Lost comet

Biela's Comet was seen in two pieces in 1846, and has not been observed since 1852

A lost comet is a previously discovered comet that has been missed at its most recent perihelion passage, generally because there is not enough data to calculate reliably the comet's orbit and predict its location. The "D/" designation is for a periodic comet that no longer exists or is deemed to have disappeared.

Lost comets can be compared to lost asteroids, although calculation of cometary orbits differs because of nongravitational forces that can affect comets, such as emission of jets of gas from the nucleus. Some astronomers have specialized in this area, such as Brian G. Marsden, who successfully predicted the 1992 return of the once-lost periodic comet Swift–Tuttle.

Reasons for loss

5D/Brorsen, which was lost after its 1879 apparition.

There are a number of reasons why a comet might be missed by astronomers during subsequent apparitions. Firstly, cometary orbits may be perturbed by interaction with the giant planets, such as Jupiter. This, along with nongravitational forces, can result in changes to the date of perihelion. Alternatively, it is possible that the interaction of the planets with a comet can move its orbit too far from the Earth to be seen or even eject it from the Solar System, as is believed to have happened in the case of Lexell's Comet. As some comets periodically undergo "outbursts" or flares in brightness, it may be possible for an intrinsically faint comet to be discovered during an outburst and subsequently lost.

Comets can also run out of volatiles. Eventually most of the volatile material contained in a comet nucleus evaporates away, and the comet becomes a small, dark, inert lump of rock or rubble, an extinct comet that can resemble an asteroid (see Comets § Fate of comets). This may have occurred in the case of 5D/Brorsen, which was considered by Marsden to have probably "faded out of existence" in the late 19th century.

Material coming off Component B of 73P/Schwassmann–Wachmann which broke up starting in 1995, as seen by the Hubble Space Telescope.

Comets are in some cases known to have disintegrated during their perihelion passage, or at other points during their orbit. The best-known example is Biela's Comet, which was observed to split into two components before disappearing after its 1852 apparition. In modern times 73P/Schwassmann–Wachmann has been observed in the process of breaking up.

Occasionally, the discovery of an object turns out to be a rediscovery of a previously lost object, which can be determined by calculating its orbit and matching calculated positions with the previously recorded positions. In the case of lost comets this is especially tricky. For example, the comet 177P/Barnard (also P/2006 M3), discovered by Edward Emerson Barnard on June 24, 1889, was rediscovered after 116 years in 2006. On July 19, 2006, 177P came within 0.36 AU of the Earth.

Comets can be gone but not considered lost, even though they may not be expected back for hundreds or even thousands of years. With more powerful telescopes it has become possible to observe comets for longer periods of time after perihelion. For example, Comet Hale–Bopp was observable with the naked eye about 18 months after its approach in 1997. It is expected to remain observable with large telescopes until perhaps 2020, by which time it will be nearing 30th magnitude.

Comets that have been lost or which have disappeared have names beginning with a "D" according to current IAU conventions.

Table

Comets are typically observed on a periodic return. When they do not they are sometimes found again, while other times they may break up into fragments. These fragments can sometimes be further observed, but the comet is no longer expected to return. Other times a comet will not be considered lost until it does not appear at a predicted time. Comets may also collide with another object, such as Comet Shoemaker–Levy 9, which collided with Jupiter in 1994.

Name(s)	Initially discovered	Period (years)	Last seen	Recovered	Fate
D/1770 L1 (Lexell)	1770	5.6			Probably lost due to a 1779 close encounter with Jupiter which might have greatly perturbed the orbit or even ejected the comet from the Solar System
3D/Biela	1772	6.6	1852		Broke up in two fragments (1846), then thousands, creating the Andromedids meteor shower
27P/Crommelin	1818	27.9	1873	1928	Three independent discoveries linked by Crommelin in 1930
289P/Blanpain	1819	5.2		2003	Lost since 1819 discovery due to faintness; rediscovered in 2003 thanks to good viewing conditions; first identified as asteroid 2003 WY25, subsequently matched to the 1819 comet after 184 years and 35 orbits; confirmed by observations in 2013 and 2014 near perihelion; probable source of the Phoenicids meteor shower observed since 1956
273P/Pons–Gambart	1827	180		2012	Period of roughly 64±10 years originally computed in 1917 was wrong; rediscovered after 185 years in a single orbit; possibly matches a Chinese observation in 1110
54P/de Vico–Swift–NEAT	1844	7.3	1894, 1965	2002	Lost several times due to perturbations by Jupiter
122P/de Vico	1846	74.4		1995	Not observed on first predicted return in 1921; recovered in 1995 after 149 years and 2 orbits
5D/Brorsen	1846	5.5	1879		Lost since 1879 despite good orbit computations
80P/Peters–Hartley	1846	8.1		1982	Recovered in 1982 after 136 years and 17 orbits; regularly observed since then
20D/Westphal	1852	61.9	1913		Expected in 1976 but not observed; next possible return in 2038
109P/Swift–Tuttle	1862	133.3		1992	Recovered after 130 years as predicted in 1971 by Brian G. Marsden; retroactively matched to observations of 1737 in Europe and 188 AD and 68 BC in China; source of the Perseids meteor shower
55P/Tempel–Tuttle	1865	33.2		1965	Recovered in 1965 after 99 years and 3 orbits; matches earlier observations of 1366 and 1699; source of the Leonids meteor shower
11P/Tempel–Swift–LINEAR	1869	6.4	1908	2001	Recovered in 2001 after 93 years and 15 orbits; not observed in 2008 due to solar conjunction but seen again in 2014 as predicted
72P/Denning–Fujikawa	1881	9.0	1978	2014	Recovered in 1978 after 97 years and 11 orbits, then lost again and recovered in 2014 after 4 more orbits
15P/Finlay	1886	6.5	1926	1953	Regularly observed since 1953
177P/Barnard	1889	118.8		2006	Recovered after 117 years in a single orbit
206P/Barnard–Boattini	1892	5.8		2008	Recovered in 2008 after 116 years and 20 orbits; not seen on predicted return in 2014; next perihelion in 2021
17P/Holmes	1892	6.9	1906	1964	Regularly observed since 1964; large outburst in 2007
205P/Giacobini (D/1896 R2)	1896	6.7		2008	Recovered in 2008 after 112 years and 17 orbits; seen in 2015 as predicted; three visible fragments
18D/Perrine–Mrkos	1896	6.75	1909, 1968	1955	Lost after 1909, recovered in 1955 and lost again since 1968
113P/Spitaler	1890	7.1		1993	Recovered in 1993 after 103 years and 15 orbits; regularly observed since 1994 perihelion
97P/Metcalf–Brewington	1906	10.5		1991	Recovered in 1991 after 84 years and 11 orbits; orbital period lengthened by Jupiter in 1993
69P/Taylor	1915	6.95		1976	Recovered in 1976 after 61 years and 9 orbits; regularly observed since 1977 perihelion
25D/Neujmin	1916	5.4	1927		Only seen twice; lost since 1927
34D/Gale	1927	11.0	1938		Only seen twice; lost since 1938
73P/Schwassmann–Wachmann	1930	5.4		1979	Broke up into 4 fragments in 1995 and dozens in 2006, yielding the Tau Herculids meteor shower
57P/du Toit–Neujmin–Delporte	1941	6.4		1970	Recovered in 1970 after 29 years and 5 orbits; observed regularly since 1983
107P/Wilson–Harrington	1949	4.3		1992	Lost for 30 years; rediscovered as a Mars-crosser asteroid in 1979; equated with the lost comet in 1992 while searching for precovery images
271P/van Houten–Lemmon	1966	18.5		2012	First discovered on plates from 1960; recovered in 2012 after 3 orbits; perihelion in 2013
75D/Kohoutek	1975	6.6	1988		Only seen three times; lost since 1988
157P/Tritton	1978	6.4		2003	Recovered in 2003 after 25 years and 4 orbits; regularly observed since then
83D/Russell	1979	6.1	1985		Only seen twice; lost since 1985, probably due to a close encounter with Jupiter in 1988

See also

• List of periodic comets
• List of non-periodic comets
• Lost asteroids
• Brian G. Marsden, comet orbit expert
• The Lost Comet (1964), book by Stanton A. Coblentz

External links

• Lost periodic comets on Maik Meyer's home page