When I first loaded the article all of the images were black, and I thought it was just a joke. Then after about 30 seconds they started filling in with actual pictures...
Most images of black holes are illustrations. Here’s what our telescopes capture
101–110 of 167 posts
Re: Most images of black holes are illustrations. Here’s what our telescopes capture
#102Earlier quoted context omitted.
From our external perspective, they never happen. The time they use to happen in doesn't exist.
So, in our reference frame, black holes never grow from original collapse and remain in that same state, tiny mass and size, no matter what falls into it. Wait, no. It loses mass through particle emission, which is assumed to actually happen. This puzzle was worth investigating when I learned this topic (not sure I understood all math and concepts correctly though).
I mean, the real answer is "black holes are very complicated" and a full explanation is out of scope for a HN comment. Hawking radiation requires a lot of background knowledge to understand (and I have to admit I still don't fully understand it). The pop-sci explanation of particle/anti-particle pairs appearing on either side of the event horizon is incorrect.
Re: Most images of black holes are illustrations. Here’s what our telescopes capture
#103Earlier quoted context omitted.
> It is theoretically possible that the black hole is still performing fusion, and emitting light and heat, like a regular star. I don't think that's a useful picture. It's closer to the truth to say that from the outside perspective, all the information and energy sits on the border and there is not even an inside to speak about. In other words, it's the edge of the universe and what's past the event horizon is anot…
To me, the concept that there is another universe, beyond the Event Horizon, is a little silly. However, for fun, I once thought of a science fiction scenario for a novel. I thought a Black Hole, can be used as the instrument for a wormhole in space. An Einstein-Rosen Bridge, that connects our universe to another universe, in the multiverse. But there are a lot of plot holes in this idea. If light cannot escape the b…
Ah, that story when realistic physics happened and she loves him. First question, lasers or blasters? Second, is good guy’s dad bad guy?
Third, probably least interesting, how does one get into BH travelling FTL, if that makes you go back in time?
Re: Most images of black holes are illustrations. Here’s what our telescopes capture
#104Earlier quoted context omitted.
Great comment -- but while I agree w/ your point about metaphors, I respectfully mildly disagree about this one in particular. For context, I associate it with the popular analogy of timespace as an elastic "sheet" of sorts, with marble-like objects resting on (and sinking into) its surface, with their mass dictating how "deep" their gravity "well" is. With that metaphor in mind, black holes really do approximate hol…
I don't like the elastic sheet analogy because it doesn't work without gravity, the very thing it's attempting to explain.
This has always bothered me as well, and I'm surprised that this is the first time I've seen anyone else mention it!
Re: Most images of black holes are illustrations. Here’s what our telescopes capture
#105Earlier quoted context omitted.
Aren't the detected gravitational waves evidence that black holes exist? I mean, don't the waves measure a merge up to the point that both black holes are inside a single Schwarzschild radius? And if so, isn't that very strong evidence that the things merging are black holes?
Gravitational waves are evidence, two extremely large objects merged, not that a black hole was formed. EDIT: If our instruments were precise enough and we could remove the noise, we could theoretically detect gravitational waves of two Sun sized stars merging (2 solar masses shouldn't form a star capable of becoming black hole).
But they can tell the distance between centers of mass and total mass. Haven't we observed that distance shrink until it reaches their Schwarzschild radius?
(I really don't know the answer.)
Re: Most images of black holes are illustrations. Here’s what our telescopes capture
#106Earlier quoted context omitted.
I think you’re confusing the lack of knowledge of whether or not singularities really form, with whether or not black holes form. There are very clearly black holes, but of course we can have no way of knowing if they contain singularities. Quark stars could exist, it not with the masses observed in Sag A*. Quark degeneracy pressure isn’t going to support the mass of millions, or even billions of suns. It might be th…
What's a black hole without a singularity? A neutron star? Is there a distinction you are making? To me a black hole and a singularity are the same thing. Are you using a different definition? > Quark degeneracy pressure isn’t going to support the mass of millions, or even billions of suns. Why not? If the star is very large the density (and thus gravity) never get high enough. For example, if you consider the milky…
> What's a black hole without a singularity?
A black hole with a lumpy interior. (It does not have to be always lumpy).
Consider two black holes of the type you envisage, where the mass and charge of each is entirely at the singularity point of each black hole. Let the black holes merge. How do two singularities become one singularity?
Re: Most images of black holes are illustrations. Here’s what our telescopes capture
#107Every time I read articles like this I feel bad about my career choice. How could anything I do compare to the fascination of space exploration? The universe we live in is nothing short of mind-boggling. I'm thankful that I can at least marvel at nebula pictures taken by Hubble. However, I wish they'd switch goals from getting a few people to another planet to getting imaging equipment there that is capable of formin…
But then who would deliver the ads?? /s
I completely agree, but with the arts as my object of fixation. I could never live the swanky life I lead without my current job, but damn I would have been a good potter. Luckily, there is still time...
Re: Most images of black holes are illustrations. Here’s what our telescopes capture
#108Keep in mind as well that no observation has yet distinguished between a neutron star and a black hole. i.e. all those photos of super massive objects could be neutron stars, and we would not be able to tell the difference. They are assumed to be black holes because of the mass, but if there is something in the law of physics that prevents black holes from forming we would not know. We do not have a theory on quark d…
> Keep in mind as well that no observation has yet distinguished between a neutron star and a black hole.
No, that's wrong.
Narayan, R. and McClintock, J.E., New Astronomy Reviews, 51, 733–51, 2008 [arxiv: https://arxiv.org/abs/0803.0322 ] has a beautiful chart (Fig. 8) comparing the quiescent bolometric luminosity of star-to-accreting-neutron star binaries and star-to-accreting-black hole binaries. Observed NS binaries are brighter than observed BH (candidate) binaries.
This is one test for whether a compact accretor in a binary is a BH rather than an NS.
This technique was used by Bennett et al., 2002 and Mao et al., 2002 to find several candidate BHs.
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Bennett, D.P., Becker, A.C., Quinn, J., et al. (2002). Gravitational microlensing events due to stellar-mass black holes. Astrophysical Journal, 79: 639–59.
Mao, S., Smith, M.C., Woz ́niak, P., et al. (2002). Optical Gravitational Lensing Experiment OGLE-1999-BUL-32: the longest ever microlensing event—evidence for a stellar mass black hole? Monthly Notices of the Royal Astronomical Society, 329: 349–54.
Re: Most images of black holes are illustrations. Here’s what our telescopes capture
#109Earlier quoted context omitted.
Aren't the detected gravitational waves evidence that black holes exist? I mean, don't the waves measure a merge up to the point that both black holes are inside a single Schwarzschild radius? And if so, isn't that very strong evidence that the things merging are black holes?
Gravitational waves are evidence, two extremely large objects merged, not that a black hole was formed. EDIT: If our instruments were precise enough and we could remove the noise, we could theoretically detect gravitational waves of two Sun sized stars merging (2 solar masses shouldn't form a star capable of becoming black hole).
This is not correct, the nature of gravitational waves emitted by the merging of two objects is different in its final stage, depending whether the objects form a black hole or not. Until a black hole is formed, the nature of the emission is the same for all objects (e.g. black holes or neutron stars), but if a black hole forms, the final emission (ringdown) is different.
The first LIGO-Virgo events detected black hole mergers which resulted in black holes.
The last LIGO-Virgo event detected two neutron star mergers. Unfortunately the sensitivity of the apparatus is not good enough to determine if the merge resulted in a black hole, or a neutron star based purely on gravitational wave measurements. However, we have secondary evidence[1] that the remnant was a black hole.
Re: Most images of black holes are illustrations. Here’s what our telescopes capture
#110If the speed of light of this universe was raised significantly, is there some point where black holes would be impossible to form? I assume if the speed of light were lowered black holes would become far more common?
Yeah but if you do that, then you'll get a universe that's not this universe. Speed of light affects much of physics and causality.
Hard to imagine how different the resulting universe might be, what if the speed of light and causality were say 10x higher than what it is now? Or what if the speed gradually increased over time? Would we just evaporate?