Periodic comets (also known as short-period comets) are comets with orbital periods of less than 200 years or that have been observed during more than a single perihelion passage (e.g. 153P/Ikeya–Zhang). "Periodic comet" is also sometimes used to mean any comet with a periodic orbit, even if greater than 200 years.
Periodic comets receive a permanent number prefix usually after the second perihelion passage, which is why there are a number of unnumbered periodic comets, such as . Comets that are not observed after a number of perihelion passages, or presumed to be destroyed, are given the D designation, and likewise comets given a periodic number and subsequently lost are given [n]D instead of [n]P, such as 3D/Biela or 5D/Brorsen.
In nearly all cases, comets are named after their discoverers, but in a few cases such as 2P/Encke and 27P/Crommelin they were named for a person who determined their orbits. The long-term orbits of comets can be difficult to calculate due to errors in the known trajectory that can accumulate from perturbations from the planets. Even so, quite a few comets were lost because their orbits are also affected by non-gravitational effects such as the release of gas and other material that forms the comet's coma and tail. Unlike a long-period comet, the next perihelion passage of a numbered periodic comet can be predicted with a high degree of accuracy.
Periodic comets sometimes bear the same name repeatedly (e.g. the nine Shoemaker–Levy comets or the twenty-four NEAT comets); the IAU system distinguishes between them either through the number prefix or by the full designation (e. g. 181P and 192P/Shoemaker–Levy are both "Comet Shoemaker–Levy"). In the literature, an informal numbering system is applied to periodic comets (skipping the non-periodic ones), thus 181P and 192P are known as Comet Shoemaker–Levy 6 and Comet Shoemaker–Levy 1, respectively. Non-periodic Shoemaker–Levy comets are interleaved in this sequence: C/1991 B1 between 2 and 3, C/1991 T2 between 5 and 6, C/1993 K1 and C/1994 E2 after Shoemaker–Levy 9.
In comet nomenclature, the letter before the "/" is either "C" (a non-periodic comet), "P" (a periodic comet), "D" (a comet that has been lost or has disintegrated), "X" (a comet for which no reliable orbit could be calculated —usually historical comets), "I" for an interstellar object, or "A" for an object that was either mistakenly identified as a comet, but is actually a minor planet, or for an object on a hyperbolic orbit that does not show cometary activity. Some lists retain the "C" prefix for comets of periods larger than about 30 years until their return is confirmed.Comet names and designations
List of Halley-type comets
List of unnumbered Encke-type comets Comet designation Name/discoverer(s) Period(years) e a(AU) q(AU) i(°) Abs.mag.(M1) Nucleus radii Last observedperihelion Nextperihelion Ref D/1977 C1 Skiff–Kosai 7.54 0.2592 3.847 2.850 3.20 8.5 1976/08/03 unknown P/2005 L1 McNaught 5 7.92 0.20924 3.9745 3.1428 7.7369 10.2 2005/12/13 2013/11/14 P/2013 R3 Catalina–PanSTARRS 1 5.28 0.27345 3.03293 2.20358 0.89893 6.4 0.4 km 2013/08/05 2018/11/15 P/2013 R3-A Catalina–PanSTARRS 1 5.28 0.2733 3.0327 2.2038 0.898 0.2 km 2013/08/05 2018/11/15 P/2013 R3-B Catalina–PanSTARRS 1 5.28 0.2733 3.0327 2.2038 0.8996 2013/08/05 2018/11/15 P/2015 X6 PanSTARRS 52 4.57 0.1700 2.756 2.2873 4.5583 16.1 0.3 km 2016/03/18 2020/07/08 P/2016 G1 PanSTARRS 55 4.15 0.21003 2.58322 2.04068 10.9685 14.7 2017/01/26 2021/03/21 PanSTARRS 5.01 0.0320 2.929 2.835 15.70 14.7 2015/07/03 P/2017 S8 PanSTARRS 70 4.63 0.393696 2.77621 1.68322 29.85994 14.8 2018/01/28 2022/09/13 P/2019 A3 PanSTARRS 88 5.58 0.2648 3.1471 2.3134 15.366 14.9 0.4 km 2018/08/01 2024 P/2019 A4 PanSTARRS 89 4.23 0.0896 2.6135 2.3794 13.3190 15.4 0.35–0.5 km 2018/12/05 2023 P/2020 P4-B SOHO 0.9092 1.020 0.0926 28.1473 16.2 2020/08/08 P/2020 P4-C SOHO 0.9394 1.391 0.0842 37.5593 15.6 2020/08/06 P/2021 A5 PanSTARRS 117 5.32 0.1398 3.047 2.6209 18.188 15.0 1.2 km 2020/11/11 2026 P/2021 R8 Sheppard 5.24 0.2940 3.019 2.131 2.203 18.6 2021/10/07 2027 P/2022 R5 PANSTARRS 134 5.38 0.196 3.071 2.470 15.292 15.8 2022/05/27 2027 Lemmon 18 4.43 0.147 2.695 2.299 3.703 15.44 0.5 km 2024/12/30 2029 P/2024 R2 PanSTARRS 167 5.55 0.266 3.137 2.302 15.109 15.6 2024/10/01 2030 P/2024 R3 PanSTARRS 168 5.72 0.266 3.197 2.345 14.732 17.3 2024/05/07 2031 P/2025 W3 Kresken 4.06 0.12753 2.544 2.219 10.707 16.9 2025/01/09 2029 P/2025 W4 PanSTARRS 4.14 0.21111 2.579 2.034 1.298 17.3 2025/10/04 2029 P/2026 C2 PanSTARRS 6.69 0.31426 3.552 2.436 7.40 14.7 2026/07/21 2032 P/2026 N2 5.39 0.21228 3.072 2.420 2.249 17.1 2026/09/26 2032
List of unnumbered Jupiter-family comets While Jupiter-family comets are officially defined by 2 < TJupiter < 3, they can also be loosely defined as any comet with a period of less than 20 years, a relatively low inclination, and an orbit coinciding loosely with that of Jupiter. These comets are often patchily observed, as orbital interactions with the planet often cause comets' orbits to become perturbed, causing them to not be found at the expected position in the sky and subsequently lost. Additionally, their low cometary albedos and frequent proximity to the Sun compared to Oort Cloud comets cause them to much more quickly become depleted of volatiles, making them comparatively dimmer than comets with longer orbital periods.
Before 2000 Comet designation Name/discoverer(s) Period(years) e a(AU) q(AU) i(°) Abs.mag.(M1) Nucleus radii Last observedperihelion Nextperihelion Ref D/1766 G1 Helfenzrieder 4.35 0.84763 2.665 0.406 7.865 3.0–8.7 km 1766/04/26 unknown D/1895 Q1 Swift 7.2 0.65210 3.729 1.298 2.992 1895/08/21 unknown D/1978 R1 Haneda–Campos 5.97 0.66 3.29 1.10 5.95 12.9 0.5 km 1978/10/09 1985, 1991 X/1979 O3 5.44 0.33 3.09 2.07 1.75 15.8 1979/07/26 1985 P/1996 R2 Lagerkvist 7.36 0.30998 3.782 2.60964 2.6054 6.3 2024/03/10 2031/10/06 Spacewatch 4.54 0.71386 2.743 0.785 2.426 20.9 0.192 km 2025/07/21 2030 LINEAR 2 9.56 0.24393 4.5041 3.4054 5.031 11.3 5.4 km 2017/04/25 2024/11/06 P/1999 J6 SOHO 5 5.46 0.98418 3.1005 0.04906 26.61 0.024 km 2010/04/19 2026/06/18 LONEOS 6.62 0.65079 3.5272 1.23176 8.191 19.4 2024/06/09 2030/12/21 Catalina 2 8.55 0.21391 4.1806 3.2863 5.0283 9.9 9.1 km 2000/05/01 2008/11/17
2000s Comet designation Name/discoverer(s) Period(years) e a(AU) q(AU) i(°) Abs.mag.(M1) Nucleus radii Last observedperihelion Nextperihelion Ref P/2000 R2 LINEAR 15 6.1 0.5837 3.338 1.38997 3.2163 17.6 2000/09/12 2006/10/18 P/2001 H5 NEAT 2 14.68 0.6002 5.995 2.3966 8.3993 6.8 1.1 km 2001/01/28 2015/10/03 LINEAR 24 16.53 0.59391 6.49 2.6355 4.9697 15.8 2.12 km 2001/12/19 2018/06/30 C/2002 R5 SOHO 5.77 0.98526 3.21612 0.0474 14.12 2002/09/05 2008/02/02 P/2002 S7 SOHO 4 5.79 0.98496 3.22344 0.04849 13.6 2002/09/21 2008/07/06 P/2003 F2 NEAT 14 16.58 0.54219 6.503 2.9772 11.605 13.7 2003/04/14 2019/11/12 SOHO 7 4.12 0.775433 2.570078 0.57716 11.4579 19.7 0.26 km 2016/03/09 2020/05/06 LINEAR 48 11.02 0.1709 4.9523 4.1061 2.1279 12.5 10 km 2004/08/06 2015/08/13 P/2004 R3 LINEAR–NEAT 7.52 0.44184 3.8367 2.14148 7.9723 13.5 2004/05/24 2011/11/30 P/2005 E1 Tubbiolo 19.42 0.3847 7.225 4.4456 5.154 10.7 2005/03/18 2024/08/15 P/2007 K2 Gibbs 4 19.23 0.684 7.18 2.2686 7.6197 14 2007/06/08 2026/09/01 P/2007 Q2 Gilmore 13.23 0.67123 5.594 1.83902 10.2384 16.7 2007/08/23 2020/11/15 P/2007 S1 Zhao 7.4 0.34339 3.7989 2.4944 5.973 13.5 2007/12/06 2015/05/01 P/2007 T2 Kowalski 3 5.43 0.77483 3.0904 0.695863 9.89528 18.6 2007/09/19 2013/02/23 SOHO 5.4 0.9787 3.07822 0.0654 23.35 2008/12/22 2014/05/17 P/2009 B1 Boattini 4 17.3 0.63719 6.688 2.42659 22.2285 13.2 2009/02/06 2026/05/27 Catalina 10 5.41 0.740297 3.0803 0.799956 9.5926 20.6 0.215 km 2010/01/31 2015/06/30 P/2009 Y2 Kowalski 4 16.6 0.64052 6.507 2.33919 29.9296 6.1 2010/03/30 2026/11/04
2010s