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Why Do Stars Die?

AstronomyAstrophysics

Quick Answer

Stars die when they exhaust the nuclear fuel in their cores — without the outward radiation pressure from fusion to counterbalance gravity, the core collapses, triggering the star final stage.

The Full Story

A star life is a battle between gravity pulling inward and radiation pressure from nuclear fusion pushing outward. Main-sequence stars fuse hydrogen into helium in their cores for millions to billions of years. When hydrogen fuel runs low, the core contracts and heats up, igniting helium fusion (and heavier elements in massive stars) in successive shells. Low-mass stars like the Sun eventually shed their outer layers as a planetary nebula, leaving a white dwarf. Stars above about 8 solar masses undergo iron core collapse — since iron fusion absorbs rather than releases energy, the core suddenly has no outward pressure, collapses in milliseconds, and rebounds in a supernova explosion, leaving a neutron star or black hole. The heaviest elements (gold, platinum, uranium) are forged in these cataclysmic final moments.

Key Facts

1.The Sun has about 5 billion years of hydrogen fuel remaining before it expands into a red giant and eventually becomes a white dwarf.
2.A supernova can briefly outshine an entire galaxy of hundreds of billions of stars, releasing more energy in seconds than the Sun will in its entire 10-billion-year lifetime.
3.Neutron stars are so dense that a teaspoonful of neutron star material would weigh about 6 billion tonnes on Earth.

YouTube Angle

Suggested video title for this topic:

"How Stars Die — From Red Giants to Supernovae"