Lost asteroids

Designation Year of discovery recovery 132 Aethra 1873 1922 1892 X (330 Adalberta) 1892 false positive  452 Hamiltonia 1899 1987 473 Nolli 1901 1987 719 Albert 1911 2000 724 Hapag 1911 1988 843 Nicolaia 1916 1981 878 Mildred 1916 1991 1009 Sirene 1923 1982 1026 Ingrid 1923 1986 1179 Mally 1931 1986

Name Year of discovery recovery 1537 Transylvania 1940 1981 1862 Apollo 1932 1973 1916 Boreas 1953 1976 1922 Zulu 1949 1974 2101 Adonis 1936 1977 3494 Purple Mountain 1962 1980 3789 Zhongguo 1928 1986 7796 Járacimrman 1973 1996 (29075) 1950 DA 1950 2000 69230 Hermes 1937 2003

Designation Year of Notes discovery recovery 1927 LA  1927 still lost Observed 4 times between 1 June 1927 and 5 July 1927, MPC 1991 BA 1991 still lost Passed within a lunar distance of Earth 1993 HD 1993 still lost Near-Earth asteroid, MPC 1995 SN55 1995 still lost May be the largest centaur 2007 WD5 2007 still lost Passed close to Mars 6344 P–L 1960 2007 Potentially hazardous object; probably a dormant comet

Lost minor planets are minor planets that observers lose track of due to too short an observation arc to accurately predict the future location of the minor planet. Many of the asteroids that were discovered early were lost and rediscovered in the 1980s and 1990s, but a number of minor planets continue to be lost. By some definitions, thousands, if not tens of thousands observed minor planets are lost—they cannot be found by pointing an appropriate telescope at their predicted location, because the uncertainty in their predicted orbit is too large or they are currently too faint to be detected.

Some minor planets and comets discovered in previous decades were "lost" because the observational data obtained was insufficient to determine a reliable orbit. Without this information, astronomers would not know where to look for the object at future dates. Occasionally, a "newly discovered" object turns out to be a rediscovery of a previously lost object. This can be determined by calculating the "new" object's orbit (once it is firmly known) backwards and checking its past positions against those previously recorded for the lost object. This may greatly extend the observation arc, thus fixing the orbit much more precisely. For lost comets the back orbit calculations are especially tricky because of nongravitational forces that can affect their orbits, such as emission of jets of gas from the comet nucleus. However, Brian G. Marsden has specialized in calculating such nongravitational forces. Notably, he successfully predicted the 1992 return of the once-lost periodic comet Swift–Tuttle.

This is a small selection of some early lost or notable asteroids with their discovery and rediscovery dates. (A more detailed description for some of these minor planets can be found in the following sections). The true number of lost asteroids may be over 150,000. There are also about 30,000 unnumbered bodies with a condition code of U = 9, indicating the highest possible uncertainty of their orbit determination. Many of these bodies have been observed years if not decades ago and must be considered lost. There are also more than a thousand near-Earth objects (NEOs) with an observation arc of one or two days only.

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