Primordial Black Holes, Dark Matter and Stellar Collisions… Oh, My!


Well, we’re off to see the Wizard again, my friends. This time it’s to explore the possibilities of primordial black holes colliding with stars and all the implications therein. If this theory is correct, then we should be able to observe the effects of dark matter first hand – proof that it really does exist – and deeper understand the very core of the Universe.

Are primordial black holes blueprints for dark matter? Postdoctoral researchers Shravan Hanasoge of Princeton’s Department of Geosciences and Michael Kesden of NYU’s Center for Cosmology and Particle Physics have utilized computer modeling to visualize a primordial black hole passing through a star. “Stars are transparent to the passage of primordial black holes (PBHs) and serve as seismic detectors for such objects.” says Kesden. “The gravitational field of a PBH squeezes a star and causes it to ring acoustically.”

If primordial black holes do exist, then chances are great that these type of collisions happen within our own galaxy – and frequently. With ever more telescopes and satellites observing the stellar neighborhoods, it only stands to reason that sooner or later we’re going to catch one of these events. But, the most important thing is simply understanding what we’re looking for. The computer model developed by Hanasoge and Kesden can be used with these current solar-observation techniques to offer a more precise method for detecting primordial black holes than existing tools.

“If astronomers were just looking at the Sun, the chances of observing a primordial black hole are not likely, but people are now looking at thousands of stars,” Hanasoge said.”There’s a larger question of what constitutes dark matter, and if a primordial black hole were found it would fit all the parameters — they have mass and force so they directly influence other objects in the Universe, and they don’t interact with light. Identifying one would have profound implications for our understanding of the early Universe and dark matter.”

Sure. We haven’t seen DM, but what we can see are galaxies that are hypothesized to have extended dark-matter halos and to study the effects the gravity has on their materials – like gaseous regions and stellar members. If these new models are correct, primordial black holes should be heavier than existing dark matter and when they collide with a star, should cause a rippling effect.

“If you imagine poking a water balloon and watching the water ripple inside, that’s similar to how a star’s surface appears,” Kesden said. “By looking at how a star’s surface moves, you can figure out what’s going on inside. If a black hole goes through, you can see the surface vibrate.”

Using the Sun as a model, Kesden and Hanasoge calculated the effects a PBH might have and then gave the data to NASA’s Tim Sandstrom. Using the Pleiades supercomputer at the agency’s Ames Research Center in California, the team was then able to create a video simulation of the collisional effect. Below is the clip which shows the vibrations of the Sun’s surface as a primordial black hole — represented by a white trail — passes through its interior.

“It’s been known that as a primordial black hole went by a star, it would have an effect, but this is the first time we have calculations that are numerically precise,” comments Marc Kamionkowski, a professor of physics and astronomy at Johns Hopkins University. “This is a clever idea that takes advantage of observations and measurements already made by solar physics. It’s like someone calling you to say there might be a million dollars under your front doormat. If it turns out to not be true, it cost you nothing to look. In this case, there might be dark matter in the data sets astronomers already have, so why not look?”

I’ll race you to the door…

Original Story Source: Princeton University News. For Further Reading: Transient Solar Oscillations Driven by Primordial Black Holes.

31 Replies to “Primordial Black Holes, Dark Matter and Stellar Collisions… Oh, My!”

  1. It feels like an out of nowhere idea. Like golden bricks under my keyboard. 😀 Why would we have a PBHs in our galaxy? What do we know about them? Why wouldn’t be a star eaten normally?

  2. These observations should put a lower bound on the amount of dark matter that is in the form of black holes. There is a problem with the hypothesis that dark matter is composed of black holes. The entropy of the universe would be much higher than what is possible. The Bousso bounds would not work right.

    As it says this is worth looking into, for nature can in the end surprise us. And if we are not surprised we can get some lower bounds on the percentage of DM that might be in the form of black holes.


  3. Yo Tammy, you’ve misspelled Collisions in the title.

    Also, at the second paragraph, in the third line, “visual” should be visualize.

  4. Hi Tammy,

    Love your articles and your style. You are the reason I read UT! In the second line of the second to last paragraph you use the word “the” but I think you meant it to be “then”. As usual, Ivan got to the other typos first. Keep up the excellent work. -Jamie

    1. But Ivan3man didn’t notice that in the 6th paragraph, first line, Tammy wrote PBM, where she surely meant PBH.

      And now I pass the word on to Ivan3man with further news and updates! 😉

      And an almost unrelated Off-Topic: What’s wrong with the display of the number of comments? On the first page they mostly say 0 comments, while there are surely some hidden after the texts. This might be a task for the editors?

  5. The average distance between close stars in our galaxy is some 7 lightyears. This is about 70 trillion kilometers. This is seventy million times greater than the diameter of an average-sized Yellow Dwarf. The likeliness of a primordial black hole hitting such a star by accident is zero. No use to try watching such an event. It is like waiting for the crash of a car that moves straight (but very slowly…) through a wood of trees, each of one meter diameter, separated from each other by 70.000 kilometers.

    1. That is if there was only one PBH, but if there are zillions of them… I mean the same argument would render star collision impossible, albeit they do collide!

  6. I still believe dark matter is total rubbish, an interesting concept to explain away some problems which should be explained entirely differently. Anyway, What would a star/piece of matter care if a black hole is composed of dark matter or visible matter??????!!?!? Are we talking about very small and light black holes here? Otherwise it’s just a huge gravitational force that pulls everything in towards it, visible matter wouldn’t simply not fall towards just it because it’s physical make up is different to that of the visible matter.

    1. Dark matter may be rubbish, but standard cosmology uses it for effect. To show that it is rubbish, you would have to come up with a better (more explanatory and/or simpler) theory which lacks it.

      To simply state that a theory is rubbish when it works or that a theory component is used to “explain away” when it can be used for prediction is (I’m sorry) rubbish.

      I read this as that the PBHs could be components of dark matter. (But not all of it, see lcrowell comments.) A BH wouldn’t be different because its original massenergy differed (which is sort of the point with a singularity), so a star wouldn’t know a difference.

      But our knowledge would differ, since currently we don’t know what DM consists of.

      1. I do not wish to disclose my theories just yet!! Anyway, apologies – I can easily see why that comment might get up one’s nose… Dark matter is used for effect indeed, but as we know there are significant attempts being made to find it! Although I did actually use the word ‘believe’ 😛 if it was found I would be upset for a while I’m sure, but you can’t deny the proof…..
        Check out this article, got me very excited (told Nancy about it but haven’t seen it on here):

      2. I saw that BBC article, “Dwarf galaxies suggest dark matter theory may be wrong”, a few days ago; it’s reminiscent of that sensationalist New Scientist cover title “Darwin Was Wrong”, back in Jan. 2009, which the actual story stated that only the specific details of Darwin’s evolution theory had been shown to be wrong – mainly the shape of phylogenetic trees of interrelated species.

        Actually, the BBC article only states that the Dark Matter theory “may have to be revised” – warm dark matter (WDM) instead of cold dark matter (CDM).

        So, no need to throw the dark matter ‘baby’ out with the bathwater.

      3. Yes… I read the whole article! And I’m not basing my assumptions on anything I’ve read either. Don’t you agree it’s healthy to promote research into other avenues anyway? I won’t be dissuaded by common paths of ‘knowledge’. If DM exists, then so be it. Let us find it! I have reasons for my beliefs and until it is found or my calculations fail – I’m sticking to my guns.

  7. I’m assuming that the PBH is moving too fast to consume much of the star.

    What would happen if a PBH passed through Earth?

  8. I just got a $827.89 iPad2 for only $103.37 and my mom got a $1499.99 HTV for only $251.92, they are both coming tomorrow. I would be an idiot to ever pay full retail prîces at places like Walmart or Bestbuy. I sold a 37″ HTV to my boss for $600 that I only paid $78.24 for.
    I use

  9. Since we’ve found no PBH’s and we are only speculating as to their probable properties, who’s to say what size they might be, and how fast they might be travelling. I assume that a slower collision might just end up with the star being rather violently torn into a rotating disk of fire before being hurled into a whip of cooling gas as the PBH carries on. Also, have we the means to see star quakes? Even Proxima Centauri is but a dot in the best telescopic fields. Anyone know how long it might take for a 1-5 solar mass PBH to suck up a star like our own?

  10. so why those ripples won`t form when a planet would be swallowed by a star ? Or a comet of a specific composition ?

  11. This attempts to answer some questions posed here:

    Dark matter is just a term used to refer to the observed facts about galaxy rotation. There must be some form of mass other than luminous stars and nebula which gives the profile of orbital velocities of stars. Hence it is called dark matter because it does not appear in forms which produce or re-radiate light.

    Planets would not produce the same effect because they would be vaporized long before they get very far into the body of the star. They of course might produce some wave dynamics on the stellar photosphere at impact, but they would not make it to the other side to produce the mirror wave (it looks similar to a release shock wave).

    Primordial black holes raise problems with the initial entropy of the universe. They can’t form during the inflationary period where particles are being exponentially hurled apart as well as space itself. Prior to inflation, at around 10^{-30}sec, if the universe contained primordial black holes it would mean there is a larger entropy to the initial universe than what might be expected. Of course the big question in cosmology is, “why was the initial entropy of the universe so low?” The most likely answer is that if it were higher the inflationary process would have been less “smooth” and the universe today would have a much higher entropy than we now observe. However, that is a posterior answer, not a fundamental answer which connects to the quantum mechanics of cosmo-genesis.

    The mass of primordial black holes is problematic as well. They would have to be more massive than ~ 10^{11}kg to persist today. Given that rock has a density of about 5g/cm^3, which is comparable to an asteroid of 210m in radius, anything smaller than this would have decayed by Hawking radiation by now. A primordial black hole of say 10^{12}kg would still exist today, but I doubt it would have much measurable impact on the dynamics of a star. A primordial BH with the mass of the moon would of course have an impact, and the paper focuses on PBHs of 10^{17}g or more and up to 10^{26}g. If a significant amount of matter in the early universe were bound up in PBHs it would mean the early universe had entropy not significantly less than it is today.


  12. Tammy, the last sentence of the first paragraph reads: “If this theory is correct, then we should be able to observe the effects of dark matter first hand – proof that it really does exist – and deeper understand the very core of the Universe.” The last section of this sentence should say something like “and deepen our understanding of the very core of the Universe” or “and give us a deeper understanding…” or “and more deeply understand the very core of the Universe.”

    1. Yeah, I had noticed that odd grammar as well, but I did not want to say anything because I figured that, after pointing out the misspelling in the title (my comment was deleted afterwards!), I had irritated Tammy enough already!

  13. “and astronomers could use the researchers’ model to finally observe the elusive black holes. “
    Observing a simulated black hole on a movie screen is not the same as the real thing. You can simulate anything you like in a computer, using your own methods, concepts and equations.
    Basicaly you are creating what you want to see and not necessarily the reality. Here is a real black hole test.
    Black holes should outshine any star in the sky, but we don’t see such objects, because they don’t exist!
    A simple test to detect black holes( if they exist) is to base it on the good old concept of the bending of star light around a massive body. And in this case if that massive body is a BH we should see a halo of back ground stars projected all around the alleged BH position because of the extreme light bending close to the event horizon. Every star on one side of the BH should produce an image on the other side of the BH. Some of the star light approaching directly the BH will be absorbed and some of the star light skimming tangentially near to the event horizon will be severely deflected many degrees, even 360 degrees or even orbit multiple times before heading out.
    This means a BH will swing round the light from every star in the foreground or background of the sky to be seen from any direction that we observe. Therefore, if they exist, BHs must out shine any other bright star in the sky. Specially, the SMBH that is alleged to exist at the center of many galaxies is surrounded by all the stars of the galaxy and therefore if they exist shoud shine brightly. If the BH is far away it should at least shine like a bright star, if it is close by to discern a small angular disc then we should see a black spot in the middle of the apparent bright object.
    Tissa Perera

    1. I think you are overestimating the effect. This light bending is actually pretty weak.
      And anyhow, there is much (and I mean MUCH) evidence that black holes do exist.

      And lastly, although I am more an analytical guy, numerical calculations usually use real physical formulas, and just set other conditions. If you want to know more, I am quite sure the authors in the paper linked by Ivan3man say what they did, and how they come to their conclusions.

  14. What impact would this passage have on the stellar neutrino emission rate? Can we quantify that and postulate any other impacts such as neutrino mix change….

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