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NEO Discovery Statistics

NEAR-EARTH ASTEROID DISCOVERY STATISTICS

Some entries in the following charts and tables are dependent upon a diameter that is roughly inferred from the object’s estimated absolute magnitude (H) and its assumed reflectivity, or albedo. The absolute magnitude (H) of a near-Earth asteroid (NEA) is a measure of the object's brightness one astronomical unit from the sun and Earth and at zero phase angle (i.e., the angle between the sun and Earth, as seen from the NEA, is zero). The absolute magnitude (H) for a particular NEA is computed from the observed apparent magnitudes of the object at various times when the phase angles and the distances from the sun and Earth are known. An effective diameter is the diameter of a hypothetical spherical NEA that would provide the same apparent brightness as the observed NEA, whose actual shape is unknown.

Since most NEAs do not have a known reflectivity, or albedo, this albedo must be estimated before the H values, representing intrinsic brightness, can be converted to an approximate diameter. Pravec et al (2012) determined that, for their sample of 583 main-belt asteroids and NEAs, the mean albedos and their standard deviations are 0.057 (±0.013) for the Tholen/Bus/DeMeo C/G/B/F/P/D types and 0.197 (±0.051) for the S/A/L types. Since the albedos for NEAs are most likely to be either approximately 6% for asteroids of the C-type and associated taxonomic classes or 20% for asteroids of the more populous S-type and associated taxonomic classes, we have used an approximate mean value of 14% albedo and an H value of 17.75 to represent a one kilometer spherical NEA. Since the determined H values are uncertain, and likely biased by a few tenths (see Pravec et al., 2012, Icarus) and the single 14% albedo is only a rough mean representing a bimodal albedo distribution, the estimated numbers of one kilometer and larger sized objects in the tables below are very rough. However, these statistics are useful for monitoring the annual NEA discovery progress.

Using near-infrared data provided by the WISE spacecraft in 2010 and early 2011, Mainzer et al (2011) were able to determine diameters and albedos for 250 NEAs with a minimum uncertainty of 10% and 20% respectively. Hence they were able to determine the albedo distribution of these objects with known diameters and this distribution was then used to compute diameters for previously known NEOs with known H values but unknown diameters or albedos. They provided an estimate of 981 (±19) NEAs as the total population of NEAs one kilometer and larger. At the time of their analysis (Spring 2011), they also estimated that 911 (±17) of these large NEAs had already been discovered. While this latter estimate is both higher and more accurate than the estimated numbers given for Spring 2011 in the following tables, this statistical technique cannot be easily employed for day-to-day estimates of the population of NEAs one kilometer and larger. In the following tables, we will continue to use the simpler method described in the previous paragraph.

Mainzer, A. et al. (2011). NEOWISE observations of near-Earth objects: Preliminary Results. Astrophysical Journal. 743:156.
Pravec, P., A.W. Harris, P. Kusnirak, A. Galad, K. Hornoch (2012). Absolute magnitudes of asteroids and a revision of asteroid albedo estimates from WISE thermal observations. Icarus (submitted 6/2012).
Stuart, J.S. (2003). Observational constraints on the number, albedos, sizes and impact hazards of the near-Earth asteroids. Ph.D. thesis, MIT.

All Asteroids

Table: Number of Near-Earth Asteroid Discoveries at Half-Year Intervals: All Asteroids

Table 1. NEAs Discovered by Site

Half Year
Intervals
LINEAR
(704)
NEAT
(566,608,644)
Spacewatch
(691,291)
LONEOS
(699)
Catalina
(703,E12,G96)
Pan-STARRS
(F51)
NEOWISE
(C51)
OtherCumulative
Total
 1995 (1)001400004334
 1995 (2)001201002349
 1996 (1)151800004377
 1996 (2)051000002394
 1997 (1)321000004413
 1997 (2)149400007447
 1998 (1)4491911007528
 1998 (2)9221562005650
 1999 (1)75012611001755
 1999 (2)8707719003878
 2000 (1)10821421130041040
 2000 (2)15014121700081241
 2001 (1)942872200021394
 2001 (2)18364152000041680
 2002 (1)15856161410061931
 2002 (2)130896700052168
 2003 (1)10230233300092365
 2003 (2)13338332170082605
 2004 (1)167194114250062877
 2004 (2)13772925600063141
 2005 (1)778292211500103402
 2005 (2)5930541919300103767
 2006 (1)44445131950034071
 2006 (2)52175461990054404
 2007 (1)3842072010034677
 2007 (2)7402552660075054
 2008 (1)7404312810055458
 2008 (2)66043028000115858
 2009 (1)51032026000186219
 2009 (2)58031031500176640
 2010 (1)29021025708797043
 2010 (2)7502203461737147554
 2011 (1)410170328683128023
 2011 (2)2901502521040238446
 2012 (1)260130352120078964
 2012 (2)2901302771310269440
 2013 (1)301302881500189912
 2013 (2)0012031520812910477
 2014 (1)00803322411614511219
 2014 (2)0080285382243811956
 2015 (1)*001035773312075
* Incomplete half-year (based on discovery data through 2015-Jan-28 06:05 local)

Large Asteroids

Table: Number of Near-Earth Asteroid Discoveries at Half-Year Intervals: Large Asteroids

Table 2. Large NEAs Discovered by Site

Half Year
Intervals
LINEAR
(704)
NEAT
(566,608,644)
Spacewatch
(691,291)
LONEOS
(699)
Catalina
(703,E12,G96)
Pan-STARRS
(F51)
NEOWISE
(C51)
OtherCumulative
Total
 1995 (1)00300002177
 1995 (2)00400001182
 1996 (1)02200000186
 1996 (2)02000000188
 1997 (1)01300001193
 1997 (2)23100002201
 1998 (1)74210002217
 1998 (2)242130003250
 1999 (1)160244000276
 1999 (2)230112002305
 2000 (1)332114001347
 2000 (2)372350004398
 2001 (1)238040000433
 2001 (2)225040001465
 2002 (1)294230001504
 2002 (2)1911010001536
 2003 (1)143260002563
 2003 (2)175142001593
 2004 (1)155123001620
 2004 (2)910112000643
 2005 (1)100219001666
 2005 (2)645010001692
 2006 (1)30219000707
 2006 (2)102012000722
 2007 (1)20309001737
 2007 (2)50107000750
 2008 (1)20109000762
 2008 (2)30104000770
 2009 (1)10009000780
 2009 (2)60006002794
 2010 (1)00004030801
 2010 (2)10002030807
 2011 (1)20005100815
 2011 (2)00106300825
 2012 (1)00009100835
 2012 (2)10005200843
 2013 (1)00004000847
 2013 (2)00003201853
 2014 (1)00002420861
 2014 (2)00001310866
 2015 (1)*00100200869
* Incomplete half-year (based on discovery data through 2015-Jan-28 06:05 local)
NOTE: In the year 2010, the "Other" site category was exclusively WISE.
A separate table of WISE discoveries is
available.

Data compiled by Alan Chamberlin.

NUMBER OF NEOS
With over 90% of the near-Earth objects larger than one kilometer already discovered, the NEO Program is now focusing on finding 90% of the NEO population larger than 140 meters. A separate table containing WISE discoveries for NEAs and comets is available.

The chart below shows the cumulative total known near-Earth asteroids versus time. The blue area shows all near-Earth asteroids while the red area shows only large near-Earth asteroids (those with diameters roughly one kilometer and larger).
Table: Number of Known Near-Earth Asteroids Over Time
(click on the chart above for a larger version)

The chart below shows the total known near-Earth asteroids per size bin. Diameters are estimated using an assumed average albedo for NEAs. The first size bin represents NEAs smaller than 30m in diameter. The second represents NEAs with diameters from 30m to 100m, and so on.
Known Near-Earth Asteroids by Size Bin
Data shown in the chart above represent known NEAs as of the date shown in the bottom-right corner of the chart.

The table below shows the total number of NEOs known at selected dates. The most recent date at the top of the table is generally not the date the table was updated, but rather the discovery date of the most recently discovered NEO. Numbers for large asteroids (PHA-KM and NEA-KM) are rough estimates (see introductory note above). This table is updated daily using discovery data published by the Minor Planet Center.

----------------------------------------------------------------------------
   Date      NEC  Atira  Aten Apollo  Amor  PHA-KM  PHA  NEA-KM  NEA    NEO
----------  ----  ----- ----- ------ -----  ------ ----  ------ -----  -----
2015-01-25    96     14   896   6516  4649     154 1544     869 12075  12171
2015-01-01    95     14   889   6451  4602     154 1533     866 11956  12051
2014-12-01    95     14   880   6386  4565     154 1524     864 11845  11940
2014-11-01    95     14   874   6311  4502     154 1515     861 11701  11796
2014-10-01    94     14   867   6221  4439     154 1510     861 11541  11635
2014-09-01    94     14   861   6168  4384     154 1504     861 11427  11521
2014-08-01    94     14   856   6115  4311     154 1495     861 11296  11390
2014-07-01    94     14   854   6072  4279     154 1485     861 11219  11313
2014-06-01    94     14   845   6035  4222     153 1477     857 11116  11210
2014-05-01    94     14   838   5968  4175     153 1465     855 10995  11089
2014-04-01    94     14   826   5852  4067     153 1456     854 10759  10853
2014-03-01    94     13   819   5796  4040     153 1451     854 10668  10762
2014-02-01    94     13   811   5751  4002     153 1444     854 10577  10671
2014-01-01    94     13   804   5698  3962     153 1440     853 10477  10571
2013-12-01    94     13   799   5643  3936     153 1436     853 10391  10485
2013-11-01    94     13   798   5572  3909     153 1428     853 10292  10386
2013-10-01    94     12   786   5513  3847     152 1420     849 10158  10252
2013-09-01    94     12   780   5456  3792     152 1416     848 10040  10134
2013-08-01    94     12   778   5425  3755     152 1410     848  9970  10064
2013-07-01    94     12   773   5397  3730     152 1403     847  9912  10006
2013-06-01    94     12   770   5367  3712     152 1397     845  9861   9955
2013-05-01    94     11   765   5327  3692     152 1390     845  9795   9889
2013-04-01    94     11   760   5286  3661     152 1381     844  9718   9812
2013-03-01    94     11   755   5238  3633     152 1372     844  9637   9731
2013-02-01    93     11   750   5199  3606     152 1368     844  9566   9659
2013-01-01    93     11   743   5118  3568     152 1354     843  9440   9533
2012-12-01    93     11   735   5065  3537     152 1343     843  9348   9441
2012-11-01    92     10   727   5011  3500     152 1334     840  9248   9340
2012-10-01    92     10   721   4936  3444     152 1323     838  9111   9203
2012-09-01    92     10   717   4903  3414     152 1320     837  9044   9136
2012-08-01    92     10   712   4878  3380     152 1315     836  8980   9072
2012-07-01    91     10   711   4872  3371     152 1311     835  8964   9055
2012-06-01    91     10   706   4846  3348     152 1302     832  8910   9001
2012-05-01    91     10   704   4813  3324     152 1297     829  8851   8942
2012-04-01    91     10   702   4762  3297     152 1291     828  8771   8862
2012-03-01    91     10   696   4682  3270     152 1285     826  8658   8749
2012-02-01    91     10   686   4635  3229     152 1279     826  8560   8651
2012-01-01    91     10   676   4566  3194     152 1271     825  8446   8537
2011-12-01    91     10   672   4534  3169     152 1264     821  8385   8476
2011-11-01    91     10   669   4493  3135     150 1254     818  8307   8398
2011-10-01    91     10   662   4431  3090     149 1243     817  8193   8284
2011-09-01    90     10   661   4396  3037     149 1237     816  8104   8194
2011-08-01    90     10   661   4380  3011     149 1234     815  8062   8152
2011-07-01    89     10   659   4367  2987     149 1230     815  8023   8112
2011-06-01    89     10   659   4350  2962     149 1224     814  7981   8070
2011-05-01    89     10   656   4324  2939     149 1216     812  7929   8018
2011-04-01    89     10   645   4275  2910     149 1209     810  7840   7929
2011-03-01    89     10   634   4212  2886     149 1200     808  7742   7831
2011-02-01    89     10   624   4166  2868     149 1189     808  7668   7757
2011-01-01    89     10   618   4091  2835     149 1173     807  7554   7643
2010-12-01    89      9   609   4036  2804     149 1164     807  7458   7547
2010-11-01    89      9   598   3967  2758     149 1158     807  7332   7421
2010-10-01    89      9   588   3911  2719     149 1144     807  7227   7316
2010-09-01    89      9   582   3864  2654     149 1139     805  7109   7198
2010-08-01    89      9   579   3850  2643     149 1136     802  7081   7170
2010-07-01    89      9   574   3828  2632     149 1134     801  7043   7132
2010-06-01    88      9   568   3797  2610     149 1126     800  6984   7072
2010-05-01    87      9   560   3753  2591     148 1114     798  6913   7000
2010-04-01    87      9   552   3707  2574     148 1108     798  6842   6929
2010-03-01    87      9   544   3670  2549     147 1099     797  6772   6859
2010-02-01    87      9   540   3616  2524     147 1087     796  6689   6776
2010-01-01    87      9   535   3590  2506     147 1084     794  6640   6727
2009-12-01    87      9   531   3569  2496     147 1079     792  6605   6692
2009-11-01    86      9   520   3493  2467     147 1071     789  6489   6575
2009-10-01    86      9   511   3438  2434     147 1067     787  6392   6478
2009-09-01    86      9   506   3385  2387     147 1058     785  6287   6373
2009-08-01    86      9   504   3365  2360     147 1056     784  6238   6324
2009-07-01    86      9   504   3355  2351     146 1054     780  6219   6305
2009-06-01    85      9   501   3344  2340     145 1051     779  6194   6279
2009-05-01    85      9   499   3317  2326     145 1042     778  6151   6236
2009-04-01    85      9   496   3285  2312     145 1038     775  6102   6187
2009-03-01    85      9   491   3224  2293     145 1026     775  6017   6102
2009-02-01    85      9   487   3165  2267     144 1014     772  5928   6013
2009-01-01    85      9   481   3121  2247     144 1005     770  5858   5943
2008-12-01    84      9   480   3079  2218     144  995     769  5786   5870
2008-11-01    84      9   474   3031  2196     144  987     767  5710   5794
2008-10-01    84      8   467   2969  2145     143  977     766  5589   5673
2008-09-01    83      8   464   2938  2110     143  967     765  5520   5603
2008-08-01    83      8   461   2924  2096     143  962     764  5489   5572
2008-07-01    83      8   459   2907  2084     143  953     762  5458   5541
2008-06-01    83      8   455   2896  2076     143  950     761  5435   5518
2008-05-01    83      8   451   2866  2058     143  944     760  5383   5466
2008-04-01    83      8   449   2819  2029     143  941     759  5305   5388
2008-03-01    83      7   440   2751  2004     142  931     752  5202   5285
2008-02-01    83      7   428   2691  1974     141  917     750  5100   5183
2008-01-01    83      7   426   2664  1957     141  909     750  5054   5137
2007-12-01    83      7   423   2629  1940     141  898     747  4999   5082
2007-11-01    83      7   411   2571  1904     141  888     743  4893   4976
2007-10-01    82      7   397   2522  1862     141  877     742  4788   4870
2007-09-01    82      7   390   2484  1830     140  870     741  4711   4793
2007-08-01    82      7   388   2473  1820     139  865     737  4688   4770
2007-07-01    82      7   388   2469  1813     139  864     737  4677   4759
2007-06-01    82      7   383   2447  1804     138  855     735  4641   4723
2007-05-01    82      7   382   2434  1793     138  851     733  4616   4698
2007-04-01    82      7   381   2408  1776     138  847     729  4572   4654
2007-03-01    82      6   375   2368  1753     138  840     727  4502   4584
2007-02-01    82      6   367   2335  1737     137  832     723  4445   4527
2007-01-01    82      6   359   2315  1724     137  823     722  4404   4486
2006-12-01    81      6   354   2289  1706     137  820     720  4355   4436
2006-11-01    81      5   344   2240  1683     136  808     714  4272   4353
2006-10-01    79      5   337   2210  1651     136  798     712  4203   4282
2006-09-01    79      5   330   2173  1624     135  789     708  4132   4211
2006-08-01    79      5   328   2156  1611     135  784     708  4100   4179
2006-07-01    79      5   327   2145  1594     135  782     707  4071   4150
2006-06-01    79      5   326   2134  1581     135  779     707  4046   4125
2006-05-01    79      5   325   2106  1554     135  769     703  3990   4069
2006-04-01    78      5   321   2079  1539     135  760     701  3944   4022
2006-03-01    78      5   319   2064  1520     135  759     700  3908   3986
2006-02-01    78      5   316   2029  1503     135  751     697  3853   3931
2006-01-01    78      5   312   1974  1476     134  742     692  3767   3845
2005-12-01    78      5   302   1942  1455     133  731     689  3704   3782
2005-11-01    77      5   297   1900  1429     132  721     684  3631   3708
2005-10-01    76      4   289   1844  1389     131  709     673  3526   3602
2005-09-01    76      4   286   1810  1370     131  704     670  3470   3546
2005-08-01    76      4   283   1796  1354     131  698     669  3437   3513
2005-07-01    76      4   279   1777  1342     130  691     666  3402   3478
2005-06-01    76      4   275   1762  1322     130  687     661  3363   3439
2005-05-01    75      4   274   1745  1308     128  681     658  3331   3406
2005-04-01    75      4   268   1720  1290     126  668     654  3282   3357
2005-03-01    75      4   263   1680  1264     125  658     650  3211   3286
2005-02-01    75      4   262   1657  1256     124  654     647  3179   3254
2005-01-01    75      4   258   1633  1246     124  647     643  3141   3216
2004-12-01    74      3   249   1601  1225     124  639     635  3078   3152
2004-11-01    74      3   245   1581  1219     123  630     630  3048   3122
2004-10-01    73      3   238   1553  1211     122  619     628  3005   3078
2004-09-01    72      3   230   1515  1186     122  611     627  2934   3006
2004-08-01    72      3   226   1495  1164     121  604     623  2888   2960
2004-07-01    72      3   226   1488  1160     119  601     620  2877   2949
2004-06-01    72      3   223   1458  1147     118  590     617  2831   2903
2004-05-01    72      2   218   1439  1132     118  584     613  2791   2863
2004-04-01    72      2   215   1409  1120     114  574     606  2746   2818
2004-03-01    72      2   206   1373  1102     114  567     597  2683   2755
2004-02-01    71      2   204   1358  1095     113  562     596  2659   2730
2004-01-01    71      2   202   1324  1077     111  552     593  2605   2676
2003-12-01    71      2   196   1292  1065     108  539     585  2555   2626
2003-11-01    71      2   193   1271  1052     108  532     579  2518   2589
2003-10-01    70      2   188   1244  1030     108  523     577  2464   2534
2003-09-01    70      2   185   1224   996     106  514     570  2407   2477
2003-08-01    70      2   185   1212   983     103  509     566  2382   2452
2003-07-01    69      2   184   1205   974     103  506     563  2365   2434
2003-06-01    69      2   182   1189   962     103  501     557  2335   2404
2003-05-01    67      2   180   1175   956     102  499     555  2313   2380
2003-04-01    67      2   175   1155   945     101  491     549  2277   2344
2003-03-01    67      2   170   1136   934     101  484     545  2242   2309
2003-02-01    67      1   169   1116   928     101  478     541  2214   2281
2003-01-01    67      1   167   1089   911     100  468     536  2168   2235
2002-12-01    67      1   163   1062   891     100  466     534  2117   2184
2002-11-01    67      1   160   1047   874      99  460     530  2082   2149
2002-10-01    66      1   158   1023   851      98  454     522  2033   2099
2002-09-01    64      1   155   1003   831      97  448     513  1990   2054
2002-08-01    64      1   154    987   808      95  437     510  1950   2014
2002-07-01    63      1   152    977   801      94  430     504  1931   1994
2002-06-01    63      1   148    960   792      92  422     498  1901   1964
2002-05-01    63      1   144    942   781      91  413     487  1868   1931
2002-04-01    63      1   142    924   768      91  406     485  1835   1898
2002-03-01    62      1   136    897   754      90  396     482  1788   1850
2002-02-01    62      1   131    874   738      89  387     472  1744   1806
2002-01-01    62      1   124    840   715      89  374     465  1680   1742
2001-12-01    62      1   121    804   696      85  360     456  1622   1684
2001-11-01    60      1   120    776   681      84  353     452  1578   1638
2001-10-01    60      1   114    751   657      83  344     448  1523   1583
2001-09-01    60      1   110    722   623      82  333     437  1456   1516
2001-08-01    59      1   109    700   603      82  327     434  1413   1472
2001-07-01    58      1   108    695   590      82  326     433  1394   1452
2001-06-01    57      1   108    685   580      80  323     426  1374   1431
2001-05-01    56      1   107    673   569      78  316     418  1350   1406
2001-04-01    56      1   105    661   560      77  307     414  1327   1383
2001-03-01    56      1   101    646   546      75  298     407  1294   1350
2001-02-01    56      1    98    635   535      74  295     402  1269   1325
2001-01-01    56      1    94    620   526      74  292     398  1241   1297
2000-12-01    56      1    93    606   514      73  286     391  1214   1270
2000-11-01    56      1    90    582   497      72  283     382  1170   1226
2000-10-01    56      1    87    572   483      72  279     375  1143   1199
2000-09-01    56      1    81    554   457      71  272     367  1093   1149
2000-08-01    56      1    79    536   441      69  263     358  1057   1113
2000-07-01    56      1    77    531   431      67  260     347  1040   1096
2000-06-01    56      1    76    526   425      66  256     344  1028   1084
2000-05-01    56      1    76    513   411      66  251     336  1001   1057
2000-04-01    55      1    73    498   398      65  245     329   970   1025
2000-03-01    55      1    64    482   387      63  233     317   934    989
2000-02-01    55      1    62    465   376      62  222     310   904    959
2000-01-01    55      1    57    451   369      62  216     305   878    933
1999-12-01    54      1    56    441   360      60  208     298   858    912
1999-11-01    54      1    54    428   346      60  204     288   829    883
1999-10-01    54      1    54    412   332      59  199     284   799    853
1999-09-01    52      1    54    396   316      57  192     280   767    819
1999-08-01    52      1    54    396   314      57  192     280   765    817
1999-07-01    52      1    54    391   309      56  190     276   755    807
1999-06-01    52      1    51    384   299      56  186     273   735    787
1999-05-01    51      1    49    372   293      52  178     263   715    766
1999-04-01    51      1    48    359   286      51  174     256   694    745
1999-03-01    51      1    47    349   281      51  172     255   678    729
1999-02-01    51      1    47    339   276      51  169     252   663    714
1999-01-01    51      1    45    334   270      51  166     250   650    701
1998-12-01    51      1    41    324   261      51  162     241   627    678
1998-11-01    51      1    38    310   252      49  154     236   601    652
1998-10-01    51      1    36    306   245      49  152     232   588    639
1998-09-01    51      1    29    293   232      48  140     226   555    606
1998-08-01    51      1    29    283   221      46  133     220   534    585
1998-07-01    51      1    29    279   219      44  129     217   528    579
1998-06-01    51      1    29    273   212      43  127     214   515    566
1998-05-01    51      1    29    264   206      43  124     210   500    551
1998-04-01    51      1    27    256   197      43  117     209   481    532
1998-03-01    51      1    27    244   189      43  112     205   461    512
1998-02-01    51      0    26    240   189      42  110     204   455    506
1998-01-01    51      0    26    235   186      42  108     201   447    498
1997-01-01    51      0    22    206   166      40   97     188   394    445
1996-01-01    51      0    20    178   151      38   86     182   349    400
1995-01-01    51      0    19    163   134      37   83     172   316    367
1994-01-01    49      0    15    140   114      33   70     154   269    318
1993-01-01    49      0    13    117    98      31   64     140   228    277
1992-01-01    49      0    11    103    84      29   61     123   198    247
1991-01-01    47      0     9     76    73      24   49     105   158    205
1990-01-01    47      0     8     63    62      20   42      89   133    180
1980-01-01    43      0     3     27    22      12   17      44    52     95
1970-01-01    41      0     0     13    14       8   10      24    27     68
1960-01-01    40      0     0     10    10       7    8      18    20     60
1950-01-01    40      0     0      7     6       4    5      12    13     53
1940-01-01    35      0     0      3     6       2    3       8     9     44
1930-01-01    33      0     0      0     5       0    0       5     5     38
1920-01-01    31      0     0      0     3       0    0       3     3     34
1910-01-01    29      0     0      0     1       0    0       1     1     30
1900-01-01    27      0     0      0     1       0    0       1     1     28

Note: "NEC" are Near-Earth comets. "PHA-KM" and "NEA-KM" are PHAs and NEAs with diameters roughly one kilometer and larger. Other definitions, such as Apollo, are on the NEO groups page.

Data compiled by Alan Chamberlin.

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