astronomical unit

noun

Definition of astronomical unit

: a unit of length used in astronomy equal to the mean distance of the earth from the sun or about 93 million miles (150 million kilometers)

Examples of astronomical unit in a Sentence

Recent Examples on the Web In this system, the two inner stars, GW Ori A and B, orbit each other at a distance from Earth to the sun, called an AU or astronomical unit. Ashley Strickland, CNN, "Tatooine-like exoplanet could be orbiting in this triple-star system," 3 Sep. 2020 One astronomical unit is equal to the distance between the Earth and the sun. Ashley Strickland, CNN, "'Waterfalls' of gas reveal baby planets, study says," 16 Oct. 2019 The research team mapped the structure of a newborn star system called L1527, which has only 0.18 times the mass of the sun but whose surrounding envelope of gas stretches to more than 1,000 astronomical units (AU). Sarah Lewin Frasier, Scientific American, "Astronomers Spy Dusty "Traffic Jam" in Young Star System," 14 Feb. 2017 Voyager 1 hit the boundary at about 122 astronomical units from the Sun (an AU is the average distance from the Earth to the Sun); Voyager 2 hit it at 119 AU. John Timmer, Ars Technica, "A bonanza of data from the second Voyager to reach the Solar System’s edge," 4 Nov. 2019 The gaps are located at 87, 140 and 237 astronomical units from their host star. Ashley Strickland, CNN, "'Waterfalls' of gas reveal baby planets, study says," 16 Oct. 2019 The previous record holder orbited the sun at about 120 AU (one AU, or astronomical unit, is the distance from the Earth to the sun). David Grossman, Popular Mechanics, "Move Over, Farout: FarFarOut Has Been Discovered," 25 Feb. 2019 At an orbital distance of 600 astronomical units (1 AU is the distance between Earth and the sun), Planet Nine would be 160,000 times dimmer than Neptune is at 30 AU. Quanta Magazine, "Why Can’t We Find Planet Nine?," 3 July 2018 Farout orbits the sun at about 120 astronomical units (AU)—in other words, 120 times as far from the sun as Earth is. Avery Thompson, Popular Mechanics, "Scientists Find the Most Distant Solar System Object Yet," 17 Dec. 2018

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'astronomical unit.' 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 astronomical unit

1848, in the meaning defined above

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The first known use of astronomical unit was in 1848

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Last Updated

11 Sep 2020

Cite this Entry

“Astronomical unit.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/astronomical%20unit. Accessed 29 Oct. 2020.

More from Merriam-Webster on astronomical unit

Britannica.com: Encyclopedia article about astronomical unit

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