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

Image: The picture shows an artist's recreation of the orbital paths of both brown dwarf stars, in blue, and of the unusually orbiting planet, in orange.

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After carefully studying its dance routine, astronomers think that the white dwarf has a partner, probably another dead star or a brown dwarf.

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Published in the journal Nature, the findings suggest that this brown dwarf might generate aurorae similar to those seen on our own planet as well as on Jupiter and Saturn.

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W1935 is a cold brown dwarf with a surface temperature of about 400° Fahrenheit, or about the temperature at which you'd bake chocolate chip cookies.

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After looking at a number of brown dwarfs observed with JWST, Faherty's team noticed that W1935 looked similar but with one striking exception: it was emitting methane, something that's never been seen before on a brown dwarf.

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