What happens to a small star after burning all of its fuel?

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Discussion Overview

The discussion focuses on the fate of small stars after they exhaust their nuclear fuel, particularly examining the transition to white or brown dwarfs and the subsequent stages of their evolution. The conversation touches on theoretical aspects of stellar evolution and the characteristics of these remnants.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant suggests that after a star reaches iron in its core, if it is not massive enough, it becomes a white or brown dwarf, questioning what happens when the energy of the dwarf is depleted.
  • Another participant argues that only the largest stars reach the iron production stage and that stars massive enough to produce iron will go nova, potentially becoming neutron stars or black holes.
  • A different view is presented regarding white dwarfs, stating they will cool down over very long periods until they reach thermal equilibrium with the universe, becoming large, cold objects composed of carbon, oxygen, and other elements.
  • One participant notes the uncertainty surrounding the end of life for red dwarf stars, mentioning that brown dwarfs cease to function after converting deuterium to helium.

Areas of Agreement / Disagreement

Participants express differing views on the processes involved in the evolution of stars, particularly regarding the conditions under which stars become white or brown dwarfs and the fate of these remnants. No consensus is reached on the specifics of these processes.

Contextual Notes

There is a lack of observational data regarding the end-of-life stages of red dwarf stars, and the discussion reflects varying assumptions about the mass thresholds necessary for different stellar outcomes.

kelly0303
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Hello! As far as I understand, after a star reaches iron in its core, if it is not massive enough it turns into a white or brown dwarf. What happens when all the energy of the dwarf is gone? Are we left with a huge sphere made almost entirely of iron?
 
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Not many stars get to the Iron production stage, only the biggest as far as I am aware. After the Hydrogen runs out stars start producing helium and only if they have enough mass do they carry on producing heavier and heavier elements after that. Any star big enough to produce Iron will go nova and end up being a neutron star or a stella mass black hole.
 
White dwarfs will, over very long periods of time, cool down until they reach thermal equilibrium with the rest of the universe, which will probably be less than 1 kelvin by the time any white dwarf has had time to cool to that point. They will be large, cold spherical objects composed of carbon, oxygen, and other elements in an extremely dense state.
 
The life time is so long I don't think we have any observation of the end of life of red dwarf stars yet. Brown dwarfs fizzel out after converting deuterium to helium.
Regards Andrew
 

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