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单词 red giant
释义
red giant

Physics
  • A giant star thought to be in the later stages of stellar evolution. It has a surface temperature in the range 2000–3000 K and a diameter 10–100 times that of the sun. See also death of a star; Hertzsprung–Russell diagram.


Astronomy
  • A cool, large, and highly luminous star. Red giants are stars that have left the main sequence, having exhausted the hydrogen fuel in their cores, and are powered by nuclear reactions between elements heavier than hydrogen. They owe their colour to their cool surface temperatures (below 4000 K, spectral type K or M). Because of their large diameters, 25 times that of the Sun or more, they are highly luminous, many hundreds of times that of the sun. Massive main-sequence stars may evolve into red giants after passing through a blue-giant phase, while lower-mass stars, such as the Sun, will evolve directly into a red giant. Many red giants are pulsating variable stars.


Space Exploration
  • Any large bright star with a cool surface. It is thought to represent a late stage in the evolution of a star like the Sun, as it runs out of hydrogen fuel at its centre and begins to burn heavier elements, such as helium, carbon, and silicon. Because of more complex nuclear reactions that then occur in the red giant's interior, it eventually becomes gravitationally unstable and begins to collapse and heat up. The result is either explosion of the star as a supernova, leaving behind a neutron star, or loss of mass by more gradual means to produce a white dwarf.

    Red giants have diameters between 10 and 100 times that of the Sun. They are very bright because they are so large, although their surface temperature is lower than that of the Sun, about 2 000–3 000 K (1 700–2 700 °C).


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