Knowra Red supergiant Red supergiant A massive, evolved star with a cool surface, enormous radius, and high luminosity. It has exhausted hydrogen in its core and expanded as it fuses heavier elements in shells.
Stellar evolution : The sequence of physical changes a star undergoes from formation through its final remnant or dispersal. Red supergiants are a late stage in the evolution of massive stars.
Stellar mass : The amount of matter contained in a star, usually expressed relative to the Sun's mass. High initial mass determines whether a star can evolve into a red supergiant.
Betelgeuse : A nearby red supergiant in Orion that varies in brightness and is among the largest familiar stars. Its changing brightness and resolved surface make it a prominent nearby example.
Blue supergiant : A massive, luminous star with a hot, blue surface, often in a relatively brief evolved phase. Its high surface temperature contrasts with the cool, expanded envelope of a red supergiant.
Stellar wind : A continuous outflow of particles from a star into its surrounding space. Red supergiants shed substantial material through slow, dense winds.
Hydrogen burning : The fusion of hydrogen nuclei into helium, which supplies energy in most stars. Exhausting central hydrogen ends the main-sequence stage before the star expands.
Stellar radius : The distance from a star's center to its photosphere, the layer from which most visible light escapes. Red supergiants have exceptionally large radii compared with the Sun.
Antares : A bright red supergiant in the constellation Scorpius, among the most luminous stars visible to the naked eye. Its large apparent size allows detailed study of a red-supergiant atmosphere.
Yellow hypergiant : A rare, extremely luminous evolved star with a yellow surface and strong mass loss. It occupies a hotter, unstable regime than the typical red-supergiant state.
Circumstellar medium : Gas and dust surrounding a star, often formed or altered by its outflows. Ejected red-supergiant material can surround the star before it explodes.
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