Explore star classification by temperature and luminosity.
The Hertzsprung-Russell diagram plots stars by surface temperature (x, decreasing right) vs luminosity (y, increasing up). The main sequence runs diagonally — hot, luminous blue stars (top-left) to cool, dim red dwarfs (bottom-right). Giants and supergiants sit above; white dwarfs below. A star's position changes as it evolves through its lifecycle.