What would happen if a black hole crashed into a supernova?

Answer 1

This certainly would be a spectacular celestial event.

A lot would depend on the relative sizes and masses of the two objects - generally speaking a black hole, particularly the commonest type, the stellar mass black holes, are pinpricks in size by comparison to a star - let alone a supernova. It would also depend on the speed and "aim" of the collision - remember not only mass would be preserved but relative angular momentum. Gravitational interactions with a near miss would mean a mutual orbit around a common center of gravity with the heavier object occupying a near orbit with the lighter object, in this case a steady stream of matter from the supernova spiraling into the black hole. If the collision was more direct, all matter immediately in the path of the black hole's event horizon would fall in and be consumed by the black hole, and the remainder would eventually be subsumed into the black hole's accretion disk - remembering the preservation of angular momentum initially it would be very lop-sided and 'messy' but due to gravitational effects and the nature of matter in orbits it would eventually settle down and become planar. In either case, tidal effects would cause an apparent elongation (spaghettification) of the supernova in the direction of the gravitational pull of the black hole.

At the moment of collision likely significant amounts of matter (depending on the relative collision speed) would be flung out into space; almost all matter within the photon sphere of the black hole not traveling at relativistic speeds away from the black hole would already be occupying a path which would end up intersecting the black hole.

The black hole would also gain in size in direct proportion to the mass it consumed - but the pull it exerted would be no greater per unit mass than that of the supernova - in other words the expanding envelope of matter, particles, gas, or anything else from the supernova would no more get suddenly sucked back into the black hole by virtue of the fact that it is a black hole, than it would from the effects of the mass of the supernova; but having said that, the increase in mass that the presence of the black hole introduces would mean any outward expanding matter during the supernova's explosion would now be subject to a greater inhibiting pull on its expansion, or in other words would be expanding "up" a steeper gravitational gradient.

If the black hole was supermassive and significantly larger than the supernova there would be no question as to the winner of the direct collision - the supernova would be consumed. Tidal force would not spaghettify it significantly, an observer at the supernova might see the approach of a bright ring with a black center, and some redshifting in background stars owing to acceleration as it fell inwards; an observer some distance away, owing to relativistic effects (time dilation) might see the supernova appear to slow down and almost stop with a similar redshifting into invisibility as the light near the event horizon had to climb the black hole's gravitational gradient (per the Special Theory). For a rapidly spinning black hole, frame dragging effects would further distort the infalling matter.

Some other scenarios are conceivable. If the black hole were microscopic and traveling at relativistic speeds, its effect even with a direct hit on the center of the supernova might be barely noticeable and could potentially produce nothing more than a thin streamer of gas as it egressed the supernova somewhat like if a small bullet was to be shot through a large spherical wad of dust.

Answer 2

If a black hole were to crash into a supernova, it could engulf the remnants of the supernova, potentially leading to the formation of an even larger black hole. The collision may release a significant amount of gravitational energy and could result in the ejection of material at high speeds.