arc second


Examples of arc second in a Sentence

Recent Examples on the Web Their sky brightness must routinely be 21.5 magnitudes per square arc second or darker—in comparison, a theoretically perfect dark site would have a brightness of 22, while a city with a very polluted light sky could measure around 16 or 17. Margaret Osborne, Smithsonian Magazine, 24 Feb. 2023 The night sky brightness must typically be equal to or darker than 21.2 magnitudes per square arc second. Stacey Leasca, Travel + Leisure, 6 May 2021 Hubble has a diameter of 2.4 meters, which gives a resolution of 0.13 arc second for observations at a one-micron wavelength. Meredith A. MacGregor, Scientific American, 19 May 2020

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'arc second.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

First Known Use

1885, in the meaning defined above

Time Traveler
The first known use of arc second was in 1885

Dictionary Entries Near arc second

Cite this Entry

“Arc second.” Dictionary, Merriam-Webster, Accessed 8 Dec. 2023.

Love words? Need even more definitions?

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