brown dwarf

[ broun-dwawrf ]
/ ˈbraʊn ˈdwɔrf /

noun Astronomy.

a celestial object smaller than a small star but larger than a giant planet: believed to form as stars do, from collapsing clouds of gas and dust, brown dwarfs are sometimes called failed stars as they are not dense enough to initiate nuclear fusion, leaving them much dimmer and cooler than stars.

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Origin of brown dwarf

First recorded in 1975–80
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2020

British Dictionary definitions for brown dwarf

brown dwarf

noun

a type of celestial body midway in mass between a large planet and a small star
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

Scientific definitions for brown dwarf

brown dwarf

A celestial body with insufficient mass to sustain the nuclear fusion that produces radiant energy in normal stars. It is believed that a brown dwarf is formed with enough mass to start nuclear fusion in its core, but without enough for the fusion to become self-sustaining. Theory suggests that a body with about one percent of the mass of the Sun-or ten times the mass of Jupiter-can generate this initial fusion, but that it needs at least eight percent of the Sun's mass to sustain the fusion. After the fusion ends, the dwarf still glows for a period from radiating heat, with a surface temperature of about 2,500°K (4,532°F) or less. See Note at dwarf star.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.