H–R diagram

Definition

The H–R diagram, or Hertzsprung-Russell diagram, is a scatter plot of stars showing the relationship between their absolute magnitudes or luminosities versus their stellar classifications or effective temperatures. It is a fundamental tool in understanding stellar evolution and properties.

5 Must Know Facts For Your Next Test

1. The H–R diagram categorizes stars into main sequence, giants, supergiants, and white dwarfs.
2. Stars spend most of their lifetimes on the main sequence of the H–R diagram.
3. The position of a star on the H–R diagram provides information about its luminosity and temperature.
4. As stars evolve, they move off the main sequence and can become red giants or white dwarfs.
5. The H–R diagram is crucial for determining distances to stars using methods like spectroscopic parallax.

Review Questions

• What are the four primary regions where stars are located on the H–R diagram?
• How does a star's position on the H–R diagram change as it evolves from the main sequence to a red giant?
• Why is the H–R diagram important for measuring cosmic distances?

Related terms

Main Sequence: A continuous and distinctive band of stars that appears on plots of stellar color versus brightness.

Red Giant: A luminous giant star in a late phase of stellar evolution; it has exhausted hydrogen in its core.

White Dwarf: A small, dense star that represents the final evolutionary state of stars not massive enough to become neutron stars or black holes.