List Of Periodic Comets
Periodic comets are comets having orbital periods of less than 200 years (also known as "short-period comets") or which have been observed during more than a single perihelion passage (e.g. 153P/Ikeya–Zhang). ("Periodic comet" is also sometimes used to mean any comet with a periodic orbit, even if greater than 200 years.)
In nearly all cases, comets are named after their discoverer(s), but in a few cases such as 2P/Encke and 27P/Crommelin they were named for a person who calculated their orbits (the orbit computers). The long-term orbits of comets are difficult to calculate because of errors in the known trajectory that accumulate with perturbations from the planets, and in the days before electronic computers some people dedicated their entire careers to this. Even so, quite a few comets were lost because their orbits are also affected by non-gravitational effects such as the release of gas and other material that forms the comet's coma and tail. Unlike a long-period comet, the next perihelion passage of a numbered periodic comet can be predicted with a high degree of accuracy.
Periodic comets sometimes bear the same name repeatedly (e.g. the nine Shoemaker–Levy comets or the twenty-four NEAT comets); the IAU system distinguishes between them either through the number prefix or by the full designation (e. g. 181P and 192P are both "Comet Shoemaker–Levy"). In the literature, an informal numbering system is applied to periodic comets (skipping the non-periodic ones), thus 181P and 192P are known as Comet Shoemaker–Levy 6 and Comet Shoemaker–Levy 1, respectively. Non-periodic Shoemaker–Levy comets are interleaved in this sequence: C/1991 B1 between 2 and 3, C/1991 T2 between 5 and 6, C/1993 K1 and C/1994 E2 after Shoemaker–Levy 9.
In comet nomenclature, the letter before the "/" is either "C" (a non-periodic comet), "P" (a periodic comet), "D" (a comet which has been lost or has disintegrated), "X" (a comet for which no reliable orbit could be calculated —usually historical comets), or "A" for an object that was mistakenly identified as a comet, but is actually a minor planet.
Some lists retain the "C" prefix for comets of periods larger than about 30 years until their return is confirmed.
Other articles related to "list of periodic comets, comet":
... Comet Discoverer(s) or Namesake P/2006 VW139 = minor planet 300163 Spacewatch P/2011 N1 (ASH) de la Cueva, Ortiz, Santos Sanz Morales D/1884 O1 (Barn ...
Famous quotes containing the words list of, comets, list and/or periodic:
“Modern tourist guides have helped raised tourist expectations. And they have provided the nativesfrom Kaiser Wilhelm down to the villagers of Chichacestenangowith a detailed and itemized list of what is expected of them and when. These are the up-to- date scripts for actors on the tourists stage.”
—Daniel J. Boorstin (b. 1914)
No answer to the childrens cry
Of echos answer and the man of frost
And ghostly comets over the raised fists.”
—Dylan Thomas (19141953)
“Every morning I woke in dread, waiting for the day nurse to go on her rounds and announce from the list of names in her hand whether or not I was for shock treatment, the new and fashionable means of quieting people and of making them realize that orders are to be obeyed and floors are to be polished without anyone protesting and faces are to be made to be fixed into smiles and weeping is a crime.”
—Janet Frame (b. 1924)
“It can be demonstrated that the childs contact with the real world is strengthened by his periodic excursions into fantasy. It becomes easier to tolerate the frustrations of the real world and to accede to the demands of reality if one can restore himself at intervals in a world where the deepest wishes can achieve imaginary gratification.”
—Selma H. Fraiberg (20th century)