stellar astronomy

Globular clusters are the oldest and densest stellar systems in the universe — spherical swarms of hundreds of thousands of stars bound together for billions of years. Here's how they form, what they reveal about galactic history, and why they remain one of astronomy's most productive laboratories.

Roughly 44% of Sun-like stars have a companion, and the share climbs past 80% for the most massive stars. Binary stars let astronomers weigh stars, produce Type Ia supernovae and millisecond pulsars, and generate the gravitational waves LIGO detects.