variable star

American  

noun

Astronomy.

1. a star that varies markedly in brightness from time to time.

---

variable star British  

noun

1. any star that varies considerably in brightness, either irregularly or in regular periods. Intrinsic variables, in which the variation is a result of internal changes, include novae, supernovae, and pulsating stars See also eclipsing binary

---

variable star Scientific  

1. A star whose actual or observed brightness varies periodically. These changes can occur with varying degrees of regularity and intensity, over times ranging from a fraction of a second to many years. Intrinsic variation occurs because of changes of the star itself, often due to internal vibration or eruptions, or to influx of nearby material. Cepheids and novae are examples of intrinsically variable stars. Extrinsic variation in a star's observed brightness that does not reflect physical changes in the star also occur, as when a darker star periodically eclipses a brighter star in an eclipsing binary system, or with the rotation of a star.

---

Etymology

Origin of variable star

First recorded in 1780–90

Example Sentences

The Christmas Tree Star Cluster Near the center of NGC 2264 is S Monocerotis, a bright variable star whose brightness changes over time.

From Science Daily • Dec. 25, 2025

The triple-star system is made up of the variable star HP Tau, HP Tau G2, and HP Tau G3.

From Science Daily • May 15, 2024

In 1994, using the Hubble Space Telescope, astronomers were able to make out an individual cepheid variable star in the galaxy M100 and measure its distance to be 56 million light-years.

From Textbooks • Oct. 13, 2016

For 100 years astronomers have paid particular attention to a class of variable star known as the Cepheids.

From Economist • Apr. 7, 2011

Beta Cephei is a variable star in the Constellation Cepheus.

From Astounding Stories of Super-Science July 1930 by Bates, Harry