4 Jul 2019, 15:57 UTC
Like humans, the stars in our night sky are also typically born into large extended families. Star formation occurs in dense molecular clouds, in which many stars are typically born around the same time. If two stars are born close enough together to be gravitationally bound to each other, they form a binary system (or a triple system if there are three, etc.). These systems are so common that roughly half of the stars in our galaxy have companions, or siblings.