A pulsating star is a type of star that experiences periodic changes in brightness due to variations in its size and temperature. These changes occur as the star expands and contracts, often driven by internal processes such as nuclear fusion. Common examples of pulsating stars include Cepheid variables and RR Lyrae stars, which are important for measuring cosmic distances. The pulsation periods of these stars can range from a few hours to several days. Astronomers study pulsating stars to gain insights into stellar evolution and the structure of the universe. Their predictable brightness variations make them valuable tools for understanding the scale of the cosmos.