Knowra Red giant Red giant A luminous, cool star that has expanded after exhausting hydrogen in its core. It is a later stage of stellar evolution, powered chiefly by nuclear reactions in shells around the core.
Hydrogen shell burning : Fusion of hydrogen in a layer surrounding a star’s exhausted, helium-rich core. This shell supplies energy as the inert core contracts and the star’s outer layers expand.
Main sequence : The band on the Hertzsprung–Russell diagram where stars spend most of their lives fusing hydrogen in their cores. A star typically becomes a red giant after leaving this long-lived stage.
Red dwarf : A small, cool, low-mass star that fuses hydrogen slowly in its core. Red dwarfs are faint and compact, unlike the luminous, expanded red giants.
Aldebaran : An orange giant star in the constellation Taurus, about 65 light-years from Earth. It is a nearby example of a cool, luminous giant.
Helium flash : A rapid onset of helium fusion in the degenerate core of a low-mass star. It marks the transition from the red-giant branch to stable helium burning in low-mass stars.
Stellar nucleosynthesis : The production of chemical elements through nuclear reactions inside stars and stellar explosions. Red-giant fusion builds some heavier elements and alters the star’s composition.
Red supergiant : An extremely large, luminous evolved star that has exhausted core hydrogen and has a high-mass progenitor. Red supergiants are a massive-star counterpart, not simply ordinary red giants at greater size.
Arcturus : A bright orange giant star in the constellation Boötes, about 37 light-years from Earth. Its brightness and color make it a prominent example of a red giant.
Triple-alpha process : A sequence of nuclear reactions that fuses three helium-4 nuclei into carbon-12. This process powers the core after a low-mass red giant ignites helium.
Stellar luminosity : The total energy a star radiates per unit time. Red giants radiate strongly despite having relatively cool surfaces, because their radiating areas are enormous.
Show all 21