Which part of a star does the star’s energy come from?

For most of its active life, a star shines due to thermonuclear fusion of hydrogen into helium in its core, releasing energy that traverses the star's interior and then radiates into outer space. At the end of a star's lifetime, its core becomes a stellar remnant : a white dwarf , a neutron star , or, if it is sufficiently massive, a black hole .

Explanation:

its nuclear fusion

Explanation:

it is the most commonly accepted one