occultation(redirected from Occultation (astronomy))
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occultation(ŏk'əltā`shən), in astronomy, eclipse of one celestial body by another, e.g., when the moon lies between a star and the earth. Occultations of stars by the moon are important in astronomy. Since stellar positions are very accurately known, the time and position of an occultation can be used to determine the position of the moon. Alternatively, an observer can determine his or her longitudelongitude
, angular distance on the earth's surface measured along any latitude line such as the equator east or west of the prime meridian. A meridian of longitude is an imaginary line on the earth's surface from pole to pole; two opposite meridians form a great circle dividing
..... Click the link for more information. by comparing the time at which he observes an occultation with a table listing the universal timeuniversal time
(UT), the international time standard common to every place in the world, it nominally reflects the mean solar time along the earth's prime meridian (renumbered to equate to civil time).
..... Click the link for more information. at which the occultation occurs.
occultation(ok-ul-tay -shŏn) Complete or partial obscuration of an astronomical object by another of larger apparent diameter, especially the Moon or a planet. A solar eclipse is strictly an occultation. The precise timings of occultations provide information about planetary atmospheres, the dimensions of extended visible, radio, and X-ray objects, and the positions of objects, such as distant radio sources. See also eclipse; grazing occultation.
Occultation(religion, spiritualism, and occult)
An occultation (from the Latin occultus, meaning “to hide”) is an eclipse of a star or planet by another heavenly body, particularly by the Moon. Despite its seemingly “exotic” connotation, it is a commonly used term in astronomy as well as in astrology. The astrological importance, if any, of occultations has been hotly debated. Part of what is at issue in this debate is competing theories of celestial influence. If, as one school of thought asserts, astrology works via the mechanism of acausal synchronicity, then occultations should have no influence beyond what one would expect from a simple conjunction. If, however, the celestial bodies influence events on Earth through forces analogous to gravity or electromagnetism, then an occultation should have a measurable effect on the star or planet that has been “occulted,” especially when it is being eclipsed by a large body like the Sun. Certain experiments, such as those in which the Kolisko effect has been observed, seem to corroborate the latter view.
in astronomy, a phenomenon in which to an observer on earth one celestial body is hidden by another. Occultations of stars and planets by the moon as it travels around the earth are encountered most frequently. The occultation of the sun by the moon is called a solar eclipse. The term “occultation” is also sometimes used to refer to a transit, in which a heavenly body passes across the larger, and more distant, visible disk of another heavenly body, for example, the transits of inferior planets across the sun’s disk and the transits of planetary satellites across the disks of the planets themselves. With the development of spaceflight and new methods of observation, the concept of occultation has been expanded to include occultations of radio emission sources in space and of celestial bodies by the earth, as observed from space.
In the occultation of stars by the moon—the most frequently observed occultation—the moments at which a star appears and disappears at the lunar limb are detected to within ±0.01 sec by means of photoelectric instruments. Results from many years of observation of the occultation of stars by the moon at various observatories are used to refine the theory of the moon’s rotation about the earth and to study fluctuations in the earth’s rate of rotation about its axis. The latter study is necessary in order to make ephemeris time corrections in studying irregularities of the lunar limb. Observations of the transit of planets across the sun’s disk have made it possible to detect and study the atmospheres of the planets. Radio-astronomical methods of studying occultations of radio emission sources in outer space by bodies of the solar system make possible descriptions of the structure of radio sources.
REFERENCEMikhailov, A. A. Teoriia zatmenii, 2nd ed. Moscow, 1954.
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