Definition
A star is a luminous sphere of plasma bound together by its own gravity. In its core, pressure and temperature are high enough to drive nuclear fusion, which releases the energy that makes the star shine.
In context
Stars vary enormously in mass, temperature, and color, and a star's mass largely sets how it lives and how it ends. Our Sun is a fairly typical star and the closest one to Earth, which is why it appears so much brighter than any other.
Related ideas
Stars gather by the billions into galaxies. When some massive stars die they explode as supernovae, and the most massive can leave behind black holes.
Related entries
Encyclopedia
Galaxy
A gravitationally bound system of stars, gas, dust, and dark matter.
Encyclopedia
Supernova
The explosive death of certain stars.
Encyclopedia
Light-Year
The distance light travels in one year — a measure of distance.
Encyclopedia
Planet
A round body that orbits the Sun and has cleared its orbit.