When 2 black holes collided

[alpal]

Hi All,
this finding is almost unbelievable but it's from - I hope -
a reliable source.

see this video from Jerome Gauntlett -
professor of theoretical physics at Imperial College.
jump to 34:30
https://www.youtube.com/watch?v=laKp1XeEF74

As measured by LIGO -
the Laser Interferometer Gravitational-Wave Observatory -

when 2 black holes collided -
one was 36 solar masses, the other 29 solar masses -
3 solar masses were lost in gravitational energy -
in less than 1 second which is
more power than is emitted by all of the stars not
just in our galaxy but in all of the galaxies in the universe.

cheers
Allan

[alpal]

OK -
so let's look at this in a hypothetical situation.
Let's say a solar system identical to our own solar system was orbiting
the 2 black holes involved in that titanic release of energy.
What would have happened to that solar system?


What about if there was a star 4 light years away from it like Alpha Centauri?
What would happen to that star?


cheers
Allan

[alpal]

I was trying to think about what would happen when a gravitational wave
with the power of 3 solar masses went through a planet in what would be only a few milliseconds -
43 milliseconds for our earth -
as it's traveling at the speed of light.
I have a feeling it would cause a giant earthquake? -
but I can't quite prove it.
Maybe the pulse is too quick to do anything?
I hadn't thought about radiation yet - would there be a burst of radiation?

Maybe the black holes would direct all the radiation inwards?


I wish Prof. Jerome Gauntlett would have gone into a bit more detail.

[ChrisD]

At the very least you're going to have to reject that current sub due to gravity distortions.

Chris

[alpal]

I found an answer.


https://www.forbes.com/sites/startswithabang/2020/02/15/ask-ethan-could-gravitational-waves-ever-cause-damage-on-earth

By Ethan Siegel
Ph.D. astrophysicist, author, and science communicator, who professes physics and astronomy at various colleges.


If we consider the first gravitational wave ever seen by LIGO — observed on September 14, 2015 but announced almost exactly 4 years ago today (on February 11, 2016) — it consisted of two black holes of 36 and 29 solar masses, respectively, that merged to produce a black hole of 62 solar masses. If you do the math, you'll notice that 36 + 29 does not equal 62. In order to balance that equation, the remaining three solar masses, corresponding to approximately 10% of the mass of the smaller black hole, needed to get converted into pure energy, via Einstein's E = mc2. That energy travels through space in the form of gravitational waves.

There is an enormous amount of energy emitted when two black holes of masses comparable to these merge; converting three solar masses worth of material into pure energy over a timescale of just 200 milliseconds is more energy than all the stars in the Universe give off, combined, over that same amount of time. All told, that first gravitational wave contained 5.3 × 1047 J of energy, with a peak emission, in the final milliseconds, of 3.6 × 1049 W.


There are some ways that a large-enough amplitude gravitational wave could meaningfully impart energy to Earth. Crystals packed in intricate lattices would heat up all throughout the Earth's interior, potentially cracking or shattering if the gravitational wave is strong enough. Earthquakes would ripple throughout our planet, cascading and overlapping, causing worldwide damage on our surface. Geysers would erupt spectacularly and irregularly, and it's possible that volcanic eruptions would be triggered. Even the oceans would produce global tsunamis, disproportionately affecting coastal areas.

But a black hole-black hole merger would need to take place within our Solar System for that to happen. From even the distance of the nearest star, gravitational waves would pass through us almost completely unnoticed. Although these ripples in spacetime carry more energy than any other cataclysmic event, the interactions are so weak that they barely affect us.

[ChrisD]

Hmm, if 2 black holes were in our solar system there may be more to worry about than earthquakes and tidal waves?

I wonder how they can estimate the masses of the 2 black holes before the merger? Is it through numerical analysis or from simulations?

Chris

[alpal]

Imagining our planet close to those 2 colliding black holes
was just an interesting hypothetical question.


I'm not sure how they worked out the before and after masses.