Main-sequence stars

Definition

Main-sequence stars are stars that are in the longest, stable phase of their life cycle, during which they fuse hydrogen into helium in their cores. They are plotted along a continuous and distinctive band on the Hertzsprung-Russell (H–R) diagram.

5 Must Know Facts For Your Next Test

1. Main-sequence stars occupy the diagonal band from the upper left (hot, luminous stars) to the lower right (cool, dim stars) on the H–R diagram.
2. The Sun is a typical example of a main-sequence star.
3. These stars generate energy through nuclear fusion of hydrogen into helium in their cores.
4. The mass of a main-sequence star determines its position on the H–R diagram: higher mass stars are hotter and more luminous.
5. Main-sequence lifetimes vary; high-mass stars exhaust their fuel quickly and have shorter lifespans compared to low-mass stars.

Review Questions

• What process powers main-sequence stars?
• Where do main-sequence stars appear on the H–R diagram?
• How does the mass of a main-sequence star affect its lifespan?

Related terms

Hertzsprung-Russell Diagram: A graphical tool that plots stars according to their luminosity and temperature.

Nuclear Fusion:

The process by which nuclei of small atoms combine to form a new, more massive nucleus; releases energy.

Red Giant:

A late-stage star that has exhausted hydrogen in its core and expanded significantly while cooling down.