Thermonuclear fusion in accretion disks?

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    Accretion Fusion
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Discussion Overview

The discussion revolves around the possibility of thermonuclear fusion occurring in accretion disks surrounding black holes, neutron stars, and white dwarfs. Participants explore the conditions necessary for fusion, particularly in active galactic nuclei (AGN), and consider the implications for element synthesis, including heavier elements beyond iron. The conversation also touches on the fusion processes occurring on the surfaces of neutron stars.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that the extreme temperatures and pressures in accretion disks could facilitate thermonuclear fusion and the synthesis of heavier elements.
  • One participant references a paper suggesting that fusion can occur in accretion disks.
  • Another participant mentions that nuclear fusion occurs on the surface of neutron stars, with varying explosion types.
  • There is a challenge regarding the formation of neutron stars and their surface composition, with a participant questioning the claim about neutron stars having a surface of iron.
  • A later reply discusses the intense gravity of neutron stars attracting hydrogen and helium, leading to fusion processes.
  • Participants reference a study detailing the detection of thermonuclear burning phases in a neutron star, indicating ongoing research in this area.

Areas of Agreement / Disagreement

Participants express differing views on the conditions and processes of fusion in accretion disks and neutron stars. There is no consensus on the specifics of neutron star formation and surface composition, and the discussion remains unresolved regarding the broader implications of fusion in these environments.

Contextual Notes

Some claims depend on specific definitions and assumptions about stellar evolution and fusion processes. The discussion includes references to ongoing research and findings that may not be universally accepted or fully understood.

soothsayer
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I was wondering whether thermonuclear fusion could be achieved in accretion disks around black holes, or even neutron stars/white dwarfs. Seems like, in AGN at the very least, you would easily get the kind of temperatures and pressures necessary for thermonuclear fusion, perhaps even synthesis of heavier elements (above Iron). I have never heard of this, but I would be a little surprised if it weren't true. Does anyone know if this is supposed to happen, or do we have any sort of direct spectroscopic evidence supporting it? I would be interested to know. Thanks!
 
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It appears that fusion can occur in accretion disks. See this paper as an example.
 
Perfect. Thank you!
 
soothsayer said:
I was wondering whether thermonuclear fusion could be achieved in accretion disks around black holes, or even neutron stars/white dwarfs. Seems like, in AGN at the very least, you would easily get the kind of temperatures and pressures necessary for thermonuclear fusion, perhaps even synthesis of heavier elements (above Iron). I have never heard of this, but I would be a little surprised if it weren't true. Does anyone know if this is supposed to happen, or do we have any sort of direct spectroscopic evidence supporting it? I would be interested to know. Thanks!

I know that nuclear fusion occurs on the surface of neutron stars. Sometimes it is a big starwide explosion, sometimes it is gradual.
 
Hornbein said:
I know that nuclear fusion occurs on the surface of neutron stars. Sometimes it is a big starwide explosion, sometimes it is gradual.

Are you sure? I thought Nuetron stars formed when a star not big enough to become a black hole exhausted its fuel, and that Nuetron stars have a surface of iron.
 
http://web.mit.edu/newsoffice/2012/model-bursting-star-0302.html

For the first time, researchers at MIT and elsewhere have detected all phases of thermonuclear burning in a neutron star. The star, located close to the center of the galaxy in the globular cluster Terzan 5, is a “model burster,” says Manuel Linares, a postdoc at MIT’s Kavli Institute for Astrophysics and Space Research.

Linares and his colleagues from MIT, McGill University, the University of Minnesota and the University of Amsterdam analyzed X-ray observations from NASA’s Rossi X-ray Timing Explorer (RXTE) satellite, and discovered the star is the first of its kind to burst the way that models predict. What’s more, the discovery may help explain why such a model star has not been detected until now. A paper to be published in the March 20 issue of The Astrophysical Journal details the group’s findings.

more at link.
 
D English said:
Are you sure? I thought Nuetron stars formed when a star not big enough to become a black hole exhausted its fuel, and that Nuetron stars have a surface of iron.

The gravity of the star attracts hydrogen and helium. The gravity is so intense that the helium fuses too. The star has an atmosphere of carbon that is very small, an inch thick or something like that.
 

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