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nounthe branch of physics that studies celestial bodies and the universe as a whole
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Definition that contains astronomy
- ha (astronomy) the angular distance of a celestial point measured westward along the celestial equator from the zenith crossing; the right ascension for an observer at a particular location and time of day
- star (astronomy) a celestial body of hot gases that radiates energy derived from thermonuclear reactions in the interior
- planet (astronomy) any of the nine large celestial bodies in the solar system that revolve around the sun and shine by reflected light; Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto in order of their proximity to the sun; viewed from the constellation Hercules, all the planets rotate around the sun in a counterclockwise direction
- maya a member of an American Indian people of Yucatan and Belize and Guatemala who had a culture (which reached its peak between AD 300 and 900) characterized by outstanding architecture and pottery and astronomy
- coma (astronomy) the luminous cloud of particles surrounding the frozen nucleus of a comet; forms as the comet approaches the sun and is warmed
- phase (astronomy) the particular appearance of a body's state of illumination (especially one of the recurring shapes of the part of Earth's moon that is illuminated by the sun)
- primary (astronomy) a celestial body (especially a star) relative to other objects in orbit around it
- galaxy (astronomy) a collection of star systems; any of the billions of systems each having many stars and nebulae and dust
- ra (astronomy) the equatorial coordinate specifying the angle, measured eastward along the celestial equator, from the vernal equinox to the intersection of the hour circle that passes through an object in the sky; usually expressed in hours and minutes and seconds; used with declination to specify positions on the celestial sphere
- canal (astronomy) an indistinct surface feature of Mars once thought to be a system of channels; they are now believed to be an optical illusion