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.
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Henrietta Swan Leavitt discovered the period-luminosity relationship of Cepheid variables in 1908.
Cepheids have pulsation periods ranging from a few days to several weeks.
The luminosity of a Cepheid is directly proportional to its pulsation period; longer periods mean brighter stars.
Cepheid variables serve as 'standard candles' for determining distances within our galaxy and nearby galaxies.
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.