What happens if a huge star collides with a small black hole?


We recently received the following question from one of our subscribers:

The result of a collision of any star with a black hole depends on the nature of this collision, collisions of such large-scale objects as stars extremely rarely occur head-on, usually objects pass at some distance from each other, twisting around a common center of mass.

Under certain conditions, they can form a stable system, but often bodies scatter again in different directions. If we assume that the black hole and the star have formed a stable system, then if the hole is located at a great distance from the star, then it will not absorb stellar matter and the star and the black hole will revolve around a common center of mass.

If the hole is close to or below the surface of the star, then tidal forces will begin to tear apart the star and drag the star’s matter into the black hole. In this case, the rate of absorption of matter is limited by the size of the black hole, therefore, when a large star and a small black hole collide, a large percentage of the matter will be accelerated by rotation around the hole and thrown into space.

Over time, the hole will upset the balance between the force of gravity of the star and the force of pressure in its interior, which will lead to the explosion of the star, in which only part of the matter will be absorbed by the black hole. The scale of the explosion depends on the parameters of the star and the black hole; a simulation of the absorption of a small star by a small black hole is shown below.

The larger the black hole, the more star material it is able to absorb, but only supermassive black holes with masses of hundreds of millions and billions of solar masses can swallow the stars almost completely.