sentences: the sun is a source of light energy called sunlight & the sun is a source of heat energy called sunlight ->  the sun is a source of light and heat energy  the sun is a source of light and heat energy & a source of something emits / produces / generates / provides that something ->  the sun produces light and heat energy  the sun produces light and heat energy & nuclear reactions are the source of the sun's energy ->  the sun produces light and heat energy through nuclear reactions  the sun produces light and heat energy through nuclear reactions & a star is a source of light / light energy through nuclear reactions -> the sun is a kind of star