Why are stars called main sequence?
1 Answer
They follow the trend line on the Hertz-Russell Diagram.
Explanation:

Most stars follow the main sequence, with bright stars being hot and cool stars being dim. There are a few exceptions, however, the most notable being White Dwarfs, Giants, and Supergiants.
Read more about the HR Diagram here , here, and [here.](http://oneminuteastronomer.com/808/hr-diagram/)
Read more about the Main Sequence here and [here.](https://en.wikipedia.org/wiki/Main_sequence)
Read more about stars in general [here.](http://science.nasa.gov/astrophysics/focus-areas/how-do-stars-form-and-evolve/)
