constellation
constellation
(kon-stĕ-lay -shŏn) Any of the 88 areas into which astronomers have divided the whole of the northern and southern hemispheres of the sky (or celestial sphere). Every star, galaxy, nebula, or other celestial body lies within, or sometimes overlaps, the boundaries of one of the constellations. These boundaries were established unambiguously by the International Astronomical Union in 1930 along arcs of right ascension and declination for the epoch 1875, Jan. 1.Originally the constellations had no fixed limits but were groups of stars considered by early civilizations to lie within the imagined outlines of mythological heroes, creatures, and other forms. In the Almagest , Ptolemy, in about ad 140, listed 48 constellations that were visible from the Mediterranean region. Their names were mostly derived from Greek and Roman mythology, which sought to explain their presence in the sky, but a few, such as Leo, the Lion, may be of much earlier origin. During the 16th, 17th, and 18th centuries many new groupings were identified and named (and several later discarded), especially in the previously uncharted regions of the southern hemisphere. These new groupings appeared principally in star atlases published by Bayer and Hevelius in the 17th century and Lacaille in the 18th. Since then further additions have proved unacceptable.
The constellations seen on any clear night depend on the latitude of the observer and change with the time of year and time of night. If, for a particular latitude, ⊂, the stars are circumpolar stars (never set), they will be visible on every night of the year. Circumpolar stars are those with declinations greater than 90 – ⊂°. Other stars never rise above the horizon at all: for observers in the northern hemisphere, these are the ones that have declinations beyond ⊂ – 90°; for observers in the southern hemisphere, they are the ones with declinations of ⊂ + 90° (note that southern latitudes, like southern declinations, are taken to be negative for these calculations). The remaining stars can be seen only when they are above the horizon during the night, a star rising earlier, on average, by about two hours per month.
Each constellation bears a Latin name, as with Canis Major, the genitive form of which is used with the appropriate letter or number for the star name (see stellar nomenclature), as with Alpha Canis Majoris. For simplification the three-letter abbreviations for the constellations are more usually used, as with CMa. See Table 5, backmatter.
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Constellation
(religion, spiritualism, and occult)A constellation is a collection of stars that the ancients grouped together, identified with a figure from mythology, and named after that figure. In astrology, the names of the various signs of the zodiac are taken from 12 constellations intersected by the ecliptic. The untutored eye has a difficult time discerning the relationship between these star groups and the figures they are said to represent: Unlike the ancients, who gazed upon a sky filled with legends, heroes, and heroines, we moderns look up to see only a confused mass of tiny lights.
constellation
[‚kän·stə′lā·shən]Netscape Netcaster
A component of the earlier Netscape Communicator that provided a push model delivery system based on Marimba's Castanet Tuner. Users were able to subscribe to content channels on the Internet and receive information updates in the background while working on other applications. See Netscape Communicator.Constellation
in modern astronomy, any one of the sections into which the celestial sphere is divided in order to facilitate orientation in the stellar sky. In antiquity, however, constellations were the symbolic figures formed by bright stars. The most important constellations bore names borrowed from mythology, for example, Hercules and Perseus, or from everyday life, such as Libra and Lyra. The grouping of stars into constellations has no scientific significance. The entire sky is divided into 88 constellations, which were officially designated by the International Astronomical Union in 1930. (SeeSTELLAR SKY for a list of the constellations.)