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astronomy
source: By Gerhard Emmoser - This file was donated to Wikimedia Commons as part of a project by the Metropolitan Museum of Art. See the Image and Data Resources Open Access Policy, CC0

noun
the branch of science which deals with celestial objects, space, and the physical universe as a whole.
天文学
>In ancient times, observation of the sun, moon, stars, and planets formed the basis of timekeeping and navigation. Astronomy was greatly furthered by the invention of the optical telescope, but modern observations are made in all parts of the spectrum, including X-ray and radio frequencies, using terrestrial and orbiting instruments and space probes.

ORIGIN
Middle English (also denoting astrology): from Old French astronomie, from Latin astronomia, from Greek, from astronomos (adjective) ‘star-arranging’.