A black hole is the ultimate triumph of gravity over matter. It is a region of space where the gravitational field is so strong that not even light can escape. Black holes a few times the mass of the Sun are probably created when massive stars explode at the end of their lives, while all galaxies are now thought to have black holes up to a thousand million times the mass of the Sun at their centres. Black holes can never be seen but reveal themselves through the release of energy from matter falling into them. The force of gravity starts to control and modify the fate of matter in the lowest-mass stars, which are only about 15 times the mass of Jupiter.
Gravity is the dominant force in shaping our universe on the largest scales.
It makes planets and stars spherical. It binds the planets to the Sun and the Sun and all the stars to our galaxy. It binds stars in clusters and holds clusters of galaxies together. It even controls the expansion of the universe. The answer is the conservation of energy and momentum and in this case, specifically angular momentum.