What is a Star?
Part of Hall of the Universe.
![What is a star_HERO](/var/ezflow_site/storage/images/media/amnh/images/exhibitions/permanent-exhibitions/rose-center-for-earth-and-space/hall-of-the-universe2/calder/hou-hero-images/what-is-a-star_hero/1049045-1-eng-US/what-is-a-star_hero_wideexact_2460.jpg 2460w,/var/ezflow_site/storage/images/media/amnh/images/exhibitions/permanent-exhibitions/rose-center-for-earth-and-space/hall-of-the-universe2/calder/hou-hero-images/what-is-a-star_hero/1049045-1-eng-US/what-is-a-star_hero_wideexact_1230.jpg 1230w,/var/ezflow_site/storage/images/media/amnh/images/exhibitions/permanent-exhibitions/rose-center-for-earth-and-space/hall-of-the-universe2/calder/hou-hero-images/what-is-a-star_hero/1049045-1-eng-US/what-is-a-star_hero_wideexact_800.jpg 800w,/var/ezflow_site/storage/images/media/amnh/images/exhibitions/permanent-exhibitions/rose-center-for-earth-and-space/hall-of-the-universe2/calder/hou-hero-images/what-is-a-star_hero/1049045-1-eng-US/what-is-a-star_hero_wideexact_400.jpg 400w)
An ordinary star is a massive sphere of luminous gas, mainly hydrogen and helium. A star’s heat and light derive from nuclear fusion in its core. During most of its life, a star is balanced between the inward pressure of its gravity and the outward pressure of its internal heat.
AMNH/D. Finnin