* Luminosity and Temperature: A star's luminosity (brightness) is directly related to its temperature. The hotter a star is, the more energy it radiates per unit area, and the brighter it appears.
* Radiation: Stars emit light and energy through nuclear fusion in their core. Hotter stars fuse hydrogen into helium at a much faster rate, producing more energy and radiating more light.
* Wien's Displacement Law: This law states that the peak wavelength of light emitted by a blackbody (approximation of a star) is inversely proportional to its temperature. Hotter stars emit more light at shorter wavelengths, meaning they appear bluer and brighter.
In summary: As main sequence stars get hotter, their increased energy output and peak emission at shorter wavelengths lead to a significant increase in their brightness.
