Roche lobe

The Roche lobe is a concept in astrophysics that describes the gravitational boundary around a star in a binary system, where the star can hold onto its material without it spilling over to its companion star. Imagine two stars close together; the Roche lobe defines the region around each star where gravity is strong enough to keep gas and dust from escaping to the other star. When a star's material crosses this boundary, it can be drawn toward its neighbor, leading to various phenomena, such as the formation of accretion disks or even explosive events like novae.