Cepheid

1. Any of a class of variable stars whose luminosity fluctuates with an extremely regular period. There is a strong correlation between the absolute magnitude of a Cepheid's luminosity and its period. By comparing the apparent magnitude of a Cepheid to the absolute magnitude corresponding to its period, it is possible to determine fairly accurately how distant the Cepheid is from Earth.

2. Also called Cepheid variable

Example Sentences

She was particularly interested in Cepheid variables, which are stars whose brightness pulses regularly, so they get brighter and dimmer with a particular period.

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Once you measure a Cepheid’s period, you can calculate its distance from how bright it appears using the inverse square law.

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Hubble worked hard, taking images of spiral nebulae every clear night and looking for the telltale variations of Cepheid variables.

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He calculated M31’s distance as a prodigious 900,000 light years away, though he underestimated its true distance – about 2.5 million light years – by not realizing there were two different types of Cepheid variables.

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But some astronomers suggested that, moving outward along the "second rung," the cosmic distance ladder might get shaky if the Cepheid measurements become less accurate with distance.

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