Stevenson 2-18: The Cosmic 'Puffball' Star That Could Swallow Saturn

Meet Stevenson 2-18, a star so colossal it’s earned the title of the universe’s "flabby giant." With a radius of 1.5 billion kilometers, this red supergiant would engulf Saturn if placed at the Sun’s position. Despite its eye-popping size, it packs only 15–20 times the Sun’s mass—making it a celestial "balloon" on the brink of a spectacular supernova explosion.