Sidereal Year
Related Category: Astronomy: General
time required for the earth to complete an orbit of the sun relative to the stars. The sidereal year is 365 days, 6 hr, 9 min, 9.5 sec of mean solar time (see solar time).
sidereal year
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Sidereal Year
A sidereal year is approximately 365.256363 days (in 1994-2000), slightly longer than the solar (365.2425 days).
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In fact, sidereal years are very slightly longer than tropical years. The difference is caused by the precession of the equinoxes. One sidereal year is roughly equal to 1 + 1/26000 or 1.000039 tropical years.
See also
* Anomalistic year ...
sidereal year
the amount of time it takes one body to revolve about another with respect to the stars
siderostat ...
sidereal year The time required for the constellations to complete once cycle around the sky and return to their starting points, as seen from a given point on Earth.
SIDEREAL YEAR
A sidereal year is measured relative to the stars (the period between successive conjunctions with any star). One sidereal year, equal to 365 days, 6 hours, 9 minutes, and 9.
Sidereal year
The sidereal year is a misnomer for solar orbit. It is the time taken for the Sun to return to the same position with respect to the stars of the celestial sphere....
and tropical year
Tropical year ...
The sidereal year is the length of time that the Sun takes to return to the same position with respect to the stars of the celestial sphere.
Currently, the sidereal year -- the time it takes the Sun to return to the ecliptic longitude of a given fixed star-is about 365.2564 solar days. The sidereal year appears to be increasing slightly, about 0.01 second per century.
sidereal year the time required for the Earth to complete an exactly 360° orbit around the Sun as measured with respect to the stars = 365.2564 mean solar days (contrast with tropical year).
As on Earth, the sidereal year is not the quantity that is needed for calendar purposes. Rather, the tropical year would be likely to be used because it gives the best match to the progression of the seasons.
The sidereal year is based upon the stars. sidereal day The duration of one rotation of the earth on its axis, with respect to the vernal equinox. It is measured by successive transits of the vernal equinox over the upper branch of a meridian.
It is not clear if this would be a value for the sidereal year (actual value at his time (modern estimate) ca. 365.2565 days), but the difference with Hipparchus' value for the tropical year is consistent with his rate of precession (see below).
Our calendar year, however, is not based on the sidereal year. Most people prefer to have seasonal events happen on the same date as much as is possible. As an example, people prefer to have the March 21 as the first day of spring.
From the Earth's viewpoint therefore, the Sun reaches one point at a quarter, the other at three quarters of the way through the sidereal year: the vernal (spring) equinox is thus on or around 21 March, the autumnal on or around 22 September.
The discovery of precession enabled Hipparchus to obtain more nearly correct values for the tropical year (the period of the Sun's apparent revolution from an equinox to the same equinox again), and also for the sidereal year (the period of the Sun's ...
Owing to the precession of the equinoxes it is longer than a tropical or sidereal year by 25 minutes and 2.3 seconds. An Anomalistic month is the time in which the moon passes from perigee to perigee, &c.
Year, anomalistic. The period for successive perihelion passages of the Earth, a little less than 5 minutes longer than the sidereal year.
55 seconds in 1955, is called a sidereal year. The period of revolution from perihelion to perihelion, averaging 365 days 6 hours 13 minutes 53.16 seconds in 1955, is an anomalistic year.
-- Sidereal year, the time in which the sun, departing from any fixed star, returns to the same. This is 365 days, 6 hours, 9 minutes, and 9.3 seconds. -- Tropical year. See under Tropical. -- Year and a day O. Eng.
 See also: Year, Earth, Sun, Time, Orbit
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