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LIGO detects most massive black hole merger to date

(www.caltech.edu)
360 points Eduard | 2 comments | 14 Jul 25 20:06 UTC | HN request time: 0.61s | source
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MattPalmer1086 ◴[14 Jul 25 20:52 UTC] No.44565128[source]▶
I wonder what would happen if one black hole shot through another one at high relativistic velocity, instead of spiralling towards one another.
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fsmv ◴[14 Jul 25 20:53 UTC] No.44565138[source]▶
They would merge and produce a black hole with the sum of their momentums

Because nothing can ever leave the event horizon black holes are essentially perfectly sticky.

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1. MattPalmer1086 ◴[15 Jul 25 21:06 UTC] No.44575822[source]▶
What if the collision was only a grazing one, not head on?

Would they still fully merge, or might you get a mass exchange between them? Or even a smaller black hole spun off?

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2. MattPalmer1086 ◴[15 Jul 25 21:45 UTC] No.44576143[source]▶
To answer my own question, some lay research shows it seems it is technically possible for them not to merge if only a tiny portion of their apparent event horizons merge and for only very briefly.

But this is because of a distinction between the Apparent Horizon [1] (which is coordinate-dependent) and the true global event horizon. So they appear to briefly merge but no true global event horizon forms to encompass both. I think!

[1] https://physics.stackexchange.com/questions/38721/what-is-th...