BAM! Astroboffins now have a second way of picking up black holes' collision super kicks Gravitational waves released from black hole “super kicks” may soon be detectable, according to new research published in Physical Review Letters. Einstein realised that gravitational waves were a product of his theory of General Relativity, which found that spacetime behaved like a fabric. When objects with mass – such as …
"...remnants of the black holes are flung out of the galaxy and cast into the emptiness of space."
What, according to theory, becomes of these remnants? One would suppose they are now insufficiently massive to continue as a black hole. Does the matter in that remnant "become visible" again or "return to normal" for lack of more precise terms OR does the remnant evaporate in much the same way as we have been reassured would happen to quantum or nano-scale holes created from LHC collisions?
Regardless of the answer, I am delighted at the pace of recent scientific expansion. If this keeps up, we might actually find a reason to stop killing each other long enough to get off this little blue ball.
If I've got this right, light can't escape a black hole because it also behaves like a particle and is sucked in by the gravity, so speed isn't really a factor inaroun; it doesn't matter how fast the black hole is moving, and the light always moves at the speed of light anyway.
What I'm trying to wrap my mind around is the bit about "detecting a black hole kick would mean a direct observation that gravitational waves are carrying not just energy, but linear momentum as well."
How can there be "remnants" of black holes unless they are broken up somehow? If they are, doesn't that violate the whole "what goes in never comes out" (except as Hawking radiation) dicta of black holes?
Is there an actual astroboffin in the house who can explain this? I imagine the article has been translated from science-speak to journalist-speak a few times along the way and lost some of its meaning, rather than black holes actually having remnants flung about.
IANAA (I am not an astroboffin), but here's my best shot at an explanation:
A black hole is a super-dense collection of matter, emitting such a strong gravitational force that light is not energetic enough to escape. Presumably, the collective gravitational force of the black hole could be overcome by the introduction of sufficient energy from another source, say the kinetic energy from a collision with another black hole, causing all that matter to fly apart. That's as specific as I'm willing to get with my uneducated speculation.
Regrettably us commentards have to translate journalist into science. 'Dog particle' -> 'Higgs boson', and 'remnants of a black hole' -> 'remnants of a star most of which collapsed into a black hole'.
Water at the bottom of a waterfall is hotter than at the top because the water collected energy as it fell. Likewise when the core of a star collapses it gets hotter and the heat causes the outer layers to expand. When the core collapses all the way to a black hole it blasts most of the outer layers away. Some outer layers stay in orbit around the black hole, and more matter gets pulled back forming an accretion disk.
An accretion disk is like the rings of Saturn, where the inner rings go round the planet faster than the outer rings. Accretion disks are much denser and friction between matter in adjacent orbits creates enough heat to glow X-ray coloured. When two black holes are close together each can have a small accretion disk where the gravity from one hole is far bigger than the other. The pair of holes have a large accretion disk that starts at a radius that is large compared to the distance between the two holes. Closer in, matter is in a chaotic orbit that switches between going around either black hole or going around the pair.
Two black holes spinning around each other have several solar masses more energy than the same to merged together. All that energy is converted into gravitational waves in a few seconds. The waves are so big we can just about detect them thousands of light years away. A thousand kilometres away from a merge, the waves are insanely powerful and do interesting things to accretion disks.
Just to add some details to Flocke Kroes's explanation...
When a body is compressed to <= the Shwarzchild radius for the mass of that body it will undergo a runaway gravitational collapse and the current thinking, according to the Quantum Mechanics Standard Model, is that this collapse will continue until it reaches the size of the Planck Length, which is about 1.61 x 10-35 metres. For comparison, the radius of a Proton is about 0.86 x 10-15 metres, so the singularity at the center of a Black Hole is of the order of 1020 times smaller than a Proton.
However, whilst the size of the singularity within a BH is not dependant upon its mass - all singularities collapse to the PL, regardless of mass - there's also the 'Event Horizon', which is in proportion to the mass*; the size of the EH for a body of the same mass as the Earth is about 8.8 mm, and for Sol, about 2.95km.
Now, whilst most people are aware that the EH marks the distance from the singularity where the Escape Velocity is equal to 'c' - the Speed of Light - it also marks the distance from the singularity where Gravitational Time Dilation means that the local rate of time reaches zero, so not only is there the problem of something that's trying to 'leave' a BH being unable to go faster than 'c', it's also got to try to do something (change its state) in a local time period of zero. This would seem to mean that if the state of a body that crosses an EH is to change then it must enter a super-position of states so that, in much the same way as Schrodinger's cat is both simultaneously dead and alive, the body is both simultaneously changed and unchanged.
So forget simplistic descriptions of what BHs are doing; everything that's observable occurs outside an EH; everything, if anything, that goes on within an EH is beyond physics, as far as we currently understand it, except in the most abstract forms.
*<pureSpeculationAlert>The fact that the size of the Event Horizon appears to be dependant upon the mass of the singularity, which is beyond the EH, is interesting; if nothing can escape a BH/EH then why is there still gravity? It would seem that either gravity can pass the EH, even though it's confined by 'c', or perhaps, due to the gravitational time dilation effects, we're actually observing what is essentially a bit of 'frozen' time; the 'real' mass no longer effectively exists in our universe but the historical effects of it do. Who knows? I certainly don't, but when it comes down to it, as far as BHs are concerned, all you've really got to play with is space, time & energy, and they're all candidates to go a bit wobbly beyond an EH</>
You have hit exactly on the nail head, of why I had to end a lot of my confusion, and simply realize that when you are dealing with eleven or more dimensions(one part of the theories postulated), then only math can help explain what is going on - and even then, more than one result could simultaneously exist.
I can only hope that new tools will at least let us see further into the mystery, and wish the mission good luck. First they have to have a successful launch - I don't see considering a failure to reach mission posture though - we will keep trying anyway - as curiosity kills the cat, or doesn't (depending on where
Schrödinger went :-) )
I asked the people at the Rochester Institute of Technology about what happens. They have been doing calculations of colliding spinning black holes for years. According to their calculations the angular momentum of the orbiting black holes and the angular momentum of the spinning black holes themselves all radiate gravitational waves preferentially in one direction and the resulting merged black hole is kicked in the opposite direction at a good fraction of the speed of light. Black holes are not necessarily spherical and after a collision there is a "ring down" phase when the resulting merged black hole oscillates for a while. During the last orbit of the black holes (before merging) the spins of the black holes can flip by a large amount.
I wouldn't want to be near such an event - the first one detected radiated more gravitational energy than the entire universe emitted at all frequencies!
"We now have two ways of detecting black holes..."
Not exactly. We have the old school method: spotting the tell-tale X-Ray signature (from the swirling accretion disk).
This new, gravity wave, method doesn't find existing black holes. Rather, it locates empty spots where black holes used to be. Or the place remnants were ejected from.
"The shift between short and long wavelengths will show if the gravitational waves from super kicks are being directed towards or away from Earth."
The wave we detect is always directed at Earth, otherwise we wouldn't be able to detect it. What a Doppler shift would show is whether the source is moving towards Earth, or away from it.
Since I was a kid I have been reading about black holes, the most awesome vacuum cleaner in the Universe. I have been repeatedly told that nothing, not even light, can escape the Singularity.
Now I am being told that, in a collision between two black holes, "remnants" are being flung out. Remnants? From a Singularity ? That infinitely compressed zone of matter that has compressed itself out of our Universe ?
DIV / 0 - DOES NOT COMPUTE
<shutdown>
I don't know whether the use of 'remnants' is due to a poor understanding or a poor choice of words, but I read it as the energy lost during collision. The LIGO observation announced in February was a signal of two black holes merging, with about three solar masses worth of energy being emitted as gravitational waves.
In that sentence, 'remnants' basically reads as "matter kicked out by forces resulting from a merger of two or more black holes".
Nothing came out of the singularity as such - the gravitational waves are a result of mass being transformed into energy by the massive forces involved in a merger of two singularities and their accompanying matter within the event horizons.
They in turn seem to have an effect on the matter sucked within the event horizons of the merging black holes, but not part of either singularity, which causes the kick and for 'remnants' to escape as a result.
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