• Question: how big can black holes get

    Asked by reds532jazz9 to Vicky F, stephaniebuttigieg, sraimundo, ryanbegley, jadegray, ievajankute, conallkavanagh on 17 Oct 2025.
    • Photo: Vicky Fawcett

      Vicky Fawcett answered on 17 Oct 2025:

      The largest black hole we have discovered is TON 618, which is ~60 billion times more massive than the Sun!
      However, there is no reason why you can’t get bigger black holes… the more stars and black holes a black hole eats, the bigger it gets!

    • Photo: Conall Kavanagh

      Conall Kavanagh answered on 17 Oct 2025:

      Black holes can grow to be incredibly massive, the one at the centre of our galaxy (Sagitarius A*) is around 4 million times the mass of the sun, and as Vicky said, some can be over 10,000 times bigger than that. Material feeds onto black holes (allowing them to grow) through discs of gas, and this is what makes them visible to us (look at a photo of Sagitarius A* and what you are seeing is the accretion disc around it). There is a point where the black hole is so large that the disc of gas cannot exist around it, and so it would not be visible to us. For the most extreme scenario of a black hole spinning very quickly, this limit is thought to be about 270 billion times the mass of the sun. Black holes may be able to grow far more massive than this, and when they collide their masses roughly add, but they would not be visible to us! For context, these masses are comparable to those of an average galaxy, which is crazy to think about.

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