variable star
Definition
Noun: A variable star is a star whose observed brightness, or luminosity, as seen from Earth, changes over time. This variation can be regular or irregular and is caused by intrinsic changes in the star itself or by extrinsic factors like eclipses.
Usage
The term is used in astronomy to classify and study stars whose light output is not constant. - Astronomers monitor a variable star to understand its physical properties and life cycle. - The star Mira is a famous long-period variable star visible to the naked eye.
Advanced Usage
- Intrinsic variable star: A star whose brightness changes due to physical processes within the star, such as pulsation or eruptions. Example: Cepheid variables are crucial for measuring cosmic distances.
- Extrinsic variable star: A star whose observed brightness changes due to external factors, such as one star eclipsing another in a binary system. Example: Algol is an eclipsing binary variable star.
Variants and Related Words
- Variable (adj): Liable to change or vary. In astronomy, it specifically describes a star's changing brightness.
- Variability (n): The quality of being variable. In astronomy, it refers to the phenomenon of a star's changing brightness.
Synonyms
- Changing star (less common technical term)
- Flare star (a specific type of eruptive variable star)
Related Phrases
- Light curve: A graph showing the brightness of a variable star over time, which is the primary tool for its analysis.
- Period-Luminosity relation: A key property of certain types of intrinsic variable stars (like Cepheids) that links their pulsation period to their true brightness, making them "standard candles" for distance measurement.
Noun
-
a star that varies noticeably in brightness
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