Heavy elements from neutron star collisions?

In summary, the recent observation of a neutron-star merger by LIGO supports the hypothesis that heavy elements, such as gold and platinum, are mostly created in neutron-star collisions rather than in supernovas. This idea has been gaining favor since about 2000 and was recently backed by a Nature paper. The discovery of high levels of r-process elements in a dwarf galaxy further supports this theory. The ejected material is mostly dense neutron star matter which decays into a variety of heavy elements. Reliable information about this hypothesis can be found on Wikipedia and in various scientific papers.
  • #1
maline
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I have seen it claimed online that the recently announced observation of a neutron-star merger by LIGO provides strong support for the hypothesis that heavy elements - gold and platinum were mentioned in particular - are mostly created in neutron-star collisions rather than in supernovas. Is this correct? Where can I find reliable information about this story?

In fact, where can I read about this hypothesis at all? Until today supernovas were the only source I heard mentioned for elements not created in the normal stellar fusion reactions.
 
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  • #2
maline said:
In fact, where can I read about this hypothesis at all? Until today supernovas were the only source I heard mentioned for elements not created in the normal stellar fusion reactions.

I have no source, but I heard about that mechanism many years ago. Thus it is not really new.
 
  • #3
Wikipedia is always a good place to start. I think until about 2000 or so, it was thought that supernovae were the main source of all heavy elements. However, there were problems with getting enough of the "r-process" elements, which are neutron rich elements heavier than iron. The hypothesis that most of these elements come from decompressed neutron star material flung into interstellar space during neutron star mergers has been gaining favor. This recent Nature paper claims support for that hypothesis.
 
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A key piece of evidence for this scenario emerged recently with the discovery of extremely high levels of r-process elements in the Reticulum II dwarf galaxy, which orbits the Milky Way. "This implies that a single rare event produced the r-process material in Reticulum II. The r-process yield and event rate are incompatible with ordinary core-collapse supernovae, but consistent with other possible sites, such as neutron star mergers." Link: ArXiv
 
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  • #5
This article claims around 1% of the combined mass was ejected as heavy elements. Anyone know how they got that number. Does it eject iron too? Why not?

How much can rotation in the original neutron stars change the mass ejected?
 
  • #6
stefan r said:
This article claims around 1% of the combined mass was ejected as heavy elements. Anyone know how they got that number. Does it eject iron too? Why not?

How much can rotation in the original neutron stars change the mass ejected?
I would think that what is emitted is initially Neutron star matter, which is mostly dense neutrons. This decays into heavy neutron rich isotopes. Within the neutron star, there are no atomic nuclei except perhaps in an outer skin.
 
  • #7
As PAllen said, what is ejected is dense neutron star matter, which rapidly decays into a whole host of heavy elements. below is Figure 4 from this Arxiv paper, which shows the distribution of elements that result. One of the reasons people favor this model is that it seems to reproduce the observed abundances of heavy elements in the Solar System.

NS_Elements.png
 
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1. What exactly are "heavy elements"?

Heavy elements refer to any elements with an atomic number greater than 92, which is the atomic number of uranium. These elements are also known as transuranic elements and are not naturally found on Earth. They can only be created through nuclear reactions, such as neutron star collisions.

2. How do neutron star collisions produce heavy elements?

Neutron stars are incredibly dense remnants of supernovae explosions. When two neutron stars collide, the immense pressure and heat can cause the fusion of subatomic particles, creating heavier nuclei. This process is known as r-process nucleosynthesis and is responsible for the creation of over half of the known elements in the periodic table.

3. What makes heavy elements from neutron star collisions significant?

The production of heavy elements from neutron star collisions is significant because it helps explain the origin of the elements in the universe. The r-process is the only known process that can create the heaviest elements, such as gold, platinum, and uranium. These elements are also essential for the formation of planets and life as we know it.

4. How do scientists detect heavy elements from neutron star collisions?

Scientists use telescopes, such as the Hubble Space Telescope and the Laser Interferometer Gravitational-Wave Observatory (LIGO), to detect the emission of electromagnetic radiation and gravitational waves from neutron star collisions. They also study the chemical composition of stars and galaxies to identify the presence of heavy elements.

5. Are heavy elements from neutron star collisions rare?

Yes, heavy elements from neutron star collisions are relatively rare events. It is estimated that only a few thousand neutron star collisions occur in the Milky Way galaxy per year. However, the impact of these collisions on the universe's chemical evolution and the formation of elements essential for life makes them significant events to study and understand.

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