APOD: Binary Black Hole in 3C 75 (2010 Mar 14)

[APOD Robot]

Binary Black Hole in 3C 75

Explanation: What's happening in the middle of this massive galaxy? There, two bright sources at the center of this composite x-ray (blue)/radio (pink) image are thought to be co-orbiting supermassive black holes powering the giant radio source 3C 75. Surrounded by multimillion degree x-ray emitting gas, and blasting out jets of relativistic particles the supermassive black holes are separated by 25,000 light-years. At the cores of two merging galaxies in the Abell 400 galaxy cluster they are some 300 million light-years away. Astronomers conclude that these two supermassive black holes are bound together by gravity in a binary system in part because the jets' consistent swept back appearance is most likely due to their common motion as they speed through the hot cluster gas at 1200 kilometers per second. Such spectacular cosmic mergers are thought to be common in crowded galaxy cluster environments in the distant universe. In their final stages the mergers are expected to be intense sources of gravitational waves.

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[madtom1999]

So we have two black holes whose event horizons are, according to relativity, not moving as far as we can see, circling each other.
Sweet!

[neufer]

• 

This image from the Digitized Sky Survey (DSS)/Palomar 48-inch Schmidt telescope shows NGC 1128 in visible light. The peculiar dumbbell structure of this galaxy is thought to be due to two large galaxies that are in the process of merging. Such mergers are common in the relatively congested environment of galaxy clusters. An alternative hypothesis is that the apparent structure is the result of a coincidence in time when the two galaxies are passing one another, like ships in the cosmic sea. (Credit: Pal.Obs. DSS)

[Chris Peterson]

So we have two black holes whose event horizons are, according to relativity, not moving as far as we can see, circling each other.

What exactly do you mean by this? The event horizons move with the black holes.

[neufer]

So we have two black holes whose event horizons are, according to relativity, not moving as far as we can see, circling each other.

What exactly do you mean by this? The event horizons move with the black holes.

• _____ King Lear Act IV, scene I
  
  Old Man: 'Tis poor mad Tom.
  
  EDGAR: [Aside] And worse I may be yet: the worst is not
  _____ So long as we can say 'This is the worst.'

[biddie67]

The sense of what could be the possible ripple effect on our little world if those two black holes collide and explode, black hole style, is fearsome to speculate.

[Chris Peterson]

The sense of what could be the possible ripple effect on our little world if those two black holes collide and explode, black hole style, is fearsome to speculate.

I wouldn't worry. Gravity waves are not destructive. Black holes like these have collided many times in the history of the Universe, without effect outside their immediate environs. It is only now that we have the technology to possibly detect the waves created by such collisions- nothing but the most exquisitely sensitive instruments can do so.

[neufer]

The sense of what could be the possible ripple effect on our little world if those two black holes collide and explode, black hole style, is fearsome to speculate.

I wouldn't worry. Gravity waves are not destructive. Black holes like these have collided many times in the history of the Universe, without effect outside their immediate environs. It is only now that we have the technology to possibly detect the waves created by such collisions- nothing but the most exquisitely sensitive instruments can do so.

<<Based on current models of astronomical events, and the predictions of the general theory of relativity, gravitational waves that originate tens of millions of light years from Earth are expected to distort the Laser Interferometer Gravitational-Wave Observatory (LIGO) 4 kilometer mirror spacing by about 10⁻¹⁸ m, less than one-thousandth the "diameter" of a proton. Equivalently, this is a relative change in distance of approximately one part in 10²¹. A typical event which might cause a detection event would be the late stage inspiral and merger of two 10 solar mass black holes, not necessarily located in the Milky Way galaxy, which is expected to result in a very specific sequence of signals often summarized by the slogan chirp, burst, quasi-normal mode ringing, exponential decay.

As of November 2005, sensitivity had reached the primary design specification of a detectable strain of one part in 10²¹ over a 100 Hz bandwidth. The baseline inspiral of two roughly solar-mass neutron stars is typically expected to be observable if it occurs within about 8,000,000 parsecs (26,000,000 ly), or the vicinity of our Local Group of galaxies, averaged over all directions and polarizations. In 2004, it was reported that theorists were estimating the chances of unambiguous direct detection by 2010 at one in six.

In February 2007, GRB 070201, a short gamma-ray burst, arrived at Earth from the direction of the Andromeda Galaxy, a nearby galaxy. The prevailing explanation of most short gamma-ray bursts is the merger of a neutron star with either a neutron star or black hole. LIGO reported a non-detection for GRB 070201, ruling out a merger at the distance of Andromeda with high confidence. Such a constraint is predicated on LIGO eventually demonstrating a direct detection of gravitational waves.>>

[ajbock]

Art, I'm not worried a bit either. -ajb

[madtom1999]

Cheers neufer - abuse is the first sign of a lost argument - quoting Shakespeare must come a close second. A point for getting the quote.

Chris P - perhaps but the black holes must, by their own definition appear stationary to us. The event horizon is, to all intents and purposes, an immutable, immoveable thing. Recently it was shown that 'gravity' moves at the speed of light. So event horizons cant go anywhere - we can have no knowledge of the other side whatsoever - including momentum, angular or otherwise. Frame dragging doesn't seem to work here either - the frames disappear into infinity as they approach the event horizon.

As for LIGO - I'm wondering if this isn't ultimately a Michelson-Morley moment - its been 'next year' or so for the last odd 40 years!

[Chris Peterson]

Chris P - perhaps but the black holes must, by their own definition appear stationary to us. The event horizon is, to all intents and purposes, an immutable, immoveable thing.

I'm afraid I still don't understand your point. Black holes are simple objects. We can see them move like any other object. If one were in orbit around the Sun, we'd observe it moving just like the planets. We do see actual motion in the case of binary black holes. Black holes do not appear stationary with respect to other objects.

The event horizon itself is just a surface. It has no features that would allow us to see it move with respect to the center of the black hole. But that doesn't necessarily mean it isn't moving. Black holes have spin, and that may mean that the "surface" defined by the event horizon is spinning as well.

[neufer]

Chris P - perhaps but the black holes must, by their own definition appear stationary to us. The event horizon is, to all intents and purposes, an immutable, immoveable thing.

I'm afraid I still don't understand your point. Black holes are simple objects. We can see them move like any other object. If one were in orbit around the Sun, we'd observe it moving just like the planets. We do see actual motion in the case of binary black holes. Black holes do not appear stationary with respect to other objects. The event horizon itself is just a surface. It has no features that would allow us to see it move with respect to the center of the black hole. But that doesn't necessarily mean it isn't moving. Black holes have spin, and that may mean that the "surface" defined by the event horizon is spinning as well.

Hmmmmmm.....this is a conundrum.

We have always been taught that from our frame of reference the event horizon is a "frozen" surface above which falling objects hang in suspended animation while barely radiating at all. And yet we know that both gravitational & electromagnetic fields are spinning rapidly outside the black hole ejecting "johnny come late-lies" out from the poles.

So can one really say that <<the "surface" defined by the event horizon is spinning as well?>>

[Chris Peterson]

Hmmmmmm.....this is a conundrum.

We have always been taught that from our frame of reference the event horizon is a "frozen" surface above which falling objects hang in suspended animation while barely radiating at all. And yet we know that both gravitational & electromagnetic fields are spinning rapidly outside the black hole ejecting "johnny come late-lies" out from the poles.

So can one really say that <<the "surface" defined by the event horizon is spinning as well?>>

I don't see the conundrum. I agree with your description of the behavior of an event horizon as seen from a distant frame of reference- except for your use of the term "frozen". Where does that come from? Also, I think it's fair to say we know that EM fields are spinning around black holes, but we depend on theory for our assumption that a gravitational field is spinning. I don't think that's been established experimentally or observationally (although I don't have much doubt it's true).

My point was really that the surface might turn out to be spinning in some physical sense, or not. I don't see that this necessarily has any obvious ramifications for the observed behavior of material near a black hole.

[neufer]

I agree with your description of the behavior of an event horizon as seen from a distant frame of reference- except for your use of the term "frozen". Where does that come from?

Time comes to a stop; ergo: frozen as in no internal (as well as external) motion.

It is a black hole because all thermal radiation has effectively stopped.

[Markus Schwarz]

Time comes to a stop; ergo: frozen as in no internal (as well as external) motion.

The first part of your statement is only valid for an observer far away from the Black Hole's horizon (as you emphasized yourself earlier). An observer falling freely could very well pass through the horizon without feeling anything. Two different observers perceive time to run at different rates. Here is an analogy: imagine standing on a railway track. Near you, the rails have a constant separation and are parallel. Yet at the distant horizon they seem to cross, although every local measurement will tell you that they have a constant separation. The important difference between time and the railway track is that the later effect is an optical illusion, whereas the former effects have been measured near Earth. The „slow-down of time“ is taken into account by the GPS system, and the frame-dragging effect has been observed by the Gravity Probe B experiment. Hence, all these „weird event horizon“ effects are present on Earth, but are tiny because gravity is weak, here.

It is a black hole because all thermal radiation has effectively stopped.

What do you mean by “effectively”? Using just classical physics, one finds that a Black Hole does not emit radiation. However, semi-classical calculations show that they do emit thermal radiation (Hawking radiation).

[andre]

Great picture but don't know how it be somthing are wrong two black holes so near may the human astrom can watch in mio's of years what goes on and what will be if two black holes fight of her own existance.