This is a list of slow rotators—minor planets that have an exceptionally long rotation period. This period, typically given in hours, and sometimes called rotation rate or spin rate, is a fundamental standard physical property for minor planets. In recent years, the periods of many thousands of bodies have been obtained from photometric and, to a lesser extent, radiometric observations.
The periods given in this list are sourced from the Light Curve Data Base (LCDB), which contains lightcurve data for more than 15,000 bodies. Most minor planets have rotation periods between 2 and 20 hours. , a group of approximately 650 bodies, typically measuring 1–20 kilometers in diameter, have periods of more than 100 hours or 4 days. Among the slowest rotators, there are currently 15 bodies with a period longer than 1000 hours. According to the Minor Planet Center, the sharp lower limit of approximately 2.2 hours is due to the fact that most smaller bodies are thought to be rubble piles – conglomerations of smaller pieces, loosely coalesced under the influence of gravity – that fly apart if the period is shorter than this limit. The few minor planets rotating faster than 2.2 hours, therefore, can not be merely held together by self-gravity, but must be formed of a contiguous solid.
Potentially slow rotators have only an inaccurate period, estimated based on a fragmentary lightcurve and inconclusive measurement. They are listed separately from the more precise periods, which have a LCDB quality code, U, of 2 or 3 (unambiguous result). The periods for potentially slow rotators may be completely wrong (U = 1), have no complete and conclusive result (U = n.a.), or large error margins of more than 30% (U = 2−). A trailing plus sign (+) or minus sign (–) indicate slightly better or worse quality, respectively, than the unsigned value.
As with orbital periods, a rotational period can be sidereal or synodic to describe a full rotation with respect to the fixed stars (sidereal) and Sun (synodic), respectively. In most cases, the periods given in this list are synodic, not sidereal. However, in most cases the difference between these two different measures is not significant. This is the case for all main-belt asteroids, which account for 97.5% of all minor planets.
Slowest rotators
This list contains the slowest-rotating minor planets with periods of at least 1000 hours, or 41 days. See for minor planets with an insufficiently accurate period—that is, a LCDB quality code of less than 2.
# Minor planet designation Rotation period(hours) Δmag Quality(U) Orbit or family Spectral type Diameter(km) Abs. mag(H) Refs 1880 0.60 2 NEO S 0.78 17.90 846 Lipperta 1641 0.30 2 Themis CBU: 52.41 10.26 2440 Educatio 1561 0.80 2 Flora S 6.51 13.10 2056 Nancy 1343 0.68 3− MBA S 10.30 12.30 912 Maritima 1332 0.18 3− MBA C 82.14 9.30 9165 Raup 1320 1.34 3− Hungaria S 4.62 13.60 1235 Schorria 1265 1.40 3 Hungaria CX: 5.04 13.10 1256 0.42 2 Eunomia S 3.40 14.65 1234.2 0.69 2 Vestian S 2.96 15.01 288 Glauke 1170 0.90 3 MBA S 32.24 10.00 1167.4 0.80 2 MBA C 5.34 15.09 496 Gryphia 1072 1.25 3 Flora S 15.47 11.61 4524 Barklajdetolli 1069 1.26 2 Flora S 7.13 12.90 2675 Tolkien 1060 0.75 2+ Flora S 9.85 12.20 1007.7 0.86 2 MBA S 1.54 16.43
Periods between 500 and 1000 hours # Minor planet designation Rotation period(hours) Δmag Quality(U) Orbit or family Spectral type Diameter(km) Abs. mag(H) Refs 990 0.55 2 Mars crosser S 3.92 14.40 975.1 0.74 2 Eos S 4.44 14.51 14436 Morishita 972.8 0.82 2 MBA S 3.49 14.65 967.3 0.58 2 Eunomia S 2.94 14.97 938.2 0.47 2 MBA S 2.36 15.50 9000 Hal 908 0.90 2+ Flora S 4.11 14.10 894 1.32 2 Phocaea S 3.49 14.50 3233 Krisbarons 888 1.44 2 Flora S 6.51 13.10 887 0.96 2+ Phocaea S 5.53 13.50 831 Stateira 861 0.64 3− Flora S 6.81 13.00 2974 Holden 856 0.70 2+ Flora S 6.21 13.20 850 1.00 2 NEO S 0.45 19.10 849.2 0.74 2 Vestian S 3.88 14.42 2672 Písek 831 0.90 2+ Eunomia S 9.60 12.40 12867 Joeloic 813 0.71 2+ Flora S 4.94 13.70 2862 Vavilov 800 0.40 2 Flora S 7.82 12.70 800 0.46 2 MBA S 4.61 15.02 8109 Danielwilliam 790 0.60 2 Phocaea S 3.17 14.71 784.5 0.38 2 MBA C 10.06 13.72 1663 van den Bos 740 0.80 3− Flora S 12.25 11.90 4902 Thessandrus 738 0.60 2 Jupiter trojan C 61.04 9.80 731.3 1.16 2 MBA S 4.45 14.12 35286 Takaoakihiro 724.1 0.93 2 Eunomia S 3.22 14.77 708 0.43 3− Phocaea S 6.06 13.30 700.1 0.68 2 Eos S 7.14 13.48 670.8 0.69 2 MBA C 3.65 15.91 1479 Inkeri 660 1.30 2+ MBA XFU 17.52 11.90 11774 Jerne 648.1 0.68 2 MBA C 8.09 14.19 7352 Hypsenor 648 0.30 3− Jupiter trojan C 58.29 9.90 1144 Oda 648 0.55 2+ Hilda D 57.65 9.90 646.7 0.62 2 MBA S 5.92 14.26 625 0.52 2+ MBA S 2.47 15.40 8054 Brentano 623.8 0.46 2 Flora S 3.25 14.61 601.9 0.86 2 Vestian S 2.39 15.47 19640 Ethanroth 600.3 0.62 2 MBA C 6.54 14.65 600 0.80 3 Hungaria E 2.20 14.90 587.8 0.61 2 Flora S 3.94 14.19 587 0.32 3− Mars crosser S 2.97 15.00 576 0.92 2 Hungaria E 1.36 16.25 3448 Narbut 570.4 0.39 2 Flora S 5.69 13.39 562 0.45 2 Jupiter trojan C 50.77 10.20 27810 Daveturner 546 0.43 2+ Hungaria E 3.35 14.30 1042 Amazone 540 0.25 2 MBA C 73.59 9.90 539.6 0.52 2 MBA C 4.04 15.70 535.1 0.66 2 MBA C 2.73 16.55 535 1.31 2 Flora S 2.73 14.99 23804 Haber 532.2 0.63 2 Vestian S 2.68 15.22 520 1.00 3 NEO S 1.71 16.20 502 0.37 2 Jupiter trojan C 13.88 13.02 500.6 0.88 2 MBA C 11.33 13.46 6498 Ko 500 0.60 2 Flora S 3.99 14.16 500 0.81 2 NEO S 0.90 17.60
Periods of 400+ hours # Minor planet designation Rotation period(hours) Δmag Quality(U) Orbit or family Spectral type Diameter(km) Abs. mag(H) Refs 499.6 0.46 2 MBA S 1.01 17.33 79316 Huangshan 493 0.62 2+ Hungaria E 2.54 14.90 1220 Crocus 491.4 1.00 3 Eos S 15.79 11.76 1256 Normannia 488.1 0.39 2 Hilda D 69.02 10.02 482.3 0.46 2 Nysa S 3.12 14.84 2696 Magion 480 0.31 2 Phocaea S 10.06 12.20 5171 Augustesen 480 0.80 3 Vestian S 6.50 13.30 19204 Joshuatree 480 0.95 2+ Phocaea S 4.39 14.00 20862 Jenngoedhart 479.3 1.08 2 Flora S 3.59 14.39 2759 Idomeneus 479 0.27 3− Jupiter trojan C 60.90 10.00 473 0.38 3 NEO S 0.59 18.50 467.3 0.57 2 Jupiter trojan C 23.00 11.92 463.7 0.83 2 Flora S 0.86 17.50 6141 Durda 460 0.50 2+ Hungaria E 3.35 14.30 6183 Viscome 453 0.90 3− Mars crosser S 5.41 13.70 450 1.20 2 NEO S 0.16 21.30 449.5 0.62 2 MBA C 5.80 14.91 448 0.42 2 Hungaria E 3.06 14.50 447.6 0.40 2 MBA S 2.36 15.50 446.5 0.39 2 MBA C 7.58 14.33 11351 Leucus 445.7 0.70 3− Jupiter trojan C 42.07 10.70 2747 Český Krumlov 438.7 0.63 2 MBA C 20.62 12.16 436.7 0.32 2 MBA S 1.17 17.02 437 Rhodia 433.2 0.35 3− MBA S 14.46 10.71 319 Leona 430 0.50 3 MBA C 68.01 10.10 427.4 0.60 2 MBA C 3.85 15.80 426 1.13 2 Mars crosser S 2.59 15.30 425 0.49 2 NEO S 0.45 19.10 3571 Milanstefanik 421.1 0.65 2+ Hilda C 38.91 11.00 418.9 0.37 2 Eunomia S 5.25 13.71 5641 McCleese 418 1.30 2 Hungaria A 3.67 14.10 253 Mathilde 417.7 0.50 3 MBA C 57.87 10.30 17030 Sierks 416.2 0.31 2 MBA C 10.57 13.61 707 Steina 414 1.00 2+ Flora S 10.31 12.10 412.7 0.84 2 MBA S 3.61 15.33 9584 Louchheim 410 0.30 2 MBA S 4.50 14.10 3759 Piironen 409.8 0.56 2 Eunomia C 32.15 11.90 408.9 0.83 2 Nysa S 1.20 16.92 10684 Babkina 404.7 0.74 2 Flora S 2.43 15.24
Periods of 300+ hours # Minor planet designation Rotation period(hours) Δmag Quality(U) Orbit or family Spectral type Diameter(km) Abs. mag(H) Refs 397.2 0.58 2 Eunomia S 1.59 16.30 21432 Polingloh 393 0.73 2 Flora S 1.52 16.25 392 1.40 3 Hungaria E 2.54 14.90 22905 Liciniotoso 389.6 0.42 2 Flora S 2.50 15.18 386.9 0.62 2 Flora S 0.98 17.20 383.5 0.71 2 Eunomia S 3.01 14.92 383.3 0.80 2 MBA C 3.38 16.08 380 0.90 2 Hungaria E 2.30 14.80 10331 Peterbluhm 379 1.10 2 Hilda C 23.21 11.90 136199 Eris 378.9 0.30 3 TNO (neutral) 2326.0 -1.21 376 0.74 2 Flora S 0.94 17.31 375.4 0.86 2 Eos S 2.88 15.46 375 0.80 3− Jupiter trojan C 29.21 11.40 375 0.59 2 Jupiter trojan C 29.21 11.40 1750 Eckert 375 0.87 3− Hungaria S 6.97 13.15 374.8 0.58 2 Jupiter trojan C 18.30 12.42 5075 Goryachev 373 1.00 2 Nysa S 5.28 13.70 8026 Johnmckay 372 1.00 3 Hungaria E 2.54 14.90 368.5 0.74 2 MBA C 4.29 15.57 5851 Inagawa 367.5 0.90 3 Eunomia S 9.60 12.40 367.1 0.54 2 Flora S 3.53 14.43 367 0.23 2 Hungaria E 2.92 14.60 8485 Satoru 362.8 0.58 2 MBA C 10.11 13.70 362.3 0.77 2 MBA S 2.54 15.34 362 0.48 2 Eos S 6.19 13.79 360.4 0.68 2 Flora S 0.65 18.09 359.1 0.40 2 Eunomia S 5.63 13.56 358 0.98 2+ Jupiter trojan C 24.30 11.80 356.4 0.48 2 MBA C 9.14 13.92 4024 Ronan 356 1.10 3− Flora S 6.51 13.10 353.9 0.48 2 MBA C 2.81 16.49 10374 Etampes 353 0.23 2 Flora S 4.09 14.11 351.9 0.42 2 MBA S 3.42 15.44 630 Euphemia 350 0.45 2 Eunomia S 17.14 11.10 350 0.17 2 Hungaria E 1.93 15.50 348.7 0.70 2 Jupiter trojan C 11.67 13.39 347 0.34 2+ Nysa S 2.77 15.10 346.9 0.26 2 Jupiter trojan C 14.56 12.91 346 0.43 2 Jupiter trojan C 30.59 11.30 2487 Juhani 344.6 1.03 2 MBA S 7.13 13.10 344.1 0.75 2 Jupiter trojan C 27.20 11.56 337.8 0.18 2 MBA C 12.30 13.28 4962 Vecherka 336 1.08 2 Eunomia S 10.06 12.30 7430 Kogure 335.9 0.57 2 MBA S 7.82 12.90 335.5 0.54 2 Eunomia S 3.37 14.67 10551 Göteborg 335.3 0.70 2 Eos S 11.53 12.44 8942 Takagi 332.2 0.44 2 MBA C 6.91 14.53 331.6 0.84 2 MBA S 3.05 15.69 331 0.39 2+ Hilda C 13.98 13.00 330.4 0.55 2 Flora S 0.73 17.84 12577 Samra 329.2 0.96 2 MBA C 5.72 14.94 325.1 0.74 2 MBA S 1.50 16.48 323.4 0.49 2 Eunomia S 4.43 14.08 321.6 0.91 2 MBA C 2.31 16.91 321.5 0.69 2 Koronis S 4.63 13.84 3527 McCord 321 0.44 2 Flora S 7.82 12.70 320 0.88 2 MBA C 8.76 14.02 341 California 318 0.92 3 Flora S 14.67 10.55 16879 Campai 314.2 0.68 2 MBA C 10.61 13.60 14040 Andrejka 310 0.95 2 Flora S 2.26 15.40 309.7 0.92 2 Eunomia S 5.44 13.63 309.7 0.82 2 MBA C 7.26 14.42 309.3 0.40 2 Themis C 7.38 14.02 1807 Slovakia 308.6 1.10 3 MBA S 9.84 12.40 308.1 0.54 2 MBA S 2.22 15.63 8807 Schenk 307.6 0.44 2 MBA S 4.17 14.26 306.7 0.54 2 Eos S 6.07 13.84 306.7 0.72 2 MBA S 2.06 16.55 79360 Sila–Nunam 300.2 0.15 2 TNO C 330.77 5.52
Periods of 200+ hours