Main sequence

Definition

The main sequence is a continuous and distinctive band of stars that appears on plots of stellar color versus brightness. Stars spend the majority of their lifetimes in this phase, where they are fusing hydrogen into helium in their cores.

5 Must Know Facts For Your Next Test

1. Stars on the main sequence are in hydrostatic equilibrium, balancing gravitational forces with pressure from nuclear fusion reactions.
2. The position of a star on the main sequence is primarily determined by its mass.
3. Main sequence stars can range from about 0.1 to 100 times the mass of our Sun.
4. The Sun is an example of a main sequence star, specifically classified as a G-type star.
5. As stars exhaust their hydrogen fuel, they leave the main sequence and evolve into red giants or other types of stars.

Review Questions

• What process powers a star while it is on the main sequence?
• How does a star’s mass affect its position on the main sequence?
• What happens to a star after it leaves the main sequence?

Related terms

H–R Diagram: A graphical tool that plots stars according to their luminosity and temperature, revealing patterns like the main sequence.

Red Giant:

A late phase in stellar evolution where a star has exhausted hydrogen in its core and expands significantly.

Hydrostatic Equilibrium:

The balance between gravitational collapse and pressure from nuclear fusion within a star.