Which types of variable stars are commonly found in globular clusters?

Globular clusters are known to contain a variety of variable stars, with approximately 2,000 identified across examined clusters. The most prevalent type is the RR Lyrae variable, which accounts for roughly 90 percent of the variable stars found in these systems.12

Other types of variable stars commonly observed in globular clusters include:

• Population II Cepheids: These are distinct from the classic Population I Cepheids found in the spiral arms of the Milky Way.3
• RV Tauri stars: A type of red semiregular variable that exhibits complex light and spectral changes.23
• U Geminorum stars: A class of cataclysmic variables.2
• Mira stars: Long-period variables that are typically cool red giants.23
• Eclipsing binaries: Systems where one star periodically passes in front of another from our perspective.2
• Novas: Explosive stellar events.2

RR Lyrae stars are particularly significant in astronomy because they serve as reliable distance indicators. When present in a globular cluster, they are located in a specific region of the colour-magnitude diagram known as the RR Lyrae gap, situated near the blue end of the horizontal branch.415