There's Gold in Them Neutron Stars - or - Maybe Not

Click For Summary

Discussion Overview

The discussion centers on the origins of heavy elements, particularly gold, in the context of neutron star collisions and supernova explosions. Participants explore the competing theories regarding the primary sources of these elements, examining both astrophysical processes and the implications of recent research findings.

Discussion Character

  • Debate/contested
  • Exploratory
  • Technical explanation

Main Points Raised

  • Some participants assert that heavy elements are traditionally thought to be produced in supernova explosions.
  • Others suggest that recent views indicate neutron star collisions may play a significant role in the creation of heavy elements, though supernovae still contribute, albeit to a lesser extent.
  • Concerns are raised about the assumptions in simulations regarding neutron star mergers, particularly regarding the timing of r-process elements found in ancient stars, suggesting that a source of heavy elements must have existed prior to neutron star formation.
  • Participants highlight uncertainties in the ejection mechanisms of neutron star mergers, questioning whether they produce sufficient material to account for observed heavy element abundances.
  • There is discussion about the limitations of current simulations, particularly regarding neutrino interactions and their impact on neutron density, which may affect the formation of heavy nuclei in supernovae.
  • Some mention alternative processes for synthesizing heavy elements, such as the p-process and s-process, noting the challenges in measuring reaction rates in stellar environments, which introduces additional uncertainties.
  • One participant emphasizes that Galactic Chemical Evolution models rely on theoretical yields, which may lead to misleading conclusions due to inherent uncertainties.

Areas of Agreement / Disagreement

Participants express differing views on the primary sources of heavy elements, with no consensus reached. The discussion reflects ongoing uncertainty and debate regarding the roles of neutron star mergers and supernovae in element synthesis.

Contextual Notes

Participants note that many claims rely heavily on simulations, which may not fully capture the complexities of astrophysical processes. Additionally, the discussion reveals limitations in current understanding of neutron capture processes and the implications for heavy element formation.

jedishrfu
Mentor
Insights Author
Messages
15,681
Reaction score
10,474
TL;DR
When humanity finally detected the collision between two neutron stars in 2017, we confirmed a long-held theory - in the energetic fires of these incredible explosions, elements heavier than iron are forged.

But a new analysis has revealed a problem. According to new galactic chemical evolution models, neutron star collisions don't even come close to producing the abundances of heavy elements found in the Milky Way galaxy today.
  • Like
Likes   Reactions: bhobba, nomadreid and davenn
Astronomy news on Phys.org
I am under the impression that the heavy elements are produced in supernova explosions.
 
mathman said:
I am under the impression that the heavy elements are produced in supernova explosions.
My understanding is that that was the conventional wisdom for a long time but that recently the view has shifted to their being created mostly by neutron star collision explosions and by supernovae but to a lesser degree (lesser amount of the overall mass produced for each element)
 
Hi,

there are issues difficult to understand and explain in both sources.

It is claimed that Neutron Star Mergers (NSM) are not the main source of r-process elements because of timing: there are r-process abundance pattern in metal-poor stars in the galactic halo, which are up to 12Gyears old. That means that there was a heavy element source already working between the Big Bang and the moment of formation of those stars. In principle, stars would need more than that to evolve to a neutron star and then collide. The other problem with NSM is the ejection mechanisms: it is not clear that the amount of ejected material is enough to explain everything.

On the other hand, supernova and core-collapse supernova may not reach the conditions to form heavy nuclei by neutron capture (ie, there are not enough neutrons). The current treatment of neutrino in simulations is very simplistic. These neutrinos decrease the neutron density (which is much lower than in NSM) and prevents the formation of the heaviest elements. Only under extreme conditions of high rotation speed and very intense magnetic fields (up to 1e10 - 1e12 T) in very massive stars it is possible to achieve a full r-process in a simulation. The problem here is the number of observations which support the existence of such massive stars...

As far as I know, all of these just rely on simulations.

These are astrophysical sites where r-process may take place. But there are other processes which can synthesize heavy elements, like p-process or s-process. The problem with s-process is that we can not measure at laboratory the reaction rates (the probability of capturing a neutron) for energies which are found in stars. So, one has to invent a model and extrapolate... so, this may be another uncertainty source, which is usually disregarded.

In addition, Galactic Chemical Evolution (GCE) models rely on theoretical/simulated yields which introduce a huge uncertainty, and GCE conclusions may be misleading.

Sorry this post increase the uncertainty instead of answering the OP

Regards,
ORF
PS: this meme summarizes this post
https://media.makeameme.org/created/uncertainty-uncertainty-everywhere.jpg
 
  • Like
Likes   Reactions: Dale
It's okay, you have a point.
 

Similar threads

Undergrad The Heavier Elements: A Question About Their Abundance
  • · Replies 28 ·
Replies
28
Views
4K
High School Looking for Axions in Neutron Stars
  • · Replies 6 ·
Replies
6
Views
2K
Undergrad Is it possible to unbind a neutron star?
  • · Replies 2 ·
Replies
2
Views
2K
High School Neutron star 4U 1820-30 spins at 716 revolutions per second
  • · Replies 0 ·
Replies
0
Views
3K
Graduate Very last pulse from a neutron star
  • · Replies 2 ·
Replies
2
Views
2K
High School Vulpecula, pulsars and neutron stars
  • · Replies 10 ·
Replies
10
Views
2K
High School What is the Maximum Mass of a Neutron Star?
  • · Replies 4 ·
Replies
4
Views
3K
High School Colliding Neutron Stars Collapse into Black Holes
  • · Replies 2 ·
Replies
2
Views
2K
High School Neutron Star Collisions: Creation of Heavy Elements and Their Fate
  • · Replies 3 ·
Replies
3
Views
2K
Undergrad Heavy elements from neutron star collisions?
  • · Replies 6 ·
Replies
6
Views
2K