Summary:
- The most common way of classifying main sequence stars is by color (Table below) Each class of star is given a letter, a color, and a range of temperatures.
- The hotter a main sequence star is, the brighter it is.
- A star remains on the main sequence as long as it is fusing hydrogen to form helium.
- Bigger stars produce more energy, so their surfaces are hotter.
- But some very small stars are very hot.
- Some very big stars are cool.
- Large stars burn through their supply of hydrogen very quickly.