Variable stars

V838 Monocerotis

Variable stars

A star whose brightness changes is called a variable star.

Astronomers use a type of variable star called a Cepheid to measure distances in the Universe. There is a relationship between the length of time that it takes a Cepheid's brightness to change – its period – and its overall luminosity; Cepheids with longer periods are more luminous.

Astronomers compare the luminosity (calculated from the period) with how bright it appears in the sky to work out how far away the star is.

Image: V838 Monocerotis, a red variable star near our galaxy's edge (credit: Hubble Heritage Team, ESA, NASA)

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V838 Monocerotis


The brightness of stars can change.

About Variable stars

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