Variable star

Definition

A variable star is a star whose brightness as seen from Earth fluctuates over time. These fluctuations can be due to intrinsic properties of the star or extrinsic factors such as eclipses by orbiting bodies.

5 Must Know Facts For Your Next Test

1. Variable stars are crucial for measuring cosmic distances because their luminosity changes in predictable ways.
2. Cepheid variables are a type of variable star used as standard candles to determine distances to far-off galaxies.
3. The period-luminosity relationship in Cepheid variables allows astronomers to calculate their absolute magnitude.
4. RR Lyrae stars are another type of variable star, often found in globular clusters, and are used to measure shorter cosmic distances.
5. The brightness variations of eclipsing binary stars happen due to one star passing in front of the other from our viewpoint on Earth.

Review Questions

• How do Cepheid variable stars help astronomers determine cosmic distances?
• What is the significance of the period-luminosity relationship in Cepheid variables?
• What distinguishes RR Lyrae stars from Cepheid variables?

Related terms

Cepheid Variable: A type of variable star with a well-defined relationship between its luminosity and pulsation period, useful for measuring cosmic distances.

RR Lyrae Star: A type of variable star typically found in globular clusters, used to measure shorter cosmic distances due to their relatively constant period.

Eclipsing Binary Star: A system where two stars orbit each other and periodically eclipse one another, leading to observable changes in brightness.