Cepheid

Definition

Cepheids are a type of variable star that exhibit regular changes in brightness with well-defined periods. They are crucial for measuring cosmic distances due to their period-luminosity relationship.

5 Must Know Facts For Your Next Test

1. Henrietta Swan Leavitt discovered the period-luminosity relationship of Cepheid variables in 1908.
2. Cepheids have pulsation periods ranging from a few days to several weeks.
3. The luminosity of a Cepheid is directly proportional to its pulsation period; longer periods mean brighter stars.
4. Cepheid variables serve as 'standard candles' for determining distances within our galaxy and nearby galaxies.
5. There are two main types of Cepheids: Classical Cepheids, found in the disk of the Milky Way, and Type II Cepheids, generally older and found in globular clusters.

Review Questions

• What fundamental property of Cepheids makes them useful for measuring cosmic distances?
• Who discovered the period-luminosity relationship that underpins the use of Cepheids as standard candles?
• Differentiate between Classical and Type II Cepheids.

Related terms

Variable Star: A star whose brightness as seen from Earth fluctuates over time.

Standard Candle: An astronomical object with a known luminosity used to measure distances in space.

Period-Luminosity Relationship: The correlation between the luminosity and pulsation period of certain variable stars like Cepheids.