Question

Hundreds, even thousands of stars may be easily observed in the night sky. What process produces the light from the stars?

A.
radioactive decay of heavy elements
B.
gravitational waves, released by the high mass of stars
C.
chemical combustion of hydrogen
D.
nuclear fusion, in which atomic nuclei combine

Answer 1

D. nuclear fusion, in which atomic nuclei combine

Stars shine because in their hot, dense cores hydrogen nuclei fuse into helium (mainly via the proton–proton chain or CNO cycle). A small amount of mass is converted to energy (E = mc²), emitted as photons. Radioactive decay and chemical burning are far too weak to power a star, and gravitational waves are not a significant energy source.