Period-luminosity relation

Definition

The period-luminosity relation is a direct relationship between the pulsation period of a variable star and its intrinsic luminosity. This principle is instrumental in determining cosmic distances.

5 Must Know Facts For Your Next Test

1. The period-luminosity relation was first discovered by Henrietta Swan Leavitt in 1908.
2. Cephied variables are the primary type of stars used to establish this relation.
3. The longer the pulsation period of a Cepheid variable, the more luminous it is.
4. This relation helps astronomers measure distances to galaxies far beyond our own Milky Way.
5. By comparing apparent brightness and intrinsic luminosity, astronomers can calculate the distance to Cepheid variables using the distance modulus formula.

Review Questions

• What type of stars are primarily used to apply the period-luminosity relation?
• Who discovered the period-luminosity relation and when?
• How does knowing a variable star's pulsation period help determine its distance from Earth?

Related terms

Cepheid Variable: A type of star that pulsates radially with a well-defined stable period and amplitude, crucial for establishing the period-luminosity relation.

Intrinsic Luminosity: The inherent brightness of a celestial object, not affected by distance or interstellar material.

Distance Modulus: A formula used to calculate astronomical distances incorporating apparent magnitude and absolute magnitude.