Wikipedia:Reference desk/Archives/Science/2025 August 4
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August 4
editBlack hole shape
editCould a black hole be a long filament, many light years long, instead of a round ball? Could the black hole filament curve around and connect with itself to form a black hole donut?Rich (talk) 11:16, 4 August 2025 (UTC)
- No, but you may be interested in cosmic strings. --Wrongfilter (talk) 11:47, 4 August 2025 (UTC)
- You may consider a ring shaped chain of black holes orbiting in a circle. Could these fuse into a donut? THis question was asked in this paper: Cohen, Michael I.; Kaplan, Jeffrey D.; Scheel, Mark A. (18 January 2012). "Toroidal horizons in binary black hole inspirals". Physical Review D. 85 (2): 024031. doi:10.1103/PhysRevD.85.024031. and the answer appears to be no. But this paper claims temporarily yes: https://doi.org/10.1103/PhysRevD.94.064009 Graeme Bartlett (talk) 12:29, 4 August 2025 (UTC)
- So the answer appears to be that either shape (of the event horizon) is not stable and will contract to form an oblate spheroid. ‑‑Lambiam 14:14, 4 August 2025 (UTC)
- Like a Rugby ball, only heaver. ←Baseball Bugs What's up, Doc? carrots→ 16:26, 5 August 2025 (UTC)
- Black holes are not necessarily large, and rugby balls are prolate spheroids. If one managed to reach black-hole density, it too would become oblate. ‑‑Lambiam 17:35, 5 August 2025 (UTC)
- Like a Rugby ball, only heaver. ←Baseball Bugs What's up, Doc? carrots→ 16:26, 5 August 2025 (UTC)
- So the answer appears to be that either shape (of the event horizon) is not stable and will contract to form an oblate spheroid. ‑‑Lambiam 14:14, 4 August 2025 (UTC)
- If by "black hole" you mean its singularity, all rotating black holes have not a point singularity, but instead a ring singularity or ringularity which rotates, which you could consider a "black hole donut." (However, the black hole most likely wouldn't look like a donut.) OutsideNormality (talk) 03:48, 6 August 2025 (UTC)