What state defines the long, stable phase when a star officially settles onto the main sequence?

Answer

Hydrostatic equilibrium

This state is achieved when the outward thermal pressure generated by core fusion perfectly counteracts the inward crushing force exerted by gravity.

What state defines the long, stable phase when a star officially settles onto the main sequence?

#Videos

Birth of a star - from nebula to main sequence - YouTube

sequencestarnebulaformation