• synonyms


  1. the region of the upper atmosphere in which temperature increases continuously with altitude, encompassing essentially all of the atmosphere above the mesosphere.
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Origin of thermosphere

First recorded in 1950–55; thermo- + sphere
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for thermosphere

Historical Examples

  • They were piercing the thermosphere where the outside temperature gradient would zoom upward toward the 2,000 degree mark.

    First on the Moon

    Jeff Sutton

British Dictionary definitions for thermosphere


  1. an atmospheric layer lying between the mesosphere and the exosphere, reaching an altitude of about 400 kilometres where the temperature is over 1000°C
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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 thermosphere


1924, from thermo- + sphere.

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Online Etymology Dictionary, © 2010 Douglas Harper

thermosphere in Science


  1. The region of the Earth's upper atmosphere lying above the mesosphere and extending from a height of approximately 80 km (50 mi) to between 550 and 700 km (341 and 434 mi) above the Earth's surface. In the thermosphere temperatures increase steadily with altitude, reaching as high as 1,727°C (3,140°F) at the highest elevations. Chemical reactions occur much faster here than on the surface of the Earth. See also exosphere mesosphere stratosphere troposphere. See illustration at atmosphere.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.