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Rotation period (astronomy)
Time that it takes to complete one revolution relative to the background stars

In astronomy, the rotation period or spin period of a celestial object (e.g., star, planet, moon, asteroid) has two definitions. The first one corresponds to the sidereal rotation period (or sidereal day), i.e., the time that the object takes to complete a full rotation around its axis relative to the background stars (inertial space). The other type of commonly used "rotation period" is the object's synodic rotation period (or solar day), which may differ, by a fraction of a rotation or more than one rotation, to accommodate the portion of the object's orbital period around a star or another body during one day.

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Measuring rotation

For solid objects, such as rocky planets and asteroids, the rotation period is a single value. For gaseous or fluid bodies, such as stars and giant planets, the period of rotation varies from the object's equator to its pole due to a phenomenon called differential rotation. Typically, the stated rotation period for a giant planet (such as Jupiter, Saturn, Uranus, Neptune) is its internal rotation period, as determined from the rotation of the planet's magnetic field. For objects that are not spherically symmetrical, the rotation period is, in general, not fixed, even in the absence of gravitational or tidal forces. This is because, although the rotation axis is fixed in space (by the conservation of angular momentum), it is not necessarily fixed in the body of the object itself. As a result of this, the moment of inertia of the object around the rotation axis can vary, and hence the rate of rotation can vary (because the product of the moment of inertia and the rate of rotation is equal to the angular momentum, which is fixed). For example, Hyperion, a moon of Saturn, exhibits this behaviour, and its rotation period is described as chaotic.

Rotation period of selected objects

Celestial objectsRotation period with respect to distant stars, the sidereal rotation period (compared to Earth's mean Solar days)Synodic rotation period (mean Solar day)Apparent rotational periodviewed from Earth
Sun225.379995 days (Carrington rotation)35 days (high latitude)25d 9h 7m 11.6s35d~28 days (equatorial)3
Mercury58.6462 days458d 15h 30m 30s176 days5
Venus−243.0226 days67−243d 0h 33m−116.75 days8
Earth0.99726968 days9100d 23h 56m 4.0910s1.00 days (24h 00m 00s)
Moon27.321661 days11 (equal to sidereal orbital period due to spin-orbit locking, a sidereal lunar month)27d 7h 43m 11.5s29.530588 days12 (equal to synodic orbital period, due to spin-orbit locking, a synodic lunar month)none (due to spin-orbit locking)
Mars1.02595675 days131d 0h 37m 22.663s1.0274912514 days
Ceres0.37809 days150d 9h 4m 27.0s0.37818 days
Jupiter0.41354 days(average)0.4135344 days (deep interior16)0.41007 days (equatorial)0.4136994 days (high latitude)0d 9h 55m 30s170d 9h 55m 29.37s180d 9h 50m 30s190d 9h 55m 43.63s200.41358 d (9 h 55 m 33 s)21 (average)
Saturn0.44002+0.00130−0.00091 days (average, deep interior22)0.44401 days (deep interior23)0.4264 days (equatorial)0.44335 days (high latitude)10h 33m 38s + 1m 52s− 1m 19s 24250d 10h 39m 22.4s260d 10h 13m 59s270d 10h 38m 25.4s280.43930 d (10 h 32 m 36 s)29
Uranus−0.71833 days3031−0d 17h 14m 24s−0.71832 d (−17 h 14 m 23 s)32
Neptune0.67125 days330d 16h 6m 36s0.67125 d (16 h 6 m 36 s)34
Pluto−6.38718 days3536 (synchronous with Charon)–6d 9h 17m 32s−6.38680 d (–6d 9h 17m 0s)37
Haumea0.1631458 ±0.0000042 days380d 3h 56m 43.80 ±0.36s0.1631461 ±0.0000042 days
Makemake0.9511083 ±0.0000042 days3922h 49m 35.76 ±0.36s0.9511164 ±0.0000042 days
Eris~15.786 days40~15d 18h 53m~15.7872 days

See also

Notes

References

  1. "Period". COSMOS - The SAO Encyclopedia of Astronomy. Retrieved 2023-08-03. https://astronomy.swin.edu.au/cosmos/p/Period ↩

  2. See Solar rotation for more detail. /wiki/Solar_rotation ↩

  3. Phillips, Kenneth J. H. (1995). Guide to the Sun. Cambridge University Press. pp. 78–79. ISBN 978-0-521-39788-9. 978-0-521-39788-9 ↩

  4. Allen, Clabon Walter & Cox, Arthur N. (2000). Allen's Astrophysical Quantities. Springer. p. 296. ISBN 0-387-98746-0. 0-387-98746-0 ↩

  5. "ESO". ESO. Retrieved 2021-06-03. https://www.eso.org/public/outreach/eduoff/vt-2004/mt-2003/mt-mercury-rotation.html ↩

  6. This rotation is negative because the pole which points north of the invariable plane rotates in the opposite direction to most other planets. /wiki/Invariable_plane ↩

  7. Margot, Jean-Luc; Campbell, Donald B.; Giorgini, Jon D.; et al. (29 April 2021). "Spin state and moment of inertia of Venus". Nature Astronomy. 5 (7): 676–683. arXiv:2103.01504. Bibcode:2021NatAs...5..676M. doi:10.1038/s41550-021-01339-7. S2CID 232092194. /wiki/ArXiv_(identifier) ↩

  8. "How long is a day on Venus?". TE AWAMUTU SPACE CENTRE. Retrieved 2021-06-03. https://www.spacecentre.nz/resources/faq/solar-system/venus/day.html ↩

  9. Allen, Clabon Walter & Cox, Arthur N. (2000). Allen's Astrophysical Quantities. Springer. p. 296. ISBN 0-387-98746-0. 0-387-98746-0 ↩

  10. Reference adds about 1 ms to Earth's stellar day given in mean solar time to account for the length of Earth's mean solar day in excess of 86400 SI seconds. /wiki/SI ↩

  11. Allen, Clabon Walter & Cox, Arthur N. (2000). Allen's Astrophysical Quantities. Springer. p. 308. ISBN 0-387-98746-0. 0-387-98746-0 ↩

  12. Allen, Clabon Walter & Cox, Arthur N. (2000). Allen's Astrophysical Quantities. Springer. p. 308. ISBN 0-387-98746-0. 0-387-98746-0 ↩

  13. Allen, Clabon Walter & Cox, Arthur N. (2000). Allen's Astrophysical Quantities. Springer. p. 296. ISBN 0-387-98746-0. 0-387-98746-0 ↩

  14. Allison, Michael; Schmunk, Robert. "Mars24 Sunclock — Time on Mars". NASA GISS. https://www.giss.nasa.gov/tools/mars24/help/notes.html ↩

  15. Chamberlain, Matthew A.; Sykes, Mark V.; Esquerdo, Gilbert A. (2007). "Ceres lightcurve analysis – Period determination". Icarus. 188 (2): 451–456. Bibcode:2007Icar..188..451C. doi:10.1016/j.icarus.2006.11.025. /wiki/Icarus_(journal) ↩

  16. Rotation period of the deep interior is that of the planet's magnetic field. ↩

  17. Allen, Clabon Walter & Cox, Arthur N. (2000). Allen's Astrophysical Quantities. Springer. p. 296. ISBN 0-387-98746-0. 0-387-98746-0 ↩

  18. Allen, Clabon Walter & Cox, Arthur N. (2000). Allen's Astrophysical Quantities. Springer. p. 296. ISBN 0-387-98746-0. 0-387-98746-0 ↩

  19. Allen, Clabon Walter & Cox, Arthur N. (2000). Allen's Astrophysical Quantities. Springer. p. 296. ISBN 0-387-98746-0. 0-387-98746-0 ↩

  20. Allen, Clabon Walter & Cox, Arthur N. (2000). Allen's Astrophysical Quantities. Springer. p. 296. ISBN 0-387-98746-0. 0-387-98746-0 ↩

  21. Seligman, Courtney. "Rotation Period and Day Length". Retrieved June 12, 2021. http://cseligman.com/text/sky/rotationvsday.htm ↩

  22. Found through examination of Saturn's C Ring /wiki/Rings_of_Saturn#C_Ring ↩

  23. Rotation period of the deep interior is that of the planet's magnetic field. ↩

  24. McCartney, Gretchen; Wendel, JoAnna (18 January 2019). "Scientists Finally Know What Time It Is on Saturn". NASA. Retrieved 18 January 2019. https://www.jpl.nasa.gov/news/news.php?feature=731 ↩

  25. Mankovich, Christopher; et al. (17 January 2019). "Cassini Ring Seismology as a Probe of Saturn's Interior. I. Rigid Rotation". The Astrophysical Journal. 871 (1): 1. arXiv:1805.10286. Bibcode:2019ApJ...871....1M. doi:10.3847/1538-4357/aaf798. S2CID 67840660. https://doi.org/10.3847%2F1538-4357%2Faaf798 ↩

  26. Kaiser, M. L.; et al. (1980). "Voyager Detection of Nonthermal Radio Emission from Saturn". Science. 209 (4462): 1238–1240. Bibcode:1980Sci...209.1238K. doi:10.1126/science.209.4462.1238. hdl:2060/19800013712. PMID 17811197. S2CID 44313317. https://www.science.org/doi/10.1126/science.209.4462.1238 ↩

  27. Abel, Paul (2013). "Saturn". Visual Lunar and Planetary Astronomy. The Patrick Moore Practical Astronomy Series. New York, NY: Springer. pp. 149–171. doi:10.1007/978-1-4614-7019-9_8. ISBN 978-1-4614-7018-2. 978-1-4614-7018-2 ↩

  28. Abel, Paul (2013). "Saturn". Visual Lunar and Planetary Astronomy. The Patrick Moore Practical Astronomy Series. New York, NY: Springer. pp. 149–171. doi:10.1007/978-1-4614-7019-9_8. ISBN 978-1-4614-7018-2. 978-1-4614-7018-2 ↩

  29. Seligman, Courtney. "Rotation Period and Day Length". Retrieved June 12, 2021. http://cseligman.com/text/sky/rotationvsday.htm ↩

  30. Allen, Clabon Walter & Cox, Arthur N. (2000). Allen's Astrophysical Quantities. Springer. p. 296. ISBN 0-387-98746-0. 0-387-98746-0 ↩

  31. This rotation is negative because the pole which points north of the invariable plane rotates in the opposite direction to most other planets. /wiki/Invariable_plane ↩

  32. Seligman, Courtney. "Rotation Period and Day Length". Retrieved June 12, 2021. http://cseligman.com/text/sky/rotationvsday.htm ↩

  33. Allen, Clabon Walter & Cox, Arthur N. (2000). Allen's Astrophysical Quantities. Springer. p. 296. ISBN 0-387-98746-0. 0-387-98746-0 ↩

  34. Seligman, Courtney. "Rotation Period and Day Length". Retrieved June 12, 2021. http://cseligman.com/text/sky/rotationvsday.htm ↩

  35. Allen, Clabon Walter & Cox, Arthur N. (2000). Allen's Astrophysical Quantities. Springer. p. 296. ISBN 0-387-98746-0. 0-387-98746-0 ↩

  36. This rotation is negative because the pole which points north of the invariable plane rotates in the opposite direction to most other planets. /wiki/Invariable_plane ↩

  37. Seligman, Courtney. "Rotation Period and Day Length". Retrieved June 12, 2021. http://cseligman.com/text/sky/rotationvsday.htm ↩

  38. Lacerda, Pedro; Jewitt, David & Peixinho, Nuno (2008-04-02). "High-Precision Photometry of Extreme KBO 2003 EL61". The Astronomical Journal. 135 (5): 1,749–1,756. arXiv:0801.4124. Bibcode:2008AJ....135.1749L. doi:10.1088/0004-6256/135/5/1749. S2CID 115712870. Retrieved 2008-09-22. http://www.iop.org/EJ/abstract/1538-3881/135/5/1749 ↩

  39. T. A. Hromakina; I. N. Belskaya; Yu. N. Krugly; V. G. Shevchenko; J. L. Ortiz; P. Santos-Sanz; R. Duffard; N. Morales; A. Thirouin; R. Ya. Inasaridze; V. R. Ayvazian; V. T. Zhuzhunadze; D. Perna; V. V. Rumyantsev; I. V. Reva; A. V. Serebryanskiy; A. V. Sergeyev; I. E. Molotov; V. A. Voropaev; S. F. Velichko (2019-04-09). "Long-term photometric monitoring of the dwarf planet (136472) Makemake". Astronomy & Astrophysics. 625: A46. arXiv:1904.03679. Bibcode:2019A&A...625A..46H. doi:10.1051/0004-6361/201935274. S2CID 102350991. /wiki/ArXiv_(identifier) ↩

  40. Szakáts, R.; Kiss, Cs.; Ortiz, J. L.; Morales, N.; Pál, A.; Müller, T. G.; et al. (2023). "Tidally locked rotation of the dwarf planet (136199) Eris discovered from long-term ground based and space photometry". Astronomy & Astrophysics. L3: 669. arXiv:2211.07987. Bibcode:2023A&A...669L...3S. doi:10.1051/0004-6361/202245234. S2CID 253522934. /wiki/ArXiv_(identifier) ↩