The gravitational discipline of a rotating black gap is highly effective and unusual. It’s so highly effective that it warps house and time again upon itself, and it’s so unusual that even easy ideas resembling movement and rotation are turned on their heads. Understanding how these ideas play out is difficult, however they assist astronomers perceive how black holes generate such large vitality. Take, for instance, the idea of body dragging.
Black holes kind when matter collapses to be so dense that spacetime encloses it inside an occasion horizon. This implies black holes aren’t bodily objects in the best way they’re used to. They aren’t fabricated from matter, however are moderately a gravitational imprint of the place matter was. The identical is true for the gravitational collapse of rotating matter. After we speak about a rotating black gap, this doesn’t imply the occasion horizon is spinning like a prime, it signifies that spacetime close to the black gap is twisted right into a gravitational echo of the as soon as rotating matter. Which is the place issues get bizarre.
Suppose you have been to drop a ball right into a black gap. Not orbiting or rotating, only a easy drop straight down. Quite than falling in a straight line towards the black gap, the trail of the ball will shift towards an orbital path because it falls, transferring across the black gap ever quicker because it will get nearer. This impact is called body dragging. A part of the “rotation” of the black gap is transferred to the ball, though the ball is in free fall. The nearer the ball is to the black gap, the better the impact.
A latest paper on the arXiv reveals how this impact can switch vitality from a black gap’s magnetic discipline to close by matter. Black holes are sometimes surrounded by an accretion disk of ionized gasoline and dirt. As the fabric of the disk orbits the black gap, it might generate a strong magnetic discipline, which may superheat the fabric. Whereas a lot of the energy generated by this magnetic discipline is attributable to the orbital movement, body dragging can add an additional kick.
Basically, a black gap’s magnetic discipline is generated by the majority movement of the accretion disk. However thanks to border dragging, the inside portion of the disk strikes a bit quicker than it ought to, whereas the outer portion strikes a bit slower. This relative movement between them signifies that ionized matter strikes relative to the magnetic discipline, making a type of dynamo impact. Thanks to border dragging, the black gap creates extra electromagnetic vitality than you’d anticipate. Whereas this impact is small for stellar mass black holes, it’s massive sufficient for supermassive black holes that we would see the impact in quasars via gaps of their energy spectrum.
Reference: Okamoto, Isao, Toshio Uchida, and Yoogeun Music. “Electromagnetic Power Extraction in Kerr Black Holes via Body-Dragging Magnetospheres.” arXiv preprint arXiv:2401.12684 (2024).
