More than 700,000 minor planets have been observed, many of which must be considered lost due to insufficient observational data.[1][2]

A minor planet is "lost" when today's observers cannot find it, because its location is too uncertain to target observations. This happens if the orbital elements of a minor planet are not known accurately enough, typically because the observation arc for the object is too short, or too few observations were made before the object became unobservable (e.g. too faint due to increasing distance, or too close to the Sun to view at night).

By some definitions thousands, if not tens of thousands, of mostly small observed minor planets are lost.[2] Some lost minor planets discovered in decades past cannot be found because the available observational data is insufficient for reliable orbit determination. With limited information astronomers cannot know where to look for the object at future dates.

Lost objects are sometimes recovered when serendipitously re-observed by a later astronomical survey. If the orbital elements of the newly found object are sufficiently close to those of the earlier lost object, the two may be equated. This can be established by calculating backwards the "new" object's orbit (once it is firmly known) and checking past positions against those previously recorded for the lost object. This usually greatly extends the object's arc length, thus fixing the orbit much more precisely. The back-orbit calculations are especially tricky for lost comets because their orbits can be affected by non-gravitational forces, such as emission of jets of gas from the comet nucleus. Many previously lost asteroids (a type of minor planet) were rediscovered in the 1980s and 1990s, but many minor planets are still lost.[3]


The orbits of kilometre class NEAs are generally well known, though a few have been lost. However, large numbers of smaller NEAs have highly uncertain orbits[4]

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.[2] 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.[5][a] There are also more than a thousand near-Earth objects (NEOs) with an observation arc of one or two days only.[6]

Designation Year of
discovery recovery
132 Aethra 1873 1922[7]
1892 X (330 Adalberta) 1892 false positive[b]
452 Hamiltonia 1899 1981
473 Nolli 1901 1987
(12126) 1999 RM11
(A904 RD)
1904 1999
719 Albert 1911 2000
724 Hapag 1911 1988
843 Nicolaia 1916 1981
878 Mildred 1916 1991
1009 Sirene 1923 1982[8]
1026 Ingrid 1923 1986
Name Year of
discovery recovery
3789 Zhongguo 1928 1986
1179 Mally 1931 1986
1862 Apollo 1932 1973
2101 Adonis 1936 1977
69230 Hermes 1937 2003[9][10]
1537 Transylvania 1940 1981
1922 Zulu 1949 1974
(29075) 1950 DA 1950 2000
1916 Boreas 1953[9] 1976
3494 Purple Mountain 1962 1980
7796 Járacimrman 1973 1996
Designation Year of Notes MPC
discovery recovery
1927 LA [11] 1927 false positive[12] Observed 3 times between 1 June 1927 and 5 July 1927 MPC
1991 BA 1991 still lost Passed within a lunar distance of Earth MPC
1995 SN55 1995 2020 3:5 resonant TNO initially thought to be a large centaur MPC
2007 WD5 2007 still lost Passed close to Mars MPC
6344 P-L 1960 2007[13] Potentially hazardous object; probably a dormant comet MPC

20th-century recoveries

The number of asteroids that were only observed once and not re-observed grew throughout the 19th and 20th centuries, but improved telescopes, searches, and detection techniques led to resolution of most of these cases between 1970 and 2000. There are earlier examples also, such as 132 Aethra, which was lost between 1873 and 1922.[7]


Recovered body Description
1862 Apollo 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 The Amor asteroid Boreas, provisionally designated 1953 RA, was discovered on 1 September 1953 by Sylvain Julien Victor Arend at the Royal Observatory of Belgium, and rediscovered in 1974 by Richard Eugene McCrosky, G. Schwartz and JH Bulger based on a predicted position by Brian G. Marsden.[9][14]
1922 Zulu The outer main-belt asteroid, provisionally designated 1949 HC, was discovered on 25 April 1949 by Ernest Leonard Johnson at Johannesburg (UO).[9] It is one of very few asteroids located in the 2:1 mean-motion resonance with Jupiter.[15] 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.[9][14]

1980s and 1990s

Leif Kahl Kristensen at the University of Aarhus rediscovered 452 Hamiltonia and 1537 Transylvania, along with numerous other small objects, in 1981.[16] At the time these results were published, only the nine numbered minor planets 330 Adalberta, 473 Nolli, 719 Albert, 724 Hapag, 843 Nicolaia, 878 Mildred, 1009 Sirene, 1026 Ingrid, and 1179 Mally (below) had remained unobserved since their discoveries:[16]

Recovered body Description
330 Adalberta The object originally named Adalberta, provisionally designated 1892 X, turned out to be an erroneous observation. The designation was later reassigned to A910 CB.[17]
843 Nicolaia Nicolaia, provisionally designated 1916 AN, was rediscovered at the Heidelberg Astronomisches Rechen-Institut in 1981.[18]
473 Nolli Nolli, provisionally designated 1901 GC, was discovered by Max Wolf on 13 February 1901, but it remained lost for many decades until it was recovered finally in 1987, 86 years later.[19]
724 Hapag Hapag had first been found by Johann Palisa in 1911. It was given the provisional name 1911 NC, but was lost until it was rediscovered in 1988.[20][21]
719 Albert Near-Earth asteroid 719 Albert (1911 MT) had also been found by Johann Palisa in 1911. 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. At the time of its rediscovery, Albert was the last remaining "lost asteroid" among those assigned numbers (since 69230 Hermes was not numbered until 2003).[21]
878 Mildred Mildred, provisionally designated 1916 f, was originally discovered in 1916 using the 60-inch Hale telescope at the Californian Mount Wilson Observatory, but was subsequently lost until it was again observed on single nights in 1985 and 1991.[21][22]
1009 Sirene Sirene, provisionally designated 1923 PE, was recovered in 1982 by J. Gibson using exposures form the Samuel Oschin Telescope at Palomar Observatory, and he revised its ephemeris.[8]
1026 Ingrid Ingrid was discovered by Karl Reinmuth on 13 August 1923 and given the provisional designation 1923 NY.[9] It was reidentified in 1986 by Syuichi Nakano.[23]
1179 Mally Mally was discovered by Max Wolf on 19 March 1931 and given the provisional designation 1931 FD.[9] It was rediscovered in 1986 by Lutz Schmadel, Richard Martin West and Hans-Emil Schuster.[24]

Other notable recoveries

21st century

Recently lost minor planets

See also


  1. ^ Note: this query at JPL's Small-Body Database lists all unnamed asteroids with an orbital uncertainty of 9, which also includes recently discovered bodies. The lost minor planets appear first, since the table is sorted by the body's first observation date.
  2. ^ On 18 March 1892, a body discovered by Max Wolf with the provisional designation 1892 X was originally named 330 Adalberta, but was lost and never recovered. In 1982, it was determined that Wolf erroneously measured two images of stars, not asteroids. Because it was a false positive and the body never existed, the named designation 330 Adalberta was reused for another asteroid, A910 CB, discovered in 1910.


  1. ^ "Running Tallies – Minor Planets Discovered". IAU Minor Planet Center. Retrieved 19 August 2015.
  2. ^ a b c Blair, Edward C. (2002). Asteroids: overview, abstracts, and bibliography (2002), by Edward C. Blair, Page 177. ISBN 9781590334829. Retrieved 23 July 2013.
  3. ^ Lost asteroid. (2009). In Encyclopædia Britannica. Retrieved 27 February 2009, from Encyclopædia Britannica Online:
  4. ^ "Orbits for Near Earth Asteroids (NEAs)". IAU Minor Planet Center. International Astronomical Union. Retrieved 25 June 2020.
  5. ^ "JPL Small-Body Database Search Engine: Unnumbered asteroids with condition code of 9, oldest first obs. shown first". JPL Solar System Dynamics. Retrieved 24 May 2016.
  6. ^ "JPL Small-Body Database Search Engine: NEOs with observation arc of 1 or 2 days only". JPL Small-Body Database. Retrieved 24 May 2016.
  7. ^ a b Price, Fred W. (26 October 2000). The planet observer's handbook (2000), By Fred William Price, Page 192. (Google Books 2010). ISBN 9780521789813. Retrieved 23 July 2013.
  8. ^ a b Gibson, J.; Kristensen, L. K. (22 July 1982). Marsden, B. G (ed.). "(1009) Sirene Gibson". IAU Circular. No. 3714. Central Bureau for Astronomical Telegrams. Bibcode:1982IAUC.3714....1G.
  9. ^ a b c d e f g "Discovery Circumstances: Numbered Minor Planets (1)–(5000)". IAU: Minor Planet Center. Retrieved 5 July 2011.
  10. ^ "MPEC 2003-T74: 1937 UB (HERMES)". Retrieved 23 July 2013.
  11. ^ "1927 LA". Minor Planet Center. Retrieved 24 May 2016.
  12. ^ Meyer, Maik (2 March 2022). "Re: Identification of old discoveries". Retrieved 30 March 2022.
  13. ^ a b "Long-Lost, Dangerous Asteroid Is Found Again – ScienceDaily (15 Oct. 2007)". 15 October 2007. Retrieved 18 August 2015.
  14. ^ a b Brian G. Marsden (24 October 1974). "International Astronomical Union Circular 2710". Central Bureau for Astronomical Telegrams. Retrieved 5 July 2011.
  15. ^ Roig; Nesvorny, D.; Ferraz-Mello, S. (2002). "Asteroids in the 2 : 1 resonance with Jupiter: dynamics and size distribution". Monthly Notices of the Royal Astronomical Society. 335 (2): 417–431. Bibcode:2002MNRAS.335..417R. doi:10.1046/j.1365-8711.2002.05635.x.
  16. ^ a b Kristensen, L. K.; Gibson, J.; Shao, C.-Y.; Bowell, E.; Marsden, B. G. (April 1981). "(1537) Transylvania and (452) Hamiltonia". IAU Circ. 3595 (3595): 1. Bibcode:1981IAUC.3595....1K. Retrieved 24 May 2016.
  17. ^ "JPL Small-Body Database Browser: 330 Adalberta (A910 CB)" (2016-04-17 last obs.). Jet Propulsion Laboratory. Retrieved 24 May 2016.
  18. ^ Wiley Interscience Recovery of the Long Lost Minor Planet (843) Nicolaia after 65 Years (Astronomisches Rechen-Institut Heidelberg – Mitteilungen Serie B) L. D. Schmadel 1 *, L. Kohoutek 2 * Heidelberg Astronomisches Rechen-Institut
  19. ^ IAUC 4292
  20. ^ Schmadel, Lutz D. (1997). Dictionary of Minor Planet Names. Springer Science+Business Media. p. 70. ISBN 978-0-354-06174-2. Archived from the original on 30 March 2009.
  21. ^ a b c Cowen, Ron (20 May 2000). "Astronomers Rediscover Long-Lost Asteroid". Science News. Vol. 157, no. 21. Archived from the original on 28 December 2012.
  22. ^ "(878) MILDRED". IAU Circular. No. 5275. 25 May 1991.
  23. ^ Brian G. Marsden (8 December 1986). "International Astronomical Union Circular 4281". Central Bureau for Astronomical Telegrams. Retrieved 5 July 2011.
  24. ^ Brian G. Marsden (5 December 1986). "International Astronomical Union Circular 4278". Central Bureau for Astronomical Telegrams. Retrieved 5 July 2011.
  25. ^ Schmadel, Lutz D. (2007). "(3789) Zhongguo". Dictionary of Minor Planet Names – (3789) Zhongguo. Springer Berlin Heidelberg. p. 320. doi:10.1007/978-3-540-29925-7_3783. ISBN 978-3-540-00238-3.
  26. ^ "Earth Impact Risk Summary: 29075 1950 DA". NASA/JPL Near-Earth Object Program Office. 26 November 2013. Archived from the original on 26 December 2013. Retrieved 23 June 2014.
  27. ^ "JPL Small-Body Database Browser: 2007 WD5". Retrieved 12 January 2008.
  28. ^ a b Don Yeomans, Paul Chodas and Steve Chesley (28 December 2007). "Mars Impact Probability Increases to 4 Percent". NASA/JPL Near-Earth Object Program Office. Archived from the original on 29 December 2007. Retrieved 28 December 2007.
  29. ^ a b Steve Chesley, Paul Chodas and Don Yeomans (9 January 2008). "2007 WD5 Mars Collision Effectively Ruled Out – Impact Odds now 1 in 10,000". NASA/JPL Near-Earth Object Program Office. Archived from the original on 11 January 2008. Retrieved 9 January 2008.
  30. ^ Lakdawalla, Emily (4 February 2008). "WD5 most likely missed Mars, but we may never know". Retrieved 24 February 2008.
  31. ^ "Horizons Archive Mars/Earth 2003/2008". Archived from the original on 13 August 2007. Retrieved 23 December 2007. ( 2007-Dec-23)
  32. ^ "JPL Small-Body Database Browser: (2010 AU118)" (last observation: 2010-01-15; arc: 2 days). Jet Propulsion Laboratory. Archived from the original on 13 December 2012. Retrieved 13 May 2020.
  33. ^ "Earth Impact Risk Summary: 2010 AU118". NASA/JPL Near-Earth Object Program Office. Archived from the original on 3 April 2014. Retrieved 13 May 2020.
  34. ^ "2010AU118 Ephemerides for 20 October 2020". NEODyS (Near Earth Objects – Dynamic Site). Retrieved 13 May 2020.