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Black Holes to the Rescue

The views expressed are those of the author and are not necessarily those of Scientific American.


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This post is the fourth in a series that accompanies the publication of my book ‘Gravity’s Engines: How Bubble-Blowing Black Holes Rule Galaxies, Stars, and Life in the Cosmos’ (Scientific American/FSG).

Ten years ago the universe was in trouble.

Or rather, our puny human theories about the nature of all the stars and galaxies in the universe were in trouble. At this time we had managed to discover a number of remarkable things about our cosmic surroundings. We had detected minute non-uniformities in the remains of the primordial radiation field known as the cosmic microwave background, and we had ever more convincing evidence that normal matter – the stuff we are made of – amounts to barely a fifth of the total raw mass of the universe. The rest is dark matter, a shadowy stuff that seldom interacts particle-to-particle but is massive enough that its gravity dictates much of the motion of stars in galaxies and the colossal structures of galaxy clusters and superclusters.

A virtual cosmos. The predicted distribution of stars and galaxies across tens of millions of light years (Credit: Millenium Simulation)

Armed with these observations, and with our models of how these features would translate into the seeding and gravitational growth of structure in the universe, we could build virtual realities in which galaxies and stars would arise and populate an imaginary cosmos. These simulations could then be compared to our great cosmological maps and our statistical counts of all the bright and dark places around us. It was a way to confirm our ideas, compare virtual universes to the real one. And this was the problem, because most of these models did not look quite like the real thing.

The fact was that the simulations overproduced stars and they overproduced big bright galaxies. They didn’t produce a cosmos that looked like ours. Debate raged over the possible cause. It was possible that the computer algorithms used to simulate the production of stars in the virtual galaxies were deeply flawed. It was also possible that we were missing a critical component, a source of additional energy that would dampen down the process in the real universe, stunting galaxies and regulating stellar births from virtual nebula. But what could it be? It might be the energy of the stars themselves – massive suns burning through their nuclear fuel quickly and exploding as supernova could impose a speed-limit on the formation of subsequent generations. It might also be something else that was lurking in the dark alleys and back rooms of the cosmos.

Supermassive black holes had long been suspected of being a disruptive element. As I wrote in the last piece in this series, when they consume matter they can be incredibly noisy, casting energy back out into the surrounding universe. Inside clusters of galaxies we see them blowing bubbles and generating waves in intergalactic gas, phenomena that slow down the condensation of that gas into cool nebula and new stars. In other places we see the wash of radiation and particles flooding galaxies, a sporadic but potent force. It looked like a promising solution, but was still incomplete.

I was personally convinced of the role that these giant holes play in ‘pruning’ galaxies and stars when my colleagues and I stumbled across a great clue in the deep cosmic past. For black holes to provide the missing link, they needed to have helped stunt the growth of the very largest galaxies. And that meant that they needed to have been involved from the very outset, something that was unconfirmed. Luckily, we had discovered just such a situation in a place some 12 billion light years away, in the early morning of galactic evolution.

The birth of a galaxy. An overlay of the X-ray light (blue) and ultraviolet light (red) coming from a system 12 billion years ago (with thanks to Wil van Breugel and Ian Smail)

It has a dreadfully boring name of 4C 41.17. A source of intense radio waves so far away that its light is stretched, redshifted, by a factor of 3.8 due to the expansion of the universe. Using the giant Keck telescope in Hawaii, a seven hour exposure allowed us to make an image of what was originally the ultraviolet light flooding from this system – revealing a tumultuous scene of gas ebbing and flowing. Deep infrared images also showed a colossal mass of star dust, 600 million times the mass of our Sun in carbon-rich grains, a fingerprint of an orgy of stellar birth and death. And then we used NASA’s orbiting Chandra X-ray Observatory for 40 hours to gather the barest whisper of X-ray light, a total of only 150 twelve billion year-old photons. But this was all we needed, because they revealed the whole story.

Deep inside this teenage galaxy was a supermassive black hole. As it consumed matter it was spewing forth electrons at close to the speed of light. As these particles sped away they were meeting the cosmic background radiation, primordial photons. But 12 billion years ago the universe was more compact, the background radiation was warmer than it is today, and so when these encounters happened the exchange of energy was far more efficient than it is today. Black hole accelerated electrons boosted primordial photons into X-rays, and the X-rays were penetrating through the murk of this youthful galaxy, modifying its production of new stars.

It was an exciting discovery. A vivid demonstration that we did indeed need black holes, that they were not mere bystanders in the game of cosmic evolution but central players, today, yesterday, and all the yesterdays before that.

The number of stars in the universe, and the very nature of the galaxies, owes an enormous debt to the behavior of these most extreme and fantastical of astrophysical phenomena. Ten years ago they helped solve part of a mystery, who knows what we’ll learn about them next.

The whole story of our modern view of black holes is told in Gravity’s Engines, available today!

Caleb A. Scharf About the Author: Caleb Scharf is the director of Columbia University's multidisciplinary Astrobiology Center. He has worked in the fields of observational cosmology, X-ray astronomy, and more recently exoplanetary science. His books include Gravity's Engines (2012) and The Copernicus Complex (2014) (both from Scientific American / Farrar, Straus and Giroux.) Follow on Twitter @caleb_scharf.

The views expressed are those of the author and are not necessarily those of Scientific American.



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  1. 1. Raoul 4:12 pm 08/14/2012

    I just know nothing and even that’s for sure

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  2. 2. jtdwyer 1:26 am 08/15/2012

    Caleb – Nicely put! Is it correct to say then that supermassive black holes were removing material and energy from galaxies that would have otherwise resulted in the production of additional stars?

    Also, perhaps you can explain how it was determined “… that normal matter – the stuff we are made of – amounts to barely a fifth of the total raw mass of the universe” and “The rest is dark matter…” Was this proportion arrived at the amount of additional mass required to generally make galactic models produce their observed non-Keplerian rotation curves, or was is the amount necessary for cosmological simulations to produce some observed characteristic? Thanks in advance…

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  3. 3. vinodkumarsehgal 3:08 am 08/15/2012

    Author is attributing the missing mass of stars and galaxies when compared to simulations to the presence of super massive black holes at the center of galaxies. He is also stating that for the black holes to stunt the growth of galaxies, super massive black holes should be associated with the galaxies right from outset.

    In support of above, he has presented a study of an intense radio source nicknamed 4c 41.17 located some 12 billion light years away from earth and having a mass of about 600 million solar masses. An object of such a supermass equivalent to 600 million solar masses should be either a super massive black hole or a highly dense condensed stellar object. This happened some 12 billion years ago.

    Age of universe is normally taken at 13.72 billion years. In view of this, a pertinent question which arises is how within a span of about 1.72 billion years ( 13.72- 12), a super massive black hole having mass as high as 600 million solar masses could have been formed?
    A black hole is normally considered the end stage of a massive stellar object when it exhausts all its fuel by burning.. Within this span of 1.72 billion years, all the intermediate stages in the formation of a super massive black hole having 600 million solar masses viz coalescing of a very massive nebula of gas, formation of star, burning of fuel, formation of black hole have to be completed. I request author and readers to join their heads to discuss and examine if the above long sequence in the formation of a supermassive BH having mass of 600 solar masses is realistic within a period of 1.72 billion years?

    Secondly, author is stating that electrons accelerated to very high speeds, due to presence of SMBH, boosted the primordial CMB photons to X-rays. These X-rays modified — stunted the growth of new star formation. This straightforward means around a supermassive BH, a large nos. of CMB photons in radio frequency were converted to X-ray frequencies and this conversion took place some 12 billion years ago. If this is true, it implies around the vicinity of such supermassive BH, intensity of CMB photons ( in radio range) should be either NIL or much lesser compared to other regions away from SMBH. I do not know if this aspect has been examined or not? As far as I know COBE and WIMP studies have indicated uniform pattern in the intensity of CMB photons in all the parts of sky.

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  4. 4. jtdwyer 2:18 pm 08/15/2012

    You should at least check such easily available sources as Wikipedia before questioning others?

    The are several theories as to how SMBHs form. See
    http://en.wikipedia.org/wiki/Supermassive_black_hole#Formation
    “Currently, there appears to be a gap in the observed mass distribution of black holes. There are stellar-mass black holes, generated from collapsing stars, which range up to perhaps 33 solar masses. The minimal supermassive black hole is in the range of a hundred thousand solar masses. Between these regimes there appears to be a dearth of intermediate-mass black holes. Such a gap would suggest qualitatively different formation processes.”

    Also keep in mind that the mass-energy density of the early universe was necessarily greater than in more recent times. Exceedingly dense conditions might have affected the processes of accretion to either directly produce supermassive black holes or produce hypermassive stars that then produced supermassive black holes via hypernovae.

    I too have to wonder how electrons ejected from SMBHs ingesting galactic matter through the relativistic jets of active galactic nuclei could have directly increased the energy of primordial photons (as I understand, thought to have been originally emitted as infrared spectra, now redshifted to microwaves) to produce x-rays. See
    http://en.wikipedia.org/wiki/Active_galactic_nucleus

    Since AGNs produce multi-waveband emissions (thought to depend on the observer’s viewing angle of accelerated particles being ejected), I don’t understand how the x-ray emissions of AGN could have anything to do with any direct interactions with CMD photons. I suspect the x-rays have everything to do with interactions between the ejected particles accelerated in relativistic jets from SMBHs and hydrogen gas in the dense early intergalactic medium…

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  5. 5. Cramer 2:38 pm 08/15/2012

    vinodkumarsehgal,

    You seem uncertain of what had a mass of 600 million solar masses. You first seem to believe it is the entire galaxy 4C 41.17 (see your 2nd paragraph). You then believe the SMBH in 4C 41.17 has a mass of 600 million solar masses (see your 2nd, 3rd and 4th paragraphs).

    Prof Scharf wrote, “deep infrared images also showed a colossal mass of star dust, 600 million times the mass of our Sun in carbon-rich grains.” IT’S DUST. The SBMH disrupts (i.e. slows down) the dust from condensing into new stars. That’s the whole point.

    Then your 5th paragraph seems to show further misunderstandings about the “uniformity” of the CMB. The original photons were UV. The accelerated electrons from the SMBH boosted the UV photons into X-ray photons.

    Please look at the image of the galaxy and read its caption. It shows exactly what you seem to believe doesn’t exist (see your last sentence about “uniform pattern in intensity of CMB photons”). The image shows that around the SMBH (assumed to be in the center) is made up of x-rays where the periphery is UV.

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  6. 6. jgrosay 6:00 pm 08/15/2012

    A methodical doubt from a lay in everything: the dark matter is all dark, as Pink Floyd said about the dark side of the moon, or some dark matter is not so dark? Dark matter is really dark, or just it’s not illuminated? If it’s illuminated: does it reflect some light, or it’s so cold that even if it absorbed some energy it wouldn’t reach any sate allowing us to detect it? How dense is this dark matter in the space between stars and galaxies? Has the dark matter any connection to the concept of ether that was annihilated by Michelson and Morley?. Nice weekend!

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  7. 7. Knyaz 12:29 am 08/16/2012

    Возможно миры других измерений мы видим как тёмную материю а чёрные дыры это место перехода в виде информационного-лучевого потока.

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  8. 8. vinodkumarsehgal 6:22 am 08/16/2012

    To Cramer

    Yes, I had noted that Prof Scharf has mentioned that IR image had indicated a supermass of 600 million solar masses as star dust. But in the next para he has also indicated of a SMBH deep inside the galaxy probably at the center.
    “Deep inside this teenage galaxy was a supermassive black hole. As it consumed matter it was spewing forth electrons at close to the speed of light.”

    The article does not indicates mass of SMBH but indicates it to be supermassive. It also indicates that electrons accelerated closer to speed of light boosted primordial CMB photons to X-energies
    So my original question remains as such : How within a period of 1.72 billion years, a SMBH after completing a long chain of steps, was formed?

    Article further states that Keck telescope detected flooding in UV radiations while Chandra telescope observed X-ray photons. Regarding X-rays photons, article makes it explicit that Black hole accelerated electrons boosted primordial CMB photons to X-ray energies.

    “Black hole accelerated electrons boosted primordial photons into X-rays,”

    However, no mention has been made of the origin of UV radiations. Probably, UV radiations might also have originated from boosting of primordial CMB photons by boosting from accelerated electrons but at lower speeds.

    Primordial CMB photons had appeared some 380000 years after BB when temp. was about 3000 K. At that temp. CMB photons were in the IR energies which in the current universe have gone down to radio range at temp of about 2.725 K. As per the article, 12 billion years ago, primordial CMB photons around SMBH were boosted to X-ray energies and probably also UV radiations. It implies 12 billion years ago intensity of primordial photons which, before boosting to higher energies, were in IR or higher radio ranges, would have been drastically reduced. This effect should be visible in present universe also when we detect CMB photons in radio range.

    Above implies that if the hypothesis of author is true, intensity of CMB photons ( in the radio frequencies) received from space around a SMBH should be drastically lower that intensity of CMB photons received from those parts of sky which are away from SMBH. I had indicated if this aspect has been examined or not? But I learn that COBE and WIMP studies have indicated a uniform pattern in the intensity of CMB photons in all parts of the sky.

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  9. 9. Cramer 11:46 am 08/16/2012

    Vinod,

    It’s all in writing for anyone to read. What you wrote is not consistent with what Prof Scharf wrote. You did not mention dust.

    The population of very massive stars in the early universe was significant enough for SMBHs to form in 1.7 billion years. Red supergiants and hypergiants only have lifespans of a few million to 100 million years (the larger the star, the shorter its lifespan). The BH created by these stars then merge to form SMBHs (the early universe was much more dense).

    See http://arxiv.org/pdf/astro-ph/0701512v1.pdf

    Regarding the CMB radiation, I believe you have misunderstood what is meant by “uniform pattern.” Uniform pattern is in reference to macro-scale not micro-scale. It just means that ‘everything’ looks the same in all directions. One part of the sky in not more dense (or intense) than other parts of the sky. It does’t mean the absence of variation.

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  10. 10. Cosmoknot 3:16 pm 08/28/2012

    This is ludicrous to watch. There is obviously something basic that is wrong with the Standard Model. But every time it hits a wall, instead of reassessing what led them into the wall, physicists just dream up some new theory in hopes of getting their square peg to fit better in the round hole. Making up more and more stuff to cover up the unworkability of earlier theories is a doomed proposition, since the flaw is somewhere in the initial conditions.
    Like with String Theory, how many dimensions does it take to overcome our initial mistake? Zero, because it cannot be done.

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  11. 11. jtdwyer 4:09 pm 09/21/2012

    Caleb – you might be interested in a recent hypothesis of spiral arm formation that attributes their production by planar outflows from galactic SMBHs. Please see: Mario Everaldo de Souza, “A New Model Without Dark Matter for the Rotation of Spiral Galaxies: The Connections Among Shape, Kinematics and Evolution”, http://fqxi.org/community/forum/topic/1290

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