A substellar object with insufficient mass (typically 13-80 Jupiter masses) to sustain stable hydrogen fusion in its core, occupying the boundary between planets and stars. These 'failed stars' can briefly fuse deuterium when young but gradually cool and dim over billions of years.
Coined by astronomer Jill Tarter in 1975, combining 'brown' (referring to their predicted cool, dim appearance) with 'dwarf' (indicating small stellar objects). The color term was somewhat arbitrary, as these objects actually appear more red or magenta in infrared observations.
Brown dwarfs are the universe's ultimate underachievers! They're too big to be planets but too small to be stars, stuck in cosmic limbo where they slowly fade away over trillions of years - longer than the current age of the universe - making them potential survivors long after all real stars have died.
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