red dwarf

American  

noun

Astronomy.

1. any of the faint reddish stars having diameters about half that of the sun and low surface temperatures, about 2000–3000 K; a main sequence star of spectral type M.

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red dwarf British  

noun

1. one of a class of small cool main-sequence stars

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red dwarf Scientific  

1. A small, dim star with relatively cool surface temperatures, positioned to the lower right on the main sequence in the Hertzsprung-Russell diagram. Red dwarfs, at about 0.1 to 0.5 solar mass, consume their nuclear fuel very slowly and live for about 100 billion years. Although they are difficult to see, they are so long-lived that they are likely the most abundant type of star; of the 30 nearest stars to Earth, 21 are red dwarfs, including the closest star, Proxima Centauri.

2. See Note at dwarf star

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Etymology

Origin of red dwarf

First recorded in 1915–20

Example Sentences

There’s a sci-fi podcast called “Wolf 359,” about a crew of a space station circling a red dwarf star.

From Los Angeles Times • Apr. 16, 2026

"While the sun is a bright, yellow dwarf star, TRAPPIST-1 is an ultracool red dwarf, meaning it is significantly smaller, cooler and dimmer than our sun," he explained.

From Science Daily • Dec. 12, 2025

The closest red dwarf to us is Proxima Centauri.

From Space Scoop • Nov. 28, 2025

The star producing the eruption is a red dwarf, which is a much cooler, dimmer, and smaller type of star than the Sun.

From Science Daily • Nov. 14, 2025

“Its orbital period is the same as its rotational period, locked in place by its red dwarf sun.”

From "The Last Cuentista" by Donna Barba Higuera