The following is a list of unnumbered minor planets in chronological order of their principal provisional designation. Contrary to their numbered counterparts, unnumbered minor planets have a poorly determined orbit due to insufficient observational data. This also includes lost minor planets which have not been observed for many years, or even decades. As of August 2023[update], the Minor Planet Center (MPC) accounts for 676,755 unnumbered minor planets which represent 52% of the overall minor planet population.[1][a] Unnumbered minor planets can be further divided into 129,103 single-opposition objects with short observation arcs, prone to mismatch and loss, and 547,652 objects that have been observed multiple times during opposition, when astrometric conditions are most favorable.[1] The JPL Small-Body Database gives a running total of 676,786 unnumbered minor planets.[2][a]
The tables below contain 95 objects with a principal designation assigned between 1927 and 1993. Additional partial lists cover the period from 1994 to 2004.[a] Unnumbered minor planets detected after 2004 are not listed due to their large number (see statistics). The orbital uncertainty parameter (U) ranges from low ("0") to very high ("9"). For some single-opposition objects no numeric uncertainty is given ("–" and "E"), latter indicating an estimated, rather than determined orbital eccentricity. Furthermore, a color code is used to indicate a body's basic dynamical classification, with additional information given in columns "class" and "description and notes" (especially for near-Earth objects, Jupiter trojans and distant objects).[1][3][4] If available, mean diameters are taken from the latest NEOWISE publication,[5] or, if not available, estimated based on an object's absolute magnitude and displayed in italics.[6]
In the Minor Planet Circular from July 2018, the MPC announced that changes in their data processing pipeline will enable numberings to occur more frequently. It is stated that the new method will clear the backlog of unnumbered minor planets with an already well-established orbit without changing the criteria for numbering. Previously, this was not possible because of the difficulty of determining who was the discoverer.[7] Despite this announcement, however, the total of unnumbered minor planets has since significantly increased rather than decreased.
Statistics
10,000
20,000
30,000
40,000
50,000
60,000
70,000
1995
2000
2005
2010
2015
2020
Unnumbered minor planets (uMPs) by year of principal designation. As of 29 January 2022[update] the MPC's orbit database contains 558,491 uMPs. Objects observed on a single opposition (total of 111,001) are displayed with a lighter color than multi-opposition objects (total of 447,490).[1][a]
The year of principal provisional designation for most unnumbered minor planets is younger than 2004 (see § Statistics). They are not listed in any of the partial lists due to their large number and frequent changes. New partial lists may be created in the future, as additional observations ultimately lead to new numberings and to fewer unnumbered bodies.
^ abcdeThe data for this and other partial lists is sourced from the Minor Planet Center's orbit-database file (MPCORB.DAT). The number of entries typically differs from the summary figures published on the JPL and MPC web pages, as they may lag behind days, weeks, or even months. This includes MPC's "Latest Published Data" and "Archive Statistics – Orbits And Names".[8][9]
