• Question: what would happen if 2 black holes collided

    Asked by rocs532noes77 on 16 Mar 2026. This question was also asked by raga532warm99.
    • Photo: Jade Gray

      Jade Gray answered on 16 Mar 2026:

      If you have two black holes coming together, they start to orbit each other first, spinning around each other getting closer and closer together. Eventually when they crash together they combine and create an even larger black hole. We call this type of event a black hole merger. When they merge, they send ripples through space called gravitational waves.

    • Photo: Emily Walls

      Emily Walls answered on 17 Mar 2026:

      Similar to what Jade said, they orbit eachother until they come together to form a bigger black hole and when this happens, we can measure gravitational waves on Earth with instruments like LIGO 🙂

    • Photo: Conall Kavanagh

      Conall Kavanagh answered on 24 Mar 2026:

      I work on modelling black hole collisions when they have discs of gas around them using computer simulations. There is loads of gas all throughout space and, because black holes are so massive, they pull in a lot of this gas to form (‘accretion’) discs. These get unbelievably hot and so then glow very brightly, sometimes outshining whole galaxies. This is what allows us to ‘see’ the black holes but also should help them to merge. When two supermassive black holes are spiralling together in the centre of a galaxy which has merged with another, there is loads of gas around and this forms into a disc around both black holes. The disc and the holes interact in lots of interesting ways and computer simulations show the disc helps to push the black holes together. Eventually, when they get close enough, gravitational waves cause them to rapidly fall together. The collision of two supermassive black holes is probably the most energetic single event in the Universe that we are currently aware of. When they collide only a single larger black hole remains, but so much energy is released (and energy and mass are equivalent) that it weighs quite a lot less than if you just added the two collided black hole masses together!

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