Luminosity classes

Definition

Luminosity classes are categories in the classification of stars based on their luminosity, which is related to their size and stage in the stellar evolutionary process. These classes help astronomers determine a star's true brightness and distance from Earth.

5 Must Know Facts For Your Next Test

1. Luminosity classes range from I (supergiants) to V (main-sequence stars).
2. The Sun is classified as a G2V star, with 'V' indicating it is a main-sequence star.
3. The H–R Diagram plots stars based on their luminosity class and spectral type.
4. Luminosity class helps in determining the absolute magnitude of stars, which is crucial for measuring cosmic distances.
5. Supergiants (Class I) are much brighter and larger than main-sequence stars (Class V), but they have shorter lifespans.

Review Questions

• What does a luminosity class tell us about a star?
• How does the H–R Diagram utilize luminosity classes?
• Why are luminosity classes important for measuring cosmic distances?

Related terms

H–R Diagram: A graph that plots stars according to their absolute magnitude and spectral type.

Spectral Type: A classification system for stars based on their temperature and light spectrum.

Absolute Magnitude: The measure of intrinsic brightness of a celestial object, independent of its distance from Earth.