* Luminosity and Temperature: A star's luminosity (brightness) is directly related to its surface temperature. The hotter the star, the more energy it radiates, and the brighter it appears.
* Main Sequence: Main sequence stars are fusing hydrogen into helium in their cores. The rate of this fusion reaction is directly dependent on the star's mass. More massive stars have higher core temperatures and pressures, leading to faster fusion and higher luminosity.
* The Hertzsprung-Russell Diagram: The relationship between luminosity and temperature for main sequence stars is clearly shown on the Hertzsprung-Russell (H-R) diagram. Stars on the main sequence form a diagonal band, with hotter, brighter stars located towards the upper left corner.
In summary: The higher the mass of a main sequence star, the hotter its core, the faster its fusion reactions, and the brighter and hotter it will appear.
