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sidereal time
sidereal time Time as measured by reference to the stars; technically, it is the hour angle of the vernal equinox. The sidereal time is the same as the right ascension of stars currently on the observer's meridian. More generally, the sidereal time is the sum of the right ascension and the hour angle of any celestial object, and hence links these two coordinates. Depending on whether the true equinox or the mean equinox is used as the reference point, the resulting form of sidereal time is known as either apparent sidereal time or mean sidereal time, respectively. Their difference, which seldom exceeds a second of time, is called the equation of the equinoxes. See also greenwich sidereal time; local sidereal time.
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"sidereal time." A Dictionary of Astronomy. 1997. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "sidereal time." A Dictionary of Astronomy. 1997. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O80-siderealtime.html "sidereal time." A Dictionary of Astronomy. 1997. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O80-siderealtime.html |
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sidereal time
sidereal time (ST), time measured relative to the fixed stars; thus, the sidereal day is the period during which the earth completes one rotation on its axis so that some chosen star appears twice on the observer's celestial meridian . Because the earth moves in its orbit about the sun, the sidereal day is about 4 min shorter than the solar day (see solar time ). Thus, a given star will appear to rise 4 min earlier each night, so that different stars are visible at different times of the year. The local sidereal time of an observer is equal to the hour angle of the vernal equinox. |
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"sidereal time." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "sidereal time." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1E1-sidrltim.html "sidereal time." The Columbia Encyclopedia, 6th ed.. 2011. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-sidrltim.html |
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sidereal period
sidereal period Orbital period of a planet or other celestial body with respect to a background star. It is the true orbital period. Sidereal time is local time reckoned according to the rotation of the Earth with respect to the stars. The sidereal day is 23 hours, 56 minutes and 4 seconds of mean solar time, nearly 4 minutes shorter than the mean solar day. The sidereal year is equal to 365.25636 mean solar days.
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"sidereal period." World Encyclopedia. 2005. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "sidereal period." World Encyclopedia. 2005. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O142-siderealperiod.html "sidereal period." World Encyclopedia. 2005. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O142-siderealperiod.html |
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sidereal period
sidereal period The time taken for a planet or satellite to complete one orbit relative to the stars. For example, the Earth's sidereal period is a sidereal year, and the Moon's sidereal period is a sidereal month. However, a body's axial spin can also be measured relative to the stars, and this is termed the sidereal period of axial rotation; the Earth's sidereal period of axial rotation is the sidereal day.
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Cite this article
"sidereal period." A Dictionary of Astronomy. 1997. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "sidereal period." A Dictionary of Astronomy. 1997. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O80-siderealperiod.html "sidereal period." A Dictionary of Astronomy. 1997. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O80-siderealperiod.html |
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sidereal day
sidereal day The time it takes for the Earth to complete one rotation on its axis such that a particular point on the surface returns to its former position in relation to the position of the fixed stars. The sidereal day is 4.09 minutes shorter than the mean solar day, because the movement of the Earth in its solar orbit is imposed on its rotational motion.
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AILSA ALLABY and MICHAEL ALLABY. "sidereal day." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. AILSA ALLABY and MICHAEL ALLABY. "sidereal day." A Dictionary of Earth Sciences. 1999. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O13-siderealday.html AILSA ALLABY and MICHAEL ALLABY. "sidereal day." A Dictionary of Earth Sciences. 1999. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O13-siderealday.html |
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sidereal year
sidereal year 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 ). It is 20 min longer than the tropical year because of the precession of the equinoxes ; for this reason, the sidereal year does not stay in step with the seasons. |
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Cite this article
"sidereal year." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "sidereal year." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1E1-sidrlyr.html "sidereal year." The Columbia Encyclopedia, 6th ed.. 2011. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-sidrlyr.html |
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sidereal day
sidereal day The interval of time between successive transits of the mean equinox, equal to 23 h 56 m 04 s. Because of the precession of the equinoxes, the mean equinox is not a completely fixed sidereal point. As a result the sidereal day is 0.0084 s shorter than the Earth's rotation period relative to the stars.
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Cite this article
"sidereal day." A Dictionary of Astronomy. 1997. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "sidereal day." A Dictionary of Astronomy. 1997. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O80-siderealday.html "sidereal day." A Dictionary of Astronomy. 1997. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O80-siderealday.html |
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sidereal day
si·de·re·al day • n. Astron. the time between two consecutive transits of the First Point of Aries. It represents the time taken by the earth to rotate on its axis relative to the stars, and is almost four minutes shorter than the solar day because of the earth's orbital motion. |
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"sidereal day." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "sidereal day." The Oxford Pocket Dictionary of Current English. 2009. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O999-siderealday.html "sidereal day." The Oxford Pocket Dictionary of Current English. 2009. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O999-siderealday.html |
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year
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"year." World Encyclopedia. 2005. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "year." World Encyclopedia. 2005. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O142-year.html "year." World Encyclopedia. 2005. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O142-year.html |
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sidereal year
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Cite this article
"sidereal year." A Dictionary of Astronomy. 1997. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "sidereal year." A Dictionary of Astronomy. 1997. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1O80-siderealyear.html "sidereal year." A Dictionary of Astronomy. 1997. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1O80-siderealyear.html |
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sidereal period
sidereal period in astronomy, length of time a body takes to complete an orbit relative to the fixed stars. See sidereal time . |
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Cite this article
"sidereal period." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "sidereal period." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1E1-sidrlprd.html "sidereal period." The Columbia Encyclopedia, 6th ed.. 2011. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-sidrlprd.html |
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sidereal day
sidereal day see sidereal time . |
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Cite this article
"sidereal day." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. 27 May. 2012 <http://www.encyclopedia.com>. "sidereal day." The Columbia Encyclopedia, 6th ed.. 2011. Encyclopedia.com. (May 27, 2012). http://www.encyclopedia.com/doc/1E1-X-sidrlday.html "sidereal day." The Columbia Encyclopedia, 6th ed.. 2011. Retrieved May 27, 2012 from Encyclopedia.com: http://www.encyclopedia.com/doc/1E1-X-sidrlday.html |
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