red giant

American  

noun

Astronomy.

1. a star in an intermediate stage of evolution, characterized by a large volume, low surface temperature, and reddish hue.

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red giant British  

noun

1. a giant star towards the end of its life, with a relatively low temperature of 2000–4000 K, that emits red light

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red giant Scientific  

1. A giant star that has a relatively low surface temperature, giving it a reddish or orange hue. Red giants are non-main-sequence stars positioned in the upper right of the Hertzsprung-Russell diagram. They are not massive stars but rather late, expanded stages of lower-mass main-sequence stars that have exhausted the hydrogen in their core and are fusing their remaining hydrogen into helium in a luminous outer shell. The Sun is expected to become a red giant in about 5 billion years, expanding to 70 times its current size and bringing its surface extremely close to Earth's present orbit.

2. See more at star See Note at dwarf star

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Etymology

Origin of red giant

First recorded in 1915–20

Example Sentences

These include Cepheid variable stars, which brighten and dim in predictable ways, red giant stars with known brightness, Type Ia supernovae, and certain galaxy types.

From Science Daily • Apr. 12, 2026

One possibility is that the signal comes from a red giant star, while another idea is that it could be a fading light echo related to the burst itself.

From Science Daily • Mar. 15, 2026

R Doradus is a red giant star located about 180 light years from Earth in the southern constellation Dorado, also known as the Swordfish.

From Science Daily • Jan. 12, 2026

A small white dwarf, which is a dead star, is locked in a cosmic dance with a much larger red giant - a star that's reaching the end of its life.

From BBC • Dec. 30, 2024

When the Sun, ruddy and bloated, becomes a red giant, it will envelop and devour the planets Mercury and Venus—and probably the Earth as well.

From "Cosmos" by Carl Sagan