Yellow hypergiant

Intrinsic variable types in the Hertzsprung–Russell diagram showing the Yellow Hypergiants above (i.e. more luminous than) the Cepheid instability strip.

A yellow hypergiant is a huge hypergiant star. It starts off a mass of about 20–60 solar masses, but it soon loses about half that mass (because they are very unstable). It has a spectral class from A to K.

They are amongst the most luminous stars, with absolute magnitude (M_V) around −9. They are very rare: only 15 are known in the Milky Way and six of those are in a single cluster.

They are sometimes referred to as 'cool hypergiants' in comparison to O- and B-type stars, and sometimes as 'warm hypergiants' in comparison to red supergiants. Yellow hypergiants have evolved off the main sequence and have little hydrogen left in their centres.

Examples

• Rho Cassiopeiae
• V509 Cassiopeiae
• V382 Carinae
• HR 5171

Yellow Hypergiant Media

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  Visual light curve for ρ Cassiopeiae from 1933 to 2015

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  IRAS 17163-3907 is a yellow hypergiant that clearly shows the expelled material that probably surrounds all yellow hypergiants.

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  Yellow hypergiant HR 5171 A, seen as the bright yellow star at the center of the image.

• Artist's impression of the binary system containing yellow hypergiant HR 5171 A