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

A research team led by University of California San Diego Professor of Astronomy and Astrophysics Adam Burgasser has now detected phosphine in the atmosphere of a cool, ancient brown dwarf known as Wolf 1130C.

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"Prior to JWST, phosphine was expected to be abundant in exoplanet and brown dwarf atmospheres, following theoretical predictions based on the turbulent mixing we know exists in these sources," explained co-author Sam Beiler, a postdoctoral scholar at Trinity College Dublin who recently earned his doctorate from the University of Toledo.

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The discovery raises a new question: why does this particular brown dwarf contain phosphine while others do not?

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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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