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The proper motion of a star or other celestial object relative to a set of reference points.
Late 18th century; earliest use found in William Herschel (1738–1822), musician and astronomer.
雅致网英汉双解词典包含236457条英汉翻译词条，涵盖了常用英语单词及词组短语的翻译及用法，是英语学习的必备工具。