We aren’t sure exactly how, or how much of, the original star’s rotation is passed to the black hole, but we know that the black hole likely will form with angular momentum. Like a figure skater that pulls her arms in and spins faster, the star’s rate of rotation increases as the star itself gets smaller in radius due to conservation of angular momentum. We think all stars spin, and thus so did the sun that collapsed into a remnant black hole. If a star begins its life with more than some critical mass (usually estimated at about 10 to 20 times the Sun’s mass), it will ultimately end up as a black hole. This concept can be difficult to visualize because a black hole is not a solid body, but it helps if you start by imagining a black hole as the end product of a star’s evolution.

We refer to this property as “spin” or, more formally, its “angular momentum” about its axis of rotation. A: Like most objects in the universe (planets, stars, asteroids, and other compact objects), black holes rotate.

All star spins