Both of these are subclasses of the broader category, main sequence stars ... and Henry Norris Russell – independently made a ...

leading to a state of equilibrium between gravitational collapse and the energy released during fusion Key fact In a main sequence star, hydrogen nuclei fuse together to form helium nuclei.

Pairing the known age of a white dwarf with the variable age of a main sequence star allows for more straightforward calculations of important parameters like the relationship between a star's age ...