has been
discovered well before it became spectacular, even if eventually
visible in daylight, it remains known simply by the discoverer's
name, as with Comet Hind (1847) or Comet Donati (1858).
Incidentally, while the name of a month is sometimes included in a
comet's official name, as with the Great March Comet (1843) or the
Great September Comet (1882), a discoverer's name is never used in
conjunction with "Great Comet", as in McNaught's Great Comet or Great
The usage of the term "Great Comet" peaked during the 19th century
and has rarely been applied over the past hundred years. The only
notable exception being the Great January Comet of 1910 (sometimes
called the Daylight Comet of 1910). The brilliant comets of 1947 and
1948, discovered simultaneously by thousands, are referred to as The
Southern Comet and The Eclipse Comet, respectively. An interesting
footnote, however, is that Brian Marsden of the IAU Central Telegram
Bureau, the body officially charged with naming comets, once referred
unofficial to Comet Ikeya-Seki as "The Great Comet of 1965" in the
pages of Sky & Telescope magazine.
Nevertheless, the brilliant comets Skjellerup-Maristany, Arend-
Roland, Ikeya-Seki, Bennett, West, Hale-Bopp, and Hyakutake (which
certainly deserves the title of Great Comet if any ever did) are
officially known simply by their discoverer's names. Nevertheless, to
comet observers and writers of astronomical literature, these are all
considered member of a group of spectacular objects informally
called "Great Comets".
Thus, we honestly have two usages of the term "Great Comet": one for
official use in orbital catalogs, lists and such and another,
informal but classical, to indentify or group a number of spectacular
objects clearly set appart from their more mundane brethern. So, you
may choose to call C/2006 P1 what you may but do choose understanding
As for me....well, to me C/2006 P1 will always be remembered as The
Great Daylight Comet of 2007.