How Can Black Holes Shine?

We hear that black holes absorb all the light that falls into them. And yet, we hear of black holes shining so brightly we can see them halfway across the Universe. What’s going on? Which is it?

I remember back to a classic episode of the Guide to Space, where I provided an extremely fascinating and concise explanation for what a quasar is. Don’t recall that episode? Well, it was super. Just super. Alright slackers, let’s recap.

Quasars are the brightest objects in the Universe, visible across billions of light years. Likely blanching life from everything in the path of the radiation beam from its lighthouse of death. They occur when a supermassive black hole is actively feeding on material, pouring out a mountain of radiation. Black holes, of course, are regions of space with such intense gravity where nothing, not even light itself, can escape.

But wait, not so fast “recap” Fraser Cain. I call shenanigans. If black holes absorb all the radiation that falls into them, how can they be bright?

You, Fraser Cain of days of yore, cannot have it both ways. It’s either a vortex of total destruction gobbling all the matter and light that fall into them OR alternately light can escape, which still sounds good. I mean, it could be WHERE NO STUFF CAN ESCAPE, except light.

If you’ll admit that you of the past was wrong, we’ll put you in the temporal cone of shame and move on with the episode. Right? Right? Wrong.

Let’s review. Black holes are freaky complicated beasts, with many layers. And I don’t mean that in some abstract Choprian “many connections on many different levels”. They’re a gobstopper from a Sam Neill Event Horizon style hellscape. Let’s take a look at the anatomy of a black hole, and everything should fall into place, including the terror.

At the very heart of the black hole is the singularity. This is the region of compressed matter that used to be a star, or in the case of a supermassive black hole, millions or billions of times the mass of a star. Astronomers have no idea what the singularity looks like or behaves, because our understanding of physics completely breaks down, along with the rest of our brains.

Illustration of Cygnus X-1, another stellar-mass black hole located 6070 ly away. (NASA/CXC/M.Weiss)
Illustration of Cygnus X-1, another stellar-mass black hole located 6070 ly away. (NASA/CXC/M.Weiss)

It’s possible that the singularity is a sphere of exotic matter, or maybe it’s constantly compressing down into an infinitely small size. It could also be a pork pie. We’ll never know, because nothing goes fast enough to escape from a black hole, not even light.

Maybe you’d need to be going 10 times the speed of light to escape. Or maybe a trillion times the speed of light. Which makes it easy; as far as we can tell, nothing can go faster than the speed of light, and so nothing is escaping.

As you get further from the singularity, the force of gravity decreases. Initially, it’ll still requires that you go faster than light. You’ll finally reach a very specific point where the escape velocity is exactly the speed of light. This is the event horizon, and it’s a different distance from the singularity with every black hole. That’s the line. Within the event horizon, the light is doomed, outside the event horizon, it can escape. This is the hard candy shell surrounding the chocolately unimaginable nightmare of physics.

So when see bright black holes, like a quasar, we’re not actually seeing light coming from inside the black hole itself or reflected of its surface. What we’re seeing is the material that’s piling up just outside the event horizon. For all its voracious hunger, a black hole’s gravitational eyes are much bigger than its stomach, and it can only feed so quickly. Excess stuff piles up around the black hole’s face and forms a vast disk of material, just like me at a Pizza Hut’s $5 all you can eat buffet. This pizza heats up until it’s like the core of a star, and starts blasting out radiation into space.

A WFPC2 image of a spiral-shaped disk of hot gas in the core of active galaxy M87. HST measurements show the disk is rotating so rapidly it contains a massive black hole at its hub.
A WFPC2 image of a spiral-shaped disk of hot gas in the core of active galaxy M87. HST measurements show the disk is rotating so rapidly it contains a massive black hole at its hub.

Everything I’ve said is for non-spinning black holes, by the way. Physicists will always make this point with great emphasis. Stay your angry comments astrophysicists, for I have said the magic stone-cutter appeasement code-word, “Non-rotating”.

Of course, black holes do rotate, and can rotate at nearly the speed of light. And this rotation changes the nature of the black hole’s event horizon in ways that make difficult math even harder. All this spinning generates powerful magnetic fields around the black hole, which focuses jets of material that blast out for hundreds of thousands of light-years. When we see these bright quasars, we’re staring right at these jets with our delicate little eyeballs.

So how can we see light coming from black holes when black holes absorb all light? It’s not coming from black holes. It’s coming from the super-heated region of junk all around the black hole. And still, anything that falls through the event horizon, whether it be light, junk, you, me or Grumpy Cat it will never been seen again.

What’s your favorite sci-fi black hole? Tell us in the comments below.

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29 Replies to “How Can Black Holes Shine?”

  1. Classically, accelerating a charge will cause it to radiate (read “give off light”), thus as charged particles accelerate towards the black hole, they should radiate — visibly, because the light is not close enough to be captured.

    Unclassically (no, that’s not a word) climbing out of a grey hole (almost a black hole) should take a lot of energy out of a photon. Thus, I would expect that, for example, an ultraviolet wave could end up as an infrared wave. In fact, maybe a “black hole” is just a very deep-reddening hole (microwave hole, whatever).

    1. Hello Frazer, maybe there is something we can know about the singularity. As matter spirals in to the center, the centrifugal forces should increase, as the orbit gets smaller and rotation speed increases, so, question for astrophysicists: is there a limit where the centrifugal forces would be equal to the gravitational pull, so that the singularity can’t collapse to A smaller volume?

    2. What is it that this site always attracts crazy Electric Universe nutters?

      Look: Plasma, must be magic.
      Look: Plasma, must be space copper wires.
      Look: Plasma, lest ignore the fact that positive ions in space do not exists and that they cancel out any negative ions in space.
      Look: Plasma, lets ignore that ions of the same charge hate each other and wants to get away from each other as fast as possible.

      If you are one of these EU believers then it is a big sign that you have a chronic lack of understanding basic physics. EU is a religion, not science.

      1. Because they don’t think that the peer reviewed science journals are good enough?

        Canadian Institute for Theoretical Astrophysics (CITA) actually publishes many lectures online about electromagnetism on astronomical (but not intergalactic) scales. Search them on youtube, I won’t post any link here. I can’t judge the validity of their science, I hope it is very different from the EU fraudsters online.

        EU is thriving because of the havoc of the 400 years old gravity theory. The missing mass mystery, that Kepler’s laws, the foundation of astrophysics, don’t apply to galaxies. Something’s gotta give in the established models, and everyone takes the opportunity to argue for his favourite substitute. When the most reputable scientists can’t come up with anything better than dark matter, the step down to fraudsters looks smaller than ever.

      2. The EU proponents are the equivalent of creationists.

        Science can’t explain life: therefore “God did it”.
        Accompanied with tons of bible quotes that proves that God did it.

        Science can’t explain missing mass therefor “EU did it”.
        Accompanied with tons of plasma quotes that EU did it.

        EU falls flat on its face the moment you asks to show some maths and some numbers.
        e.g. Comets are charged, that is an EU claim.
        Now I ask: HOW MUCH charge?

      3. Electric comets have some history in human fantasy. “Edison’s Conquest of Mars” was an (unsolicited and really bad) 1898 follow up on “War of the Worlds”. Thomas Edison invents a way to travel between the planet’s using their magnetic fields, and gets trapped by a passing electric comet. And already Johannes Kepler speculated that magnetism might be the force which keeps the planets in orbit, before Galileo came up with the idea of gravity.

    3. This type of suppression is exactly what one would expect from a someone that is disseminating information that is incorrect. What’s wrong? Afraid to hear that there are more rational explanations for the observations about which you preach gospel???? Guess so.

      1. Your ‘comment’ was deleted because, despite numerous attempts (on other threads) by various commenters to point out to you the fact that it is only at the quantum level that electromagnetism is 10^36 times more powerful than gravitation, you have continued to regurgitate the same damn rubbish that you have learned parrot-fashion from “Electric Universe” websites onto every new article on UT about black holes, dark matter/energy, and (the “Electric Universe” pet subject) magnetic fields!

      2. Finding one or two specific examples where you believe I am incorrect is a reason to suppress the 20-30 salient and correct points that I have made? You must realize that all it takes is the truth to eventually emerge and your house of cards will come tumbling down. Then your field of expertise will be relegated to the fantasy that it is most surely.

      3. The above example was not the only reason for the deletion of your (yet another rambling) comment; it was deleted because of your persistent promotion of books by “Electric Universe” proponents – and that’s advertising!

      4. What a crock….I mention one academic book which details the points I was making and you suppress my entire comment. Man, you guys must be frightened to death. I guess you see the end of the road coming. It’s not to late to change your “beliefs”.

  2. The theory of Black Holes (like Evolution) don”t square. All the explanations sound scientific alright but don’t make any sense whatsoever. Has anyone SEEN a Black Hole?

    1. We are measuring it:

      “Best view yet of dusty cloud passing galactic center black hole”

      We can also see the effects of a black hole on space through gravitational lensing:

      So yes we have enough evidences that they are real.

      The fact that the mathematics do not line up well does not mean that they do not exists but that our mathematics tools are incomplete.

  3. Perhaps all blackholes — regardless of size — have a uniform blackhole density [BHD] throughout … sort of like a malted-milk ball. Perhaps BHD is yet another universal constant as is the speed o’ light: nothing is denser than BHD. Consequently, there would be no so-called “singularity” at the very center of a blackhole.

    1. In our frame of reference, black holes never form. When an object reaches 99.9+% of the mass needed to become a black hole, the relativistic effect of its mass is so large that all objects moving into it simply stand still and never cross the event horizon. And the event horizon is thus never created because the black hole is never created.

      The star remnant will be some kind of a super neutron star quark porridge, but never a black hole. It will never receive that extra 0.01% mass to cross the border. It takes an eternity for any more mass to cross that last nanometer through its shell. And in the mean time Hawking’s radiation will evaporate the object which almost, but never, became a black hole.

      But that’s just how we see it. Those down there in the hole actually really do cross the event horizon. What you experience depends on where you are. That’s weird, but already Kepler 400 years ago used the frame of references as he recognized that the Ptolemaic, Copernican and Tychonic systems of the planetary motions were are mathematically identical, their only difference was their choice of frame of reference. Physics was weird from the beginning, and that makes it plausible for anyone who honestly considers everyday life. Something weird is definitely going on here. It might very well be physics.

  4. The more Stars a Black Hole consumes the higher the (BHD) I do not believe that (BHD) is a constant like Light Speed the more Massive the Black Hole the Denser The Nucleus, And at the End of Time the Biggest Black Hole will Eat Everything in our Universe including all the other Black Holes (then we have another Big Bang and it All starts again) 🙂

    1. That’s not how it works I’m afraid 😉

      The largest known black holes are the Supermassive Black Holes in galaxies such as Holmberg 15A, but what happens to them once they exhaust their supply of matter in the area surrounding the accretion disc? The prevailing theory is that those which use to be Quasars, Blazars, Seyfert or any type of active galaxy tend to ‘switch off’ when they run out of matter to eat. It would seem to explain objects like Sagittarius A* in our galactic centre.

      Once even the most massive black holes have no ‘food’ to increase their density or mass, they can’t just decide to chow down on other galaxies. As Hubble’s Law shows, galaxies are moving away from one another at approx 72-75km/s depending upon your source. The black hole would have to span the observable universe to ‘eat’ everything. Consider if our Sun turned instantly in to a black hole. Our orbit wouldn’t be affected at all, at least not until some unlucky piece of matter on an eccentric orbit passed within the Schwarzschild Radius. Black holes are intriguing but they aren’t sinkholes, piling everything towards them just because they are a black hole.

      A black hole couldn’t just decide to pull the rapidly expanding universe back towards it once it got sufficiently big for its boots, that’s not how their gravitation works.

  5. So once again I have to ask the question that has never been answered here: Why are black holes always depicted in artists’ conceptions as black disks like an eclipse? With all this energy being produced just outside of the event horizon the entire spherical surface should be incredibly bright.

    BTW, I wonder if we don’t need to reconsider how we think about infinity and singularities. I think these are concepts rather than quantifiable things. A line is a one dimensional concept, not a thing. So it is with infinity and singularities. They are useful mathematical concepts, but not things. When we mix concepts with quantities, that’s when it gets confusing.

    1. Over time, accretion disks tend to become a flat spiral because that is the only direction that does not collide the dust particles with each other. When they collide, some gain energy gets ejected from the black hole, others lose energy and fall into the black hole.

      Energy is only been produced when something falls in. The energy comes from the stored potential energy of the particles that drops in height. No gas, no energy transmitted by the black hole except for hawking radiation.

      Magnetic fields of the gas that gets heated up and becomes plasma also forces the other particles in some disk like structure except very near the event horizon.

  6. Total noob question here.

    I saw that EU guy’s comment and noticed how quickly everyone jumped on him and now the post is deleted. OK I understand that the whole Electric Universe theory has been thoroughly discredited. I get that. No, I’m not going to start a rant about how all you “ignant sheeple” need to get on board the EU train. I’m not pushing a book or anything like that. Clearly the sun is lit by nuclear fusion, not by being a gigantic electric neon bulb.

    But is it possible (and I would like a real answer here, not just a slap to the face) that there is a small grain of truth to EU, in that electricity plays some part in the whole galactic dance? Can we really count it out completely? Surely electricity has to do something on the galactic level, no?

    According to the EU guy’s claim (deleted) the galaxy will hold together using electricity without the need for dark matter or dark energy. Dark matter and dark energy have never really been observed, and both have always seemed like a cosmic cop-out to me. I don’t like these theories. I like them about as much as… as much as the EU theory.

    But electricity IS energy. If electricity contributes something to the bonds holding the galaxy together, is it not possible that this is the dark energy we’ve been looking for? And that it’s cleverly hidden in the one place where no self-respecting cosmologist would dare to look?

    Or here’s a stretch – is it possible that this far out from the galactic core, gravity does 99% of the work holding things together, but as you get closer to the center of the galaxy, electricity plays an ever-increasing percentage?

    Anyway, like I said, I’m new to the whole EU thing and had to do a wiki trail to see how and why it was discredited. So please don’t come after me with torches and pitchforks. I’m just throwing the question out there.

    Has anyone looked into the possibility of a partial-EU solution that might eliminate the need for dark matter and dark energy? Or is that too just wishful thinking and over-simplification?

    1. Thank you Dr. Gadget. At least there is one open minded soul out there.
      The truth of the matter is that the electric universe models put forth by Donald Scott, Wal Thornhill and a host of others are being validated today by the latest radio telescope data.
      For example (and there are far too many examples to mention here), the work of Halton Arp is being validated by the latest data from Chandra. Arp was a radio astronomer that studied under Hubble and at the Max Planck Institute. Hardly a crackpot. He collected a wealth of data (that was published) that showed red shift to be a function of age, not distance or velocity. Carl Sagan said at the time that if this work is confirmed it will invalidate the big bang theory as well as inflation.
      Data from Chandra was received by viewing the Seyfert galaxy NGC 7603 in October 2014. This revealed that there were actually 2 galaxies connected by a large gas cloud. The red shift of one of the galaxies was TWICE that of the second (z=0.057/z=0.029). This is just one of hundreds of contradictions recently obtained which show red shift is not related to velocity or distance. There are literally hundreds of reports showing the same thing.
      As far as the idea that the energy from the sun comes from nuclear fusion occurring in the core there are some seemingly insurmountable problems. These stem from findings by the Voyager and IBEX missions. The first is that the convection velocities were found to be less than 5% of that needed to maintain this theory. This is has yet to be addressed by solar physicists. As second interesting fact recently confirmed by MMS is that charged particles leaving the sun are found to accelerate as they approach Earth. This can only happen in an electric field. The MMS is mapping the complex magnetic fields that exist between the sun and the earth. It should be taken for granted that these magnetic fields must be caused by flowing electric current but they seem to choke a little when this is mentioned. These Birkeland currents are well established and are the source of the charged particles creating the auroras. The overwhelming predominance of magnetic (and therefore electrical) events at the sun’s surface is being made very clear by IBEX and MMS.
      It is a complete mistake to say that the cosmological models put forth by plasma physicists and electrical engineers have been proven not to be correct. It is a fact that mainstream astrophysicists have dismissed them but they have done so without utilizing the scientific method. They have been dismissed out of hand without thorough investigation. Their motive for this is understandable. To acknowledge the validity that is becoming clear today would harm reputations and more importantly livelihoods (grant money). Who wants to admit they have lived a mistake for the last 50 years??
      So the intense anger/emotion surrounding this work and the suppression of these views is easily explainable. The truth, however, will emerge. There are just too many contradictions and failed theories in the standard model for it to survive. The mathematical creation of unobserved reality to salvage these theories will eventually be accepted for what it is….fantasy.
      It will be a slow and painful process. The first real indication that it will happen was when NASA invited Donald Scott to speak at the Goddard Colloquia on Engineering in 2009. The information he presented was straightforward and has influenced the current MMS mission.
      That should be enough to encourage others to take the electric models of cosmology seriously. IMO they are far more scientific than anything offered by the standard model.

    2. The issue with the galactic rotation curves is actually the opposite. The outer regions move faster than you’d expect them to, so the corrections to gravity that you need are more necessary away from the center. Many possible solutions have been proposed. Dark matter is one (and it’s the best candidate IMO). Modifications to the gravitational force (called MOND) are another. Some people have proposed additional, unknown, physical forces and yet others, such as the EU people, suggest unexpected applications of forces that we do know. I, for one, see less difficulty in hypothesizing an elementary particle that experiences only gravity, than a lot of invisible magical dynamos in the sky that produce galaxy-scale electrical currents without any known or plausible power source.

      There is a powerful line of evidence against MOND: the Bullet Cluster. This is a collision between two large clusters of galaxies. We can infer where the center of mass is, based on gravitational lensing of background galaxies. And we can infer where the bulk of the normal matter is, from X-ray observations that show where the gas in the clusters is colliding. And they are not in the same place. Under the dark matter hypothesis, this is easy to explain: two colliding gas clouds affect each others’ motion through gas pressure forces, but the dark matter that was travelling with them does not experience any of those forces, and just continues on unaffected. MOND has a hard time explaining this, and so does the EU hypothesis, since one would expect the electrical forces to be strongest where the matter is colliding.

      The EU people’s escape is to claim that the Bullet Cluster is actually very nearby, in our Local Group. I’m not exactly sure why they think this helps their cause, but it is in any case ridiculous. It would mean that the individual galaxies in the Bullet are teeny tiny scaled down versions of normal galaxies. And for some reason we can’t resolve individual stars within those galaxies, even though we can do so for the other galaxies in the Local Group.

      Astronomers and astrophysicists give electromagnetism its due. We know that this force plays an important role in most astrophysical phenomena. It’s not as though scientists ignore it. It’s just that the EU people want electricity to be the dominant explanation for everything, and this leads them to make claims that just don’t stand up to scrutiny.

    3. @DrGadget,
      I could provide you with numerous links debunking the “Electric Universe” arguments stated above by “btraymd”, but that would take too long, so here’s a good one that debunks the “Electric Sun” model: On the “Electric Sun” Hypothesis.

      1. Stop worrying about dunking the EU theories. Tell me about the lack of convection velocities found in the sun. They were less than 5% of that needed to sustain the model of nuclear fusion in the core. If you see the latest MMS data, the only factors that are involved are tremendous magnetic and electrical fields. But this is due to nuclear fusion in the core, right?

      2. Firstly, you tell me and everyone else here: who or what pays for the astronomical electricity bill to power not only the “Electric Sun”, but also all the other stars in our friggin’ galaxy?!

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