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Many star names are, in origin, descriptive of the part in the constellation they are found in; thus Phecda, a corruption of Arabic فخذ الدب ( fakhdh ad-dubb, 'thigh of the bear'). Only a handful of the brightest stars have individual proper names not depending on their asterism; so Sirius ('the scorcher'), Antares ('rival of Ares ', i.e ...
Apparent retrograde motion is the apparent motion of a planet in a direction opposite to that of other bodies within its system, as observed from a particular vantage point. Direct motion or prograde motion is motion in the same direction as other bodies. While the terms direct and prograde are equivalent in this context, the former is the ...
In astronomy, the Great Rift (sometimes called the Dark Rift or less commonly the Dark River) is a dark band caused by interstellar clouds of cosmic dust that significantly obscure ( extinguish) the center and most radial sectors of the Milky Way galaxy from Earth 's perspective. In dark, clear night skies, the rift appears as clear as the ...
The use of astronomical symbols for the Sun and Moon dates to antiquity. The forms of the symbols that appear in the original papyrus texts of Greek horoscopes are a circle with one ray () for the Sun and a crescent for the Moon. [3] The modern Sun symbol, a circle with a dot (☉), first appeared in Europe in the Renaissance.
Celestial spheres. The celestial spheres, or celestial orbs, were the fundamental entities of the cosmological models developed by Plato, Eudoxus, Aristotle, Ptolemy, Copernicus, and others. In these celestial models, the apparent motions of the fixed stars and planets are accounted for by treating them as embedded in rotating spheres made of ...
Astronomical spectroscopy is the study of astronomy using the techniques of spectroscopy to measure the spectrum of electromagnetic radiation, including visible light, ultraviolet, X-ray, infrared and radio waves that radiate from stars and other celestial objects. A stellar spectrum can reveal many properties of stars, such as their chemical ...
In astronomy, a syzygy ( / ˈsɪzədʒi / SIZ-ə-jee; from Ancient Greek συζυγία (suzugía) 'union, yoke') [1] is a roughly straight-line configuration of three or more celestial bodies in a gravitational system. [2] The word is often used in reference to the Sun, Earth, and either the Moon or a planet, where the latter is in conjunction ...
Astronomical naming conventions. In ancient times, only the Sun and Moon, a few stars, and the most easily visible planets had names. Over the last few hundred years, the number of identified astronomical objects has risen from hundreds to over a billion, and more are discovered every year. Astronomers need to be able to assign systematic ...