Final answer:
A pulsating star is a type of star whose luminosity changes as it periodically expands and contracts. An example of a pulsating star is a Cepheid variable star, which is used as a distance indicator in astronomy.
Step-by-step explanation:
A pulsating star is a type of star whose luminosity changes as it regularly expands and contracts. These changes in luminosity cause the star to appear to pulsate or vary in brightness over time. Pulsating stars can have periods ranging from a few hours to several weeks.
An example of a pulsating star is a Cepheid variable star. Cepheids are stars that pulsate in a regular and predictable manner, allowing astronomers to use them as distance indicators in the universe. By studying the period of a Cepheid's pulsations, astronomers can determine its intrinsic brightness and calculate its distance from Earth.