Here's why:
* Low Luminosity: Red dwarfs are the smallest and coolest type of main sequence star. They have very low luminosities, meaning they emit very little light and energy. This places them low on the H-R diagram's vertical axis (luminosity).
* Low Temperature: Red dwarfs have surface temperatures of around 2,400 - 3,700 Kelvin, which is much cooler than our Sun. This places them on the right side of the H-R diagram's horizontal axis (temperature).
Therefore, their low luminosity and low temperature position them in the lower right corner of the H-R diagram.
