brown dwarf

[ broun dwawrf ]

noun

, Astronomy.

1. 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.

brown dwarf

noun

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

brown dwarf

1. 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.
2. See Note at dwarf star

Word History and Origins

Origin of brown dwarf¹

First recorded in 1975–80

Example Sentences

Below this temperature, though, “it’s all brown dwarfs,” Hsu says.

From Science News

In contrast, brown dwarfs glow red primarily from the heat of their birth, but then their nuclear activity sputters out, causing them to cool and fade.

From Science News

Dupuy says additional red and brown dwarfs should be observed to verify the finding.

From Science News

This is the temperature that a new study says separates red dwarf stars, which shine for a long time, from failed stars known as brown dwarfs.

From Science News

So the world was astounded when, in October 1995, Mayor and his student Didier Queloz reported strong evidence not of a brown dwarf, but of a true planet orbiting the sunlike star 51 Pegasi, about 50 light-years from our solar system.

From Science News

They passed out by the big gate and caught sight of the brown dwarf on the parapet of the stockade.

From Project Gutenberg

On the parapet, in his old place, the brown dwarf squatted, expressionless as the Sphinx.

From Project Gutenberg

At the first collision we saw a big ant fall upon a brown dwarf, and annihilate it at one blow.

From Project Gutenberg