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Sidereal time ("sidereal" pronounced / s aɪ ˈ d ɪər i əl, s ə-/ sy-DEER-ee-əl, sə-) is a system of timekeeping used especially by astronomers. Using sidereal time and the celestial coordinate system, it is easy to locate the positions of celestial objects in the night sky.
The Earth's rotational rate around its own axis is 15 minutes of arc per minute of time (360 degrees / 24 hours in day); the Earth's rotational rate around the Sun (not entirely constant) is roughly 24 minutes of time per minute of arc (from 24 hours in day), which tracks the annual progression of the Zodiac.
The anomalistic period is the time that elapses between two passages of an object at its periapsis (in the case of the planets in the Solar System, called the perihelion), the point of its closest approach to the attracting body. It differs from the sidereal period because the object's semi-major axis typically advances slowly.
However, these variations cancel out over a year. There are also other perturbations such as Earth's wobble, but these are less than a second per year. Sidereal time is time by the stars. A sidereal rotation is the time it takes the Earth to make one revolution with rotation to the stars, approximately 23 hours 56 minutes 4 seconds.
The daily arc path of an object on the celestial sphere, including the possible part below the horizon, has a length proportional to the cosine of the declination.Thus, the speed of the diurnal motion of a celestial object equals this cosine times 15° per hour, 15 arcminutes per minute, or 15 arcseconds per second.
(1) τ E = 1/ν E = A/(C − A) sidereal days ≈ 307 sidereal days ≈ 0.84 sidereal years ν E = 1.19 is the normalized Euler frequency (in units of reciprocal years), C = 8.04 × 10 37 kg m 2 is the polar moment of inertia of the Earth, A is its mean equatorial moment of inertia, and C − A = 2.61 × 10 35 kg m 2 .
Sidereal astrology is not necessarily a lesser-known form of astrology, but the reason this might be your first time hearing about it is simply because it is lesser known in the West.
27.321661 days [7] (equal to sidereal orbital period due to spin-orbit locking, a sidereal lunar month) 27 d 7 h 43 m 11.5 s: 29.530588 days [7] (equal to synodic orbital period, due to spin-orbit locking, a synodic lunar month) none (due to spin-orbit locking) Mars: 1.02595675 days [3] 1 d 0 h 37 m 22.663 s: 1.02749125 [8] days: Ceres: 0.37809 ...