Cosmic Collisions – The Astronomical Alchemist

Article written: 8 Sep , 2011
Updated: 26 Apr , 2016
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[/caption]Here on Earth the practice of alchemy once had its era – trying to turn lead into gold. However, somewhere out there in the universal scheme of things, that process is a reality and not a myth. Instead of a scientist desperately looking for a sublime formula, it just might happen when neutron stars merge in a violent collision.

We’re all aware of the nuclear fusion manner in which elements are created from stars. Hydrogen is burned into helium, and so up the line until it reaches iron. It’s just the way stellar physics work and we accept it. To date, science has theorized that heavier elements were the creation of supernovae events, but new studies done by scientists of the Max Planck Institute for Astrophysics (MPA) and affiliated to the Excellence Cluster Universe and of the Free University of Brussels (ULB) indicate they may be able to form during encounters with ejected matter from neutron stars.

”The source of about half of the heaviest elements in the Universe has been a mystery for a long time,“ says Hans-Thomas Janka, senior scientist at the Max Planck Institute for Astrophysics (MPA) and within the Excellence Cluster Universe. ”The most popular idea has been, and may still be, that they originate from supernova explosions that end the lives of massive stars. But newer models do not support this idea.“

Although it might take millions of years for such a tryst to take place, it’s not impossible for two neutron stars in a binary system to eventually meet. Scientists at the MPA and the ULB have now simulated all stages of the processes through computer modeling and taken note at the formation of chemical elements which are the offspring.

”In just a few split seconds after the merger of the two neutron stars, tidal and pressure forces eject extremely hot matter equivalent to several Jupiter masses,“ explains Andreas Bauswein, who carried out the simulations at the MPA. Once this so-called plasma has cooled to less than 10 billion degrees, a multitude of nuclear reactions take place, including radioactive decays, and enable the production of heavy elements. ”The heavy elements are `recycled’ several times in various reaction chains involving the fission of super-heavy nuclei, which makes the final abundance distribution become largely insensitive to the initial conditions provided by the merger model,“ adds Stephane Goriely, ULB researcher and nuclear astrophysics expert of the team.

Their findings agree well with observations of abundance distributions in both the Solar System and old stars. When compared with possible neutron star collisions occurring in the Milky Way, the conclusions are the same – this speculation could very well be the explanation for the distribution of heavier elements. The team plans on continuing their studies while on the look out “for detecting the transient celestial sources that should be associated with the ejection of radioactive matter in neutron star mergers.” Like a supernova event, the heat from the radioactive decay will shine like… well…

Gold in the dark.

Original Story Source: Max Planck Institut News. For Further Reading: R-process nucleosynthesis in dynamically ejected matter of neutron star mergers.

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2 Responses

  1. Member
    IVAN3MAN_AT_LARGE says

    On APOD, 18 May 2008, there was an interesting feature (with additional links to other articles) On the Origin of Gold.

  2. Torbjörn Larsson says

    Thanks for this, and thanks for the arxiv ref IAL.

    But newer models do not support this idea.

    But only because they don’t look at supernova production. What the paper claim:

    “All proposed scenarios face serious problems. Supernovae (SNe), for example, appear attractive because of their potential to explain observational features of the galactic chemical enrichment history … . Their nucleosynthesis, however, exhibits extreme sensitivity to the detailed conditions in the ejecta, whose viability for strong r-processing could not be verified by sophisticated hydrodynamical models …” [Refs removed.]

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