The constellation Orion rolls across the southern sky on winter evenings. The hunter's brightest stars are Betelgeuse, which represents his shoulder, and Rigel, at his foot. Three moderately bright stars form his belt. All five of these stars are far larger and heavier than the Sun, and are likely to end their lives with titanic explosions. Alnilam, at the center of the belt, is the most impressive of them all. Orion's Sword, which includes the star-making Orion Nebula, is below the belt.