• synonyms


  1. a sphere of light or radiance.
  2. Astronomy. the luminous visible surface of the sun, being a shallow layer of strongly ionized gases.
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Origin of photosphere

First recorded in 1655–65; photo- + -sphere
Related formspho·to·spher·ic [foh-tuh-sfer-ik, -sfeer-] /ˌfoʊ təˈsfɛr ɪk, -ˈsfɪər-/, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for photosphere

Historical Examples

  • It is from the photosphere, as has been said, that we have won most of our knowledge of the sun.

    The Outline of Science, Vol. 1 (of 4)

    J. Arthur Thomson

  • The dazzling surface of this globe is called a photosphere (light sphere).

    Astronomy for Amateurs

    Camille Flammarion

  • The part of the Sun that we see is its luminous surface, or photosphere.

    Astronomy for Amateurs

    Camille Flammarion

  • Only the photosphere may be to a greater or less extent solid or liquid.

  • Dark spots of a deep bluish black will often be seen on the photosphere of the sun.


    David Todd

British Dictionary definitions for photosphere


  1. the visible surface of the sun, several hundred kilometres thick
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Derived Formsphotospheric (ˌfəʊtəʊˈsfɛrɪk), adjective
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for photosphere


1660s, "orb of light," from photo- + -sphere. Astronomical sense is from 1848.

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Online Etymology Dictionary, © 2010 Douglas Harper

photosphere in Science


  1. The lowest visible layer of a star, lying beneath the chromosphere and the corona. Stars are made entirely of gas and thus have no surface per se, but the gas beneath the photosphere is opaque, so the photosphere acts as their effective visible surface; it is also the boundary from which the Sun's diameter is measured. The Sun's photosphere is a very thin layer made up of numerous granules (transient convective cells) where hot gases rise and give off light and heat. The photosphere of the Sun has a temperature of around 6,000°K and is the region in which sunspot activity is located.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.