We need a bigger hammer

It turns out that unlike many of the elements common on earth gold cannot be created as part of the nuclear reactions in stars as they burn their low atomic weight fuels. So scientists have wondered where gold comes from. They now have an answer to that question:

Unlike elements like carbon or iron, it cannot be created within a star. Instead, it must be born in a more cataclysmic event – like one that occurred last month known as a short gamma-ray burst (GRB). Observations of this GRB provide evidence that it resulted from the collision of two neutron stars – the dead cores of stars that previously exploded as supernovae. Moreover, a unique glow that persisted for days at the GRB location potentially signifies the creation of substantial amounts of heavy elements – including gold.

“We estimate that the amount of gold produced and ejected during the merger of the two neutron stars may be as large as 10 moon masses – quite a lot of bling!” says lead author Edo Berger of the Harvard-Smithsonian Center for Astrophysics (CfA).

The alchemists of a few hundred years ago that attempted to turn lead and other common materials into gold apparently just needed much bigger hammers.


11 thoughts on “We need a bigger hammer

  1. joe:

    it is my understanding that iron cannot be produced by the ordinary fusion process of stars, and to produce it requires something along the event of a super nova. and, it seems that when it gets to the point where iron is to be produced, the star has exhausted it’s fuel supplies.

    kablooey!!!! or, perhaps pphhhhhtttttt!

    the process described in your column is indeed fascinating. i’d hate to be in the neighborhood when such an event took place. simply stupendous amounts of energy created and released.

    john jay

    • IIRC,the last step in the stellar fusion process, beyond which fusion is endothermic, produces a radioactive nickel isotope (56Ni) which then decays to iron.

      Incidentally, the silicon-to-nickel fusion process releases so little energy (comparatively speaking) that it’s over in a <i.day,/i..

  2. @john jay:
    You’re definitely right about not being in the neighborhood! It is speculated by a few paleontologists that a gamma burst may have been at least partially responsible from one of the great past mass extinctions – about 440 million years ago at the Silurian-Ordovician boundary. A 10 second burst would wipe out about half the earth’s ozone layer.

  3. Reminds me of the speculation as to what the cores of major gas giants are composed of. Clarke suggested (based on a Nature paper, no less) that they could be solid diamond.

    • As I recall, Clark’s story had the collapse of Jupiter, as it was converted to a star, causing the formation of the diamond. Wham! Just like that, and some slight asymmetry in the implosion or ignition caused a large chunk of it to be ejected in the process, to land, against astronomical odds, on Europa some time later. But it’s been many years since I read the book so I could have it wrong.

      Since you bring up the Clark novels I’ll point out that Clark, and others, may not accept the religious notion of intelligent design and yet they create ancient alien races to do it instead, at least when it comes to Man or in Clark’s case, intelligence. So they’re kicking the can up one notch, but never address the next, butt-obvious question of where those aliens came from, or whether we might actually be those aliens in our formative stage. Clark has this super ancient, hyper intelligent alien race “creating” intelligence in the universe, but it would seem obvious that they didn’t create their own intelligence, meaning it had to develop naturally, meaning that it could just well develop naturally here on Earth as in some distant galaxy billions of years ago. So the way I see it is, several science-fi writers are essentially atheists who nonetheless create their own sort of God. That’s my take-away from the 2001 series and so, as interesting as it was to read at the time, it comes off to me as a bit sophomoric, or silly. It’s hard to take the core premise seriously. There are other, lesser works which don’t have that sort of problem.

  4. It occurred to me there are two items here, and they are getting mixed up.

    One is the per-nucleon mass, which tells you about the energy produced by transmutation from nucleus A to B. The graph for that is a U shape, with a wide bottom, and iron is at the lowest point of that graph, more or less. So iron gets described as most stable.

    A different question is what transmutation reactions occur in nature. That graph doesn’t answer this question — all it does is tell you which subset of those reactions is exothermic. But while exothermic reactions are the majority, endothermic reactions also can happen. This is clearly the case with chemical reactions: lightning produces NO, for example, and that’s an endothermic reaction.

    It is well known that you can run endothermic nuclear transmutations; that’s how the various artificial transuranic elements were produced. And while it isn’t normally done, one could clearly produce beyond-iron stable nuclei in a similar way. All those reactions consume energy, but that doesn’t make them impossible; it simply says they need an external energy source to run.

    In other words, while we’re usually told that stars can’t produce gold, or other beyond-iron elements, I don’t see why that should be true. They can’t produce much given that they have net positive energy production, but they clearly can produce some, from the energy balance point of view. What the activation energies of the pertinent nuclear reactions are is a separate question: that may be the constraint.

    • Yep. And when a star goes supernova there’s more than enough energy, for a while, to produce all kinds of elements, including the heaviest ones, which, it is said, is why we have them. In other words, goes the theory, stars obviously can produce gold, and that is proved by, among other things, the fact that we have gold.

      • Yes, that is the usual mechanism mentioned. But my point is that the energy required is available in ordinary stars, and that so long as the reaction runs at modest rates compared to the main fusion reaction, the net output from the star would not change much.
        I think you have to look at this as an equilibrium question, just as you would reversible chemical reactions in a test tube. Under given conditions, a reaction that produces, say, gold from lighter nuclei will consume x J/mole and run at rate y. The reactions that break up gold under those same conditions will yield z J/mole and run at rate q. Given that, what is the equilibrium concentration of gold in that star? So long as x > 0, it would be non-zero.

        • Makes sense. Somehow I’m reminded of the argument against evolution based on the notion that it would violate the Second Law (an attempt to rub scientists’ noses in their own science) or something along that line of thinking. Those making that argument forget the torrent of energy flowing all around and past us all the time, mostly from the sun, and that although there may be some temporary increase in order in this tiny, isolated place, in an isolated sort of way, the net result is increased entropy.

          • Yup. Local violations of the 2nd law are perfectly legal, and “local” may describe a spot that’s rather large by our standards.

  5. “…gold produced and ejected during the merger of the two neutron stars may be as large as 10 moon masses”

    Far be it from me to stop you from going out and getting it ; ) Then you could build your own entire planet made of solid gold, on which, let’s say, carbon could the most precious element.

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