How does a star's spectral class relate to its temperature and luminosity?

A star's spectral class is directly related to its temperature and luminosity.

The spectral class of a star is determined by its surface temperature, which in turn affects its luminosity. The temperature of a star is determined by the amount of energy it emits, with hotter stars emitting more energy than cooler ones. This energy is emitted in the form of light, and the spectrum of this light can be used to determine a star's spectral class.

The spectral class of a star is denoted by a letter, with the hottest stars being classified as O and the coolest as M. The temperature range for each spectral class is as follows: O (30,000-50,000 K), B (10,000-30,000 K), A (7,500-10,000 K), F (6,000-7,500 K), G (5,200-6,000 K), K (3,700-5,200 K), and M (2,400-3,700 K).

The luminosity of a star is also related to its temperature, with hotter stars being more luminous than cooler ones. This is because hotter stars emit more energy, which in turn makes them brighter. The luminosity of a star is measured in terms of its absolute magnitude, which is a measure of the amount of light it emits.

Overall, a star's spectral class is a useful way to determine its temperature and luminosity. By analysing the spectrum of a star's light, astronomers can gain valuable insights into its physical properties and evolutionary history.