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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.
It differs from the sidereal period because the object's semi-major axis typically advances slowly. Also, the tropical period of Earth (a tropical year) is the interval between two alignments of its rotational axis with the Sun, also viewed as two passages of the object at a right ascension of 0 hr.
Apsidal precession is considered positive when the orbit's axis rotates in the same direction as the orbital motion. An apsidal period is the time interval required for an orbit to precess through 360°, [2] which takes the Earth about 112,000 years and the Moon about 8.85 years. [3]
The calculated ratio between major and minor axis of the ellipse is (4) m 1 /m 2 = ν C. where ν C is the Chandler resonance frequency. The result is in good agreement with the observations. [2] [22] From Figure 2 together with eq.(4), one obtains ν C = 0.83, corresponding to a Chandler resonance period of (5) τ C = 441 sidereal days = 1.20 ...
time interval [3] as an object – part of the time axis limited by two instants. Being an object, it has no value; duration [4] as a quantity characterizing a time interval. [5] As a quantity, it has a value, such as a number of minutes, or may be described in terms of the quantities (such as times and dates) of its beginning and end.
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 ...
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.
In 1749 Richard Dunthorne confirmed Halley's suspicion after re-examining ancient records, and produced the first quantitative estimate for the size of this apparent effect: [3] a centurial rate of +10″ (arcseconds) in lunar longitude, which is a surprisingly accurate result for its time, not differing greatly from values assessed later, e.g ...