astronomical unit


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

Some simple numbers to spell it out: Distance in the solar system is measured in astronomical units (AU), which is the distance between Earth and the sun. John Wenz, Popular Mechanics, "Why Voyager 2 Is In Interstellar Space But Not Out of the Solar System," 13 Dec. 2018 Sedna's elliptical orbit takes it as close to the sun as 76 astronomical units (AU; the Earth-sun distance, about 93 million miles, or 150 million kilometers) and as far away as 936 AU. Nola Taylor Redd,, "No Need for Planet Nine? Small Objects' Gravity Could Explain Weird Orbits," 5 June 2018 At this week’s pass, the asteroid will be about .07 astronomical units or about 6.5 million miles away — the equivalent of about 30 trips between our pale blue planet and the moon. Blaine Friedlander, Washington Post, "The biggest meteor shower of the year peaks tonight. Here’s how to watch.," 13 Dec. 2017 Gliese 710 will be about 16,000 astronomical units away from the sun. Jason Daley, Smithsonian, "2.8 Million Stars Sparkle in This Incredible Image of the Milky Way," 6 Sep. 2017 For instance, the object takes 1,100 earth years to orbit the sun in an elliptical orbit that brings it as close as 38 astronomical units (the distance of the earth to the sun) and as far as 180 AUs. Jason Daley, Smithsonian, "Meet DeeDee, the Solar System’s Newest Dwarf Planet (Maybe)," 14 Apr. 2017

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.

See More

First Known Use of astronomical unit

1848, in the meaning defined above

Keep scrolling for more

Learn More about astronomical unit

Share astronomical unit

Statistics for astronomical unit

Last Updated

18 Feb 2019

Look-up Popularity

Time Traveler for astronomical unit

The first known use of astronomical unit was in 1848

See more words from the same year

More from Merriam-Webster on astronomical unit Encyclopedia article about astronomical unit

Comments on astronomical unit

What made you want to look up astronomical unit? Please tell us where you read or heard it (including the quote, if possible).


of or relating to a parable or parabola

Get Word of the Day daily email!

Test Your Vocabulary

A Green Quiz

  • shamrock
  • What is the best definition of green-eyed monster?
True or False

Test your knowledge - and maybe learn something along the way.


Test Your Knowledge - and learn some interesting things along the way.


Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!