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

Because our Sun will eventually become a red giant, these findings also provide insight into its future evolution.

From Science Daily • Mar. 24, 2026

The red giant is described as "alpha-rich," meaning it contains large amounts of heavy elements that are typically found in very old stars.

From Science Daily • Dec. 26, 2025

These observations show the star completes one full rotation every 398 days, which is unusually fast for a red giant of its age that evolved alone.

From Science Daily • Dec. 26, 2025

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

As the core of a massive red giant collapses to form such a neutron star, it spins faster.

From "Cosmos" by Carl Sagan