Wikipedia:Reference desk/Archives/Science/2019 December 24

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December 24

Black hole observation

Some sources state that scientists can't directly observe black holes with telescopes. This doesn't seem to be entirely true. Wouldn't a black hole reveal itself as an unnaturally black region of space devoid of all stars and light, with gravitational lensing around it - and thus being technically observable through telescopes at least in visible spectrum? Several animated simulations at black hole show it's indeed observable optically. 212.180.235.46 (talk) 15:37, 24 December 2019 (UTC)

I think we're inevitably just going to be quibbling over the weakly-defined term, "direct observation." It ultimately isn't a very important detail whether we observe "directly" or "indirectly." All that matters is whether the evidence is convincing. Nimur (talk) 16:39, 24 December 2019 (UTC)

See also Void (astronomy). --Cookatoo.ergo.ZooM (talk) 16:59, 24 December 2019 (UTC)

Scientists and others cannot observe anything going into an event horizon even in theory. (unless they are falling in themselves) In some sense from our point of view a black hole has not yet formed. But the infalling matter is redshifted to invisibility would appear black. Currently there are no optical telescopes that could see the black region, as black holes are too tiny, casting a very small angle on the sky. They can however observe the effects on nearby matter, eg in an active galactic nucleus, or the stars orbiting Sgr A*. I assume you have read Event Horizon Telescope, which is a synthesized radio telescope. Graeme Bartlett (talk) 21:31, 24 December 2019 (UTC)

Yes, you are right. Moreover one black hole was already observed in this manner. Ruslik_Zero 19:06, 25 December 2019 (UTC)