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Scientists confirm that the first black hole ever imaged is actually spinning (www.engadget.com)
submitted 2 years ago by [M, B] to c/technology@lemmy.world
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Scientists confirm that the first black hole ever imaged is actually spinning::The first black hole humanity has ever imaged has also provided us with what researchers are calling "unequivocal evidence" that black holes spin.

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[–] 5 points 2 years ago (5 children)

Does the black hole spin? Or does the stuff outside the black hole spin? 🤔

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  • [–] 20 points 2 years ago (1 child)

    The black hole and the stuff outside it constitute a single system, and within that system, angular momentum is conserved. So as objects cross the event horizon, their angular momentum is transferred to the black hole.

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  • [–] 1 point 2 years ago (2 children)

    Well.... does it? If all the stuff falls in and only the volume remains, who could say that it's spinning? How could you detect it?

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  • [–] 12 points 2 years ago* (last edited 2 years ago) (2 children)

    For one thing, the size and shape of the event horizon change depending on the black hole’s spin.

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  • [–] 1 point 2 years ago (1 child)

    I see. Thank you. So, you can use light to infer the mass, and then the volume information to infer the spin? Easy enough.

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  • [–] 3 points 2 years ago* (last edited 2 years ago)

    That would be a general method, if we were close enough to observe the shape of the event horizon (which we aren’t).

    The article is describing another way, which only works in this case because the black hole is precessing so extremely that the changing axis of rotation is frame-dragging the polar jets along with it.

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  • [–] 1 point 2 years ago (1 child)

    I thought nothing actually crossed the event horizon and was essentially frozen approaching a complete stop in time in a kind of 2f representation of 3d reality until it slowly leaked out trillions of years later as hawking radiation?

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  • [–] 0 points 2 years ago

    From an outsider's perspective, you would see an object approach and then freeze. It would red-shift dimmer until it disappeared. From an in-falling perspective, I don't think you'd notice anything at all.

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  • [–] 6 points 2 years ago

    Isn’t most everything spinning? Seems like having zero angular momentum would be rare and remarkable. I’m not even sure how exactly to define zero momentum in terms of reference frames.

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  • [–] 2 points 2 years ago (1 child)

    If you're asking that then you first need to ask what the distinction between the two is. and further does it even make sense for one to spin and not the other

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