UY Scuti Reigns as the Universe’s Biggest Known Star, but Its Crown May Be at Risk

UY Scuti, a red hypergiant about 1,700 times the Sun’s radius, is the universe’s largest known star. Nearly 5 billion suns could fit inside its volume, but rivals like NML Cygni and Westerlund 1-26 challenge its claim to the crown. Astronomers stress that size estimates carry large uncertainties, leaving the title of biggest star still contested.