brown dwarves

brown dwarf

noun Astronomy.
a cold, dark star that is too small to initiate the nuclear reactions that generate heat and light.
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World English Dictionary
brown dwarf
 
n
a type of celestial body midway in mass between a large planet and a small star

Collins English Dictionary - Complete & Unabridged 10th Edition
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Science Dictionary
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.
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