subgiant star

astronomy

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July 14, 2026

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A subgiant star is a star that falls above the main sequence on the spectrum-luminosity diagram but below the region of ordinary giant stars. These stars represent a stage in stellar evolution after a star leaves the main sequence. As a star evolves, its future path is determined by its mass, rotation rate, and chemical composition.123

In low-mass stars, after exhausting hydrogen in their core, they begin to fuse helium. This process causes the star to become more luminous and expand, moving towards the giant domain on the Hertzsprung-Russell diagram. Subgiants are redder and larger than main-sequence stars of the same luminosity. Many well-known examples are found in close binary systems.23

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Hertzsprung-Russell diagram
Subgiants are stars that are redder and larger than main-sequence stars of the same luminosity. Many of the best-known examples are found in close binary systems where conditions favour their detection.
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Subgiants are stars that are redder and larger than main-sequence stars of the same luminosity. Many of the best-known examples are found in close binary systems where conditions favour their detection.
Read More