The great spread in luminosities and colours of giant, supergiant, and subgiant stars is also understood to result from evolutionary events. When a star leaves the main sequence, its future evolution is precisely determined by its mass, rate of rotation (or angular momentum), and chemical composition and whether it is a member of a close binary system. Giants and supergiants of nearly the same radius and surface temperature may have evolved from main-sequence stars of different ages and masses.
Embryonic-stars-in-the-Eagle-Nebula-This-detail-of-aEmbryonic stars in the Eagle Nebula (M16, NCG 6611)[Credits : Photo AURA/STScI/NASA/JPL (NASA photo # STScI-PRC95-44b)]
Light-curve-of-Algol-an-eclipsing-variable-or-eclipsing-binaryLight curve of Algol (Beta Persei), an eclipsing variable, or eclipsing binary, star system. The …[Credits : Encyclopædia Britannica, Inc.]
Schematic-spectrum-luminosity-correlation-of-spiral-arm-stars-in-theSchematic spectrum–luminosity correlation (Hertzsprung–Russell diagram) of spiral-arm …[Credits : From Astrophysical Journal, reproduced by permission of the American Astronomical Society]
Colour-magnitude-diagram-for-an-old-globular-cluster-made-upColour-magnitude (Hertzsprung-Russell) diagram for an old globular cluster made up of Population II …[Credits : From Astrophysical Journal, reproduced by permission of the American Astronomical Society]
Eta-CarinaeEta Carinae.[Credits : Photo AURA/STScI/NASA/JPL (NASA photo # STScI-PRC96-23a)]
N81-and-new-stars-observed-by-the-Hubble-Space-TelescopeN81 and new stars, observed by the Hubble Space Telescope.[Credits : Photo AURA/STScI/NASA/JPL (NASA photo # STScI-PR98-25)]
Centre-of-the-Orion-Nebula-Astronomers-have-identified-some-700Centre of the Orion Nebula (M42).[Credits : Photo AURA/STScI/NASA/JPL (NASA photo # STScI-PRC95-45a)]
Stellar-parallaxFigure 3: Stellar parallax[Credits : Encyclopædia Britannica, Inc.]
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