Black hole on fast spin cycle

A supermassive black hole halfway across the universe has been discovered spinning at almost half the speed of light, according to astronomers.

The speed of the spin, reported in the journal Nature, suggests the black hole’s galaxy merged wtih another around a billion years ago, says one of the paper’s authors Dr Mark Reynolds, of the University of Michigan.

This indicates the black hole has grown through cohesive rather than random episodes of mass accretion, bringing new insights into how galaxies evolved.

more…

>spinning at almost half the speed of light

Would play merry hell with your woollens.

Bubblecar said:

>spinning at almost half the speed of light

I don’t understand.

what don’t you understand?

How to spin something at half the speed of light.

Or even how to spin something at x km/h.

Surely it is revolutions per unit time, or it’s equivalent, not distance per unit time.

the eh is assumed to be travelling that fast…150 000 000m/s, just the speed at the equator of earth is about 278m/sec (or whatever it is )

of course the EH isn’t a “surface” so they measure the speed of stuff that is falling into the BH. the faster it orbits and falls in the higher the frequency of the x-rays emitted.

Michael V said:

How to spin something at half the speed of light.

Or even how to spin something at x km/h.

Surely it is revolutions per unit time, or it’s equivalent, not distance per unit time.

Yeah. The ABC article doesn’t make it clear, but the stuff moving at roughly half the speed of light is stuff in the black hole’s accretion disk.

From Universe Today

The spin rate of a supermassive black hole has been measured for the first time, and wow, is it fast. X-ray observations of RX J1131-1231 (RX J1131 for short) show it is whizzing around at almost half the speed of light. Through X-rays, the astronomers were able to peer at the rate of debris fall into the singularity, yielding the speed measurement.

“We estimate that the X-rays are coming from a region in the disk located only about three times the radius of the event horizon — the point of no return for infalling matter,” stated Jon Miller, an an associate professor of astronomy at the University of Michigan and a co-author on the paper. “The black hole must be spinning extremely rapidly to allow a disk to survive at such a small radius.”

Point is, it’s sloppy writing that is difficult to understand without making stuff up. One could assume that it’s the nominal EH that has that speed, but one shouldn’t have to make stuff up – ie make that assumption.

rpm is not km/h.

PM 2Ring said:

Michael V said:

How to spin something at half the speed of light.

Or even how to spin something at x km/h.

Surely it is revolutions per unit time, or it’s equivalent, not distance per unit time.

Yeah. The ABC article doesn’t make it clear, but the stuff moving at roughly half the speed of light is stuff in the black hole’s accretion disk.

From Universe Today

The spin rate of a supermassive black hole has been measured for the first time, and wow, is it fast. X-ray observations of RX J1131-1231 (RX J1131 for short) show it is whizzing around at almost half the speed of light. Through X-rays, the astronomers were able to peer at the rate of debris fall into the singularity, yielding the speed measurement.

“We estimate that the X-rays are coming from a region in the disk located only about three times the radius of the event horizon — the point of no return for infalling matter,” stated Jon Miller, an an associate professor of astronomy at the University of Michigan and a co-author on the paper. “The black hole must be spinning extremely rapidly to allow a disk to survive at such a small radius.”

Ah! Thanks PM.

Through X-rays, the astronomers were able to peer at the rate of debris fall into the singularity…

pretty darn good ‘scope.

;-)

Actually, even talking about the spin of a black hole in terms of RPM gets a bit hairy. So the usual approach is to simply state the black hole’s mass and its angular momentum.

According to GR, a spinning body adds a rotational component to the spacetime geometry in it vicinity. This effect is known as frame dragging or the Lense–Thirring effect. For a body like Earth, this effect is tiny, but for a rapidly spinning black hole the effect is huge.

See Kerr metric for the scary calculus involved in determining the angular velocity imparted to spacetime by a spinning body.