Main Sequence
The continuous evolutionary diagonal band on the Hertzsprung-Russell diagram containing stars fusing hydrogen into helium in their cores.
Governing formula
L ∝ M^3.5 (Mass-Luminosity Relation)
SI unit
H-R Diagram Band
In depth
Stars spend ~90% of their operational lifetime on the main sequence in hydrostatic equilibrium balancing inward gravity with outward radiation pressure. Mass dictates core temperature, luminosity, and main sequence lifespan.
Examples in the real world
Our Sun residing on the main sequence for a total lifetime of ~10 billion years.