Rotation period

In astronomy, a rotation period is the time an astronomical object takes to complete one revolution around its rotation axis relative to the background stars. For the Earth this is a sidereal day. It is different from a solar day, which is measured by the passage of the Sun across the local meridian.

All celestial objects spin.^[1][2][3] The rotation period differs according to whether the body in question is solid or fluid (gaseous). A solid object has one value, but a fluid object such as a star spins differently at the poles compared to the equator (Sun: about 25 days at the equator and about 35 days near the poles).^[4][5]

1. ↑ Why and how do planets rotate?. Scientific American. 14 April 2003.
2. ↑ Ethan Siegel 2019. This is why black holes must spin at almost the speed of light. Forbes.
3. ↑ Robert Walty 2019. It is said that most black holes likely have spin. What exactly is it that spins?. astronomy.com.
4. ↑ Zell, Holly 2015. Solar rotation varies by latitude. NASA.[1]
5. ↑ Beck J. 2000. A comparison of differential rotation measurements. Solar Physics. 191: 47–70. Bibcode:2000SoPh..191...47B.doi:10.1023/A:1005226402796