Glossary term: Effective Temperature

Description: The effective temperature of a star is the temperature of a theoretical perfect emitter (a "blackbody") that has the same surface area and the same total light output as the star.

Stars have different layers with different temperatures, several of which contribute to what we eventually receive as starlight. Often astronomers find it useful to represent a star by a much simpler model, namely an idealized light-emitter called a "blackbody". A blackbody's total energy output is completely determined by specifying two parameters: its temperature and its surface area. The star's effective temperature is the temperature of a blackbody which has the same surface area and same total energy output as the star.

The effective temperature is one useful way to average the contributions to the star's light output from different parts of its outer layers and typically has a value very similar to the temperature of the star's photosphere – the surface layer where most of the star's light originates.

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Term and definition status: This term and its definition have been approved by a research astronomer and a teacher

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