Lost asteroids or lost planets are asteroids that observers lose track of after discovering. Many early lost asteroids were rediscovered in the 1980s and 1990s, but a number of asteroids and other types of small Solar System bodies continue to be lost.[1] By some definitions, about half of all discovered asteroids are lost because they cannot be found by pointing an appropriate telescope at their predicted location.[2]
Some asteroids and comets discovered in previous decades were "lost" because not enough observational data had been obtained 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 backwards and checking its past positions against those previously recorded for the lost object. In the case of lost comets this is 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.
Lost asteroids can be used for other things as well. For example, observations of asteroids around 20 AU may provide insights into the Pioneer anomaly.[3][4]
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The number of asteroids that were only observed once and not re-observed grew throughout the 19th and 20th century, but improved telescopes, searches, and detection techniques lead to most of these cases being resolved in the 1970s, 80s, and 90s. There are earlier examples also, such as 132 Aethra, which was lost between 1873 and 1922.[5]
1862 Apollo is a Q-type asteroid, discovered by Karl Reinmuth in 1932, but lost and not recovered until 1973. Another Apollo asteroid is 2101 Adonis, discovered by Eugene Delporte in 1936 and lost until 1977 when it was rediscovered by Charles T. Kowal. It was also one of the first near-Earth asteroids to be discovered.
1916 Boreas (1953 RA), an Amor asteroid, was discovered on 1 September 1953 by Sylvain Julien Victor Arend at the Royal Observatory of Belgium,[6] and rediscovered in 1974 by Richard Eugene McCrosky, G. Schwartz and JH Bulger based on a predicted position by Brian G. Marsden.[6][7]
1922 Zulu (1949 HC) is an outer main-belt asteroid discovered on 25 April 1949 by Ernest Leonard Johnson at Johannesburg (UO).[8] It is one of very few asteroids located in the 2 : 1 mean motion resonance with Jupiter.[9] This asteroid was lost shortly after discovery and only rediscovered in 1974 by Richard Eugene McCrosky, Cheng-yuan Shao and JH Bulger based on a predicted position by C. M. Bardwell of the Cincinnati Observatory.[7][6]
L. K. Kristensen at the University of Aarhus rediscovered 452 Hamiltonia and 1537 Transylvania, along with numerous other small objects, in 1981.[10] At the time these results were published, only nine numbered minor planets remained unobserved since their discoveries: 330 Adalberta, 473 Nolli, 719 Albert, 724 Hapag, 843 Nicolaia, 878 Mildred, 1009 Sirene, 1026 Ingrid, and 1179 Mally.[10]
843 Nicolaia was rediscovered at the Heidelberg Astronomisches Rechen-Institut in 1981.[11]
473 Nolli was discovered by Max Wolf on 13 February 1901, but it remained lost for many decades until it was recovered finally in 1987 IAUC 4292, 86 years later.
878 Mildred was originally discovered in 1916 using the 1.5 m (60-inch) Hale Telescope at the Mount Wilson Observatory, but was subsequently lost until it was again observed on single nights in 1985 and 1991.[12][13]
724 Hapag and 719 Albert had first been found by Johann Palisa in 1911. Hapag was given the provisional name 1911 NC,[14] but lost until it was rediscovered in 1988. Due to inaccuracies in its computed orbit, Albert was also lost and not recovered until 2000, when Jeffrey A. Larsen located it using data from the Spacewatch asteroid survey project.[12] At the time of its rediscovery, Albert was the last remaining "lost asteroid" among those assigned numbers (69230 Hermes was not numbered until 2003).[12]
1009 Sirene was recovered in 1982 by J. Gibson using exposures form the 48-inch (120 cm) Schmidt telescope at Palomar Observatory, and he revised its ephemeris.[15]
1026 Ingrid was discovered by Karl Wilhelm Reinmuth on 13 August 1923 and given the provisional designation 1923 NY.[6][6] It was reidentified in 1986 by Syuichi Nakano.[16]
1179 Mally was discovered by Max Wolf on 19 March 1931 and given the provisional designation 1931 FD.[6] It was rediscovered in 1986 by Lutz D. Schmadel, Richard Martin West and Hans-Emil Schuster.[17]
While studying in Chicago in 1928, Zhang Yuzhe discovered an asteroid that was given the provisional designation 1928 UF, and later the number 1125. He named it "China" or "中華" (Zhōnghuá). However, this asteroid was not observed beyond its initial appearance and a precise orbit could not be calculated. In 1957, the Purple Mountain Observatory in China discovered a new asteroid, and with Zhang Yuzhe's agreement the new object 1957 UN1 was re-assigned the official designation 1125 China in place of the lost 1928 UF. However, in 1986, the newly discovered object 1986 QK1 was confirmed to be a rediscovery of the original 1928 UF, and this object was named 3789 Zhongguo (also a name for China).[18]
Asteroid (29075) 1950 DA was discovered on 23 February 1950 by Carl A. Wirtanen at Lick Observatory. It was observed for 17 days and then lost, since not enough observations were made to allow its orbit to be plotted. It was then rediscovered on 31 December 2000. The chance it will impact Earth on 16 March 2880 during its close approach has been estimated as 1 in 300, roughly 50% greater than that for all other such objects combined between now and 2880.[19] It has a diameter of about a kilometer (.6 miles).
7796 Járacimrman was discovered at Kleť Observatory (Czech Republic) on 16 January 1996 by Zdeněk Moravec and was designated 1996 BG. It was observed until April 1996 and then in June and July 1997. It was revealed, by precovery, to be a lost asteroid which had previously been observed twice: at the Brera-Merate Observatory in northern Italy on 12 December 1973 and at Mount Stromlo Observatory (near Canberra, Australia) on 8 and 9 July 1990.
2007 WD5 is a 50 m (160 ft) Apollo-class[20] near-Earth object and a Mars-crosser asteroid discovered on 20 November 2007 by Andrea Boattini of the Catalina Sky Survey. Early observations of 2007 WD5 caused excitement amongst the scientific community when it was estimated as having as high as a 1 in 25 chance of colliding with Mars on 30 January 2008.[21] However, by 9 January 2008 additional observations allowed NASA's Near Earth Object Program (NEOP) to reduce the uncertainty region resulting in only a 1-in-10,000 chance of impact.[22] 2007 WD5 most likely passed Mars at a distance of 6.5 Mars radii. Due to this relatively small distance and the uncertainty level of the prior observations, the gravitational effects of Mars on its trajectory are unknown and, according to Steven Chesley of NASA's Jet Propulsion Laboratory Near Earth Object program, 2007 WD5 is currently considered "lost".[21][23] The best fit trajectory had the asteroid passing within 21,000 km of Mars and only 16,000 km from the moon Deimos.[22][24]
In the search for various types of near-Earth object, such as quasi-satellites and Earth-crosser asteroids, objects that may correspond to some lost sightings include 2006 RH120 or 3753 Cruithne, among others.
In 2007, the object 2007 RR9 was found to be the asteroid 6344 P-L, lost since 1960.[25] It is a potentially hazardous object and probably a dormant comet, although it was not visibly outgassing at that time.[25]
Some lost asteroids turn out to be erroneous observations, as in the case of 330 Adalberta. This designation was originally given to 1892 X, but reassigned to A910 CB when 1892 X turned out to be a false positive in the 1980s.[26]
Default list is in increasing order of minor planet number (see List of minor planets). This is really just a small selection of early lost asteroids that were recovered, with some additional examples because the true number of lost asteroids by some definitions is over 150000.[2]
| Name(s) | Discovered | Rediscovered |
|---|---|---|
| 132 Aethra | 1873 | 1922[5] |
| 330 Adalberta (1892 X) | 1892 | Error |
| 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[15] |
| 1026 Ingrid | 1923 | 1986 |
| 1179 Mally | 1931 | 1986 |
| 1537 Transylvania | 1940 | 1981 |
| 1862 Apollo | 1932 | 1973 |
| 1916 Boreas | 1953[6] | 1976 |
| 1922 Zulu | 1949 | 1974 |
| 2101 Adonis | 1936 | 1977 |
| 3494 Purple Mountain | 1962 | 1980 |
| 3789 Zhongguo | 1928 | 1986 |
| 6344 P-L | 1960 | 2007[25] |
| 7796 Járacimrman | 1973 | 1996 |
| 29075 1950 DA | 1950 | 2000 |
| 69230 Hermes | 1937 | 2003 |
A very small[2] selection of lost asteroids with provisional designations.
| Name(s) | Discovered | Rediscovered | Note |
|---|---|---|---|
| 1991 BA | 1991 | Lost | Passed within a lunar distance of Earth |
| 1993 HD | 1993 | Lost[28] | Near-Earth asteroid |
| 1995 SN55 | 1995 | Lost | May be the largest centaur |
| 2004 PR107 | 2004 | Lost[29] | Cubewano; a dwarf-planet candidate |
| 2006 HH123 | 2006 | Lost[30] | Scattered-disc object; a dwarf-planet candidate |
| 2007 WD5 | 2007 | Lost | Passed close to Mars |
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