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0 pointskrylon8y ago0 comments

Huh. IIRC, black hole mergers are also a likely source of short gamma ray bursts. So I suspect at 1 AU, one would need a lot of shielding to not get fried by the gamma rays.

EDIT: What I meant to say was: It would probably be quite awesome to experience such an event up close, provided it is possible to do so safely. ;-)

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dwaltrip8y ago

I believe that black hole mergers are dark in the entire electromagnetic (EM) spectrum. This is why the recent binary neutron star merger was so groundbreaking -- it emitted both gravitational waves and a broad spectrum of EM waves.

Indeed, though, it would be awesome to witness the collision and resulting gwaves personally, if such a thing was possible :)

raverbashing8y ago

Nah I think there are some effects in the visible range. You probably have some kind of accretion disk that gets shaken up by the merger, there might also be some effects due to Hawking radiation

But they're probably only visible from close range (like the 1AU mentioned above) and are too faint to be seen from 1Bi light years like the event that they captured

russdill8y ago

That's assuming they are "naked" and not surrounded by rotating disks of gas and dust.

dwaltrip8y ago

AFAIK, only supermassive black holes at the center of galaxies have disks of material that is falling inward (and emitting significant amounts of light in the process). Even then, they only actively feed in that way for a short period of time -- I think something like 10k years.

All of the LIGO observations have been of more basic stellar mass black holes merging together.

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krylonOP8y ago

> I believe that black hole mergers are dark in the entire electromagnetic (EM) spectrum.

Now that I think about it - yes, of course. It's why they are called _black_ holes. ;-) facepalm

vecter8y ago

That doesn't follow from the fact that black holes are "black". For example, black holes can emit a ton of radiation from accretion disk as matter accelerates and falls inwards, radiating huge amounts of energy [0]. Two naked black holes merging probably wouldn't emit much (if any) EM radiation, but if they had very active accretion disks, then it's certainly possible there would be a ton of EM activity.

[0] https://en.wikipedia.org/wiki/Accretion_disk

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antognini8y ago

Gamma-ray bursts were believed to be due to mergers of two neutron stars, not black holes. LIGO's observation of a NS-NS merger coincident with a gamma-ray burst has strongly confirmed this picture.

krylonOP8y ago

I see. In the back of my mind there was still the possibility that it could have been created by two black holes merging or a neutron star falling into a black hole.

... I wonder, if a neutron star and a black hole merge, does the neutron star get shredded early enough to form an accretion disk, or does it just disappear like a marble falling into a hole?

For some reason my imagination is quite lively today, these questions just keep popping up in my head like banner ads. ;-)

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dwaltrip8y ago

Indeed, though, it would be awesome to witness the collision and resulting gwaves personally, if such a thing was possible :)

raverbashing8y ago

Nah I think there are some effects in the visible range. You probably have some kind of accretion disk that gets shaken up by the merger, there might also be some effects due to Hawking radiation

But they're probably only visible from close range (like the 1AU mentioned above) and are too faint to be seen from 1Bi light years like the event that they captured

russdill8y ago

That's assuming they are "naked" and not surrounded by rotating disks of gas and dust.

dwaltrip8y ago

All of the LIGO observations have been of more basic stellar mass black holes merging together.

2 more replies

krylonOP8y ago

> I believe that black hole mergers are dark in the entire electromagnetic (EM) spectrum.

Now that I think about it - yes, of course. It's why they are called _black_ holes. ;-) facepalm

vecter8y ago

[0] https://en.wikipedia.org/wiki/Accretion_disk

1 more reply

antognini8y ago

Gamma-ray bursts were believed to be due to mergers of two neutron stars, not black holes. LIGO's observation of a NS-NS merger coincident with a gamma-ray burst has strongly confirmed this picture.

krylonOP8y ago

I see. In the back of my mind there was still the possibility that it could have been created by two black holes merging or a neutron star falling into a black hole.

... I wonder, if a neutron star and a black hole merge, does the neutron star get shredded early enough to form an accretion disk, or does it just disappear like a marble falling into a hole?

For some reason my imagination is quite lively today, these questions just keep popping up in my head like banner ads. ;-)

j / k navigate · click thread line to collapse