as·​tron·​o·​my | \ ə-ˈsträ-nə-mē How to pronounce astronomy (audio) \
plural astronomies

Definition of astronomy

: the study of objects and matter outside the earth's atmosphere and of their physical and chemical properties

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The Difference Between Astronomy and Astrology

Some may find it easy to confuse astronomy and astrology. At one time, these two words actually were synonymous (that is, astronomy once meant what astrology means today), but they have since moved apart from each other. In current use, astronomy is concerned with “the study of objects and matter outside the earth's atmosphere,” while astrology is the purported divination of how stars and planets influence our lives. Put bluntly, astronomy is a science, and astrology is not.

Examples of astronomy in a Sentence

Recent Examples on the Web In addition to their contributions in architecture, astronomy, and writing, the Maya created sophisticated systems for healing. Jennifer Fernandez, Town & Country, "The 10 Luxury Wellness Escapes You’ll Want to Book for 2020," 5 Nov. 2019 The band’s frontman Dustin Bates is an expert on these subjects, having worked as an engineer with an interest in astronomy. John Adamian,, "Starset bringing its sci-fi self to The Webster," 18 Oct. 2019 Michael Brown, an associate professor at Monash University’s school of physics and astronomy told the New York Post of Asteroid 2019 OK. Fox News, "Asteroid size of Empire State Building set to fly by Earth next week," 2 Aug. 2019 The fact that the moon has an ionosphere is not particularly surprising, says Jasper Halekas, an associate professor of physics and astronomy at the University of Iowa. Daniel Oberhaus, WIRED, "Lunar Mysteries That Science Still Needs to Solve," 16 July 2019 The California Planet Search, which is led by California Institute of Technology professor of astronomy Andrew Howard, watched the star for years to make the detection. Wire Service, The Mercury News, "‘Wrecking ball’ of a planet almost avoids discovery because of strange orbit," 28 Aug. 2019 Before, astronomy had been based solely on studies of electromagnetic radiation and exotic particles like neutrinos and cosmic rays. Steve Nadis, Discover Magazine, "We've Found Gravitational Waves. What Will We Learn From Them?," 24 May 2019 Today astronomy is regarded as a science, based on observation, while astrology—the idea that heavenly bodies affect the health and fortunes of people— is not. National Geographic, "Copernicus's revolutionary ideas reorganized the heavens," 9 Apr. 2019 To get the answer, the UCL team turned to one of the great workhorses of modern astronomy, the Hubble Space Telescope. Jeffrey Kluger, Time, "Why This Earth-Like Planet is a Big Step Forward in the Search for Life," 11 Sep. 2019

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'astronomy.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of astronomy

12th century, in the meaning defined above

History and Etymology for astronomy

Middle English astronomie, from Anglo-French, from Latin astronomia, from Greek, from astr- + -nomia -nomy

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Time Traveler for astronomy

Time Traveler

The first known use of astronomy was in the 12th century

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Statistics for astronomy

Last Updated

12 Nov 2019

Cite this Entry

“Astronomy.” The Dictionary, Merriam-Webster Inc., Accessed 22 November 2019.

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More Definitions for astronomy


How to pronounce astronomy (audio)

English Language Learners Definition of astronomy

: the scientific study of stars, planets, and other objects in outer space


as·​tron·​o·​my | \ ə-ˈsträ-nə-mē How to pronounce astronomy (audio) \

Kids Definition of astronomy

: a science concerned with objects and matter outside the earth's atmosphere and of their motions and makeup

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More from Merriam-Webster on astronomy

Rhyming Dictionary: Words that rhyme with astronomy

Spanish Central: Translation of astronomy

Nglish: Translation of astronomy for Spanish Speakers

Britannica English: Translation of astronomy for Arabic Speakers Encyclopedia article about astronomy

Comments on astronomy

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not agreeing with established beliefs

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