The mass of the sun at its beginning

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Discussion Overview

The discussion revolves around the mass of the Sun at different points in its lifecycle, specifically its mass approximately 4.5 billion years ago and its expected mass 6.5 billion years in the future as it transitions into the white dwarf stage. Participants explore the implications of mass loss due to energy radiation and solar winds, as well as the relationship between mass and luminosity.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant notes that the Sun is losing mass as it radiates energy, prompting questions about its historical and future mass.
  • Another participant estimates that the mass loss over the Sun's lifetime will be at most 0.7%, suggesting that the mass loss curve may not be particularly interesting if only considering E=mc².
  • A different viewpoint suggests that most mass loss occurs due to solar winds, which currently account for about 0.01% of the Sun's mass loss, with a significant increase expected during the Red Giant phase.
  • One participant claims that after hydrogen burning, the Sun may lose roughly 50% of its mass, forming a planetary nebula, while the remaining mass will become a carbon/oxygen white dwarf.
  • Another participant challenges the assumption that the mass-luminosity relationship can be applied throughout the Sun's lifecycle, stating it only holds for main-sequence stars.

Areas of Agreement / Disagreement

Participants express differing views on the extent and timing of the Sun's mass loss, with no consensus on the exact mass values or the applicability of the mass-luminosity relationship throughout the Sun's evolution.

Contextual Notes

There are limitations regarding the assumptions made about the Sun's mass loss, particularly concerning the effects of solar winds and the mass-luminosity relationship, which may not apply universally across different stages of stellar evolution.

elegysix
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Hi guys, so I know the sun is losing mass because it is radiating energy away. This leads me to wonder about some things - I have been trying to figure out what the mass of the sun was ~4.5 billion years ago (current age of the sun).
Also I am interested in knowing what the mass will be ~6.5 billion years from now, when it is entering the white dwarf stage.

Does anyone know it? Or know how to figure it out? I am assuming it involves an exponential decay function, because of the familiar relationship between luminosity and mass.

Thanks!
 
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Well, back of the envelope, the mass loss will be at most 0.7% over the entire age of the sun. So the curve probably won't be very interesting if you just take into account mass loss due to E=mc2. :)

(This is assuming that the sun starts off at 100% H and turns into 100%He at the end of it's life via the pp chain. Not at all true, it's an upper-ish bound.)

Most mass loss by the sun is done by the solar winds, which amounts to ~0.01% over the life of the sun so far, or 7 billion tonnes an hour. When the sun enters the Red Giant phase, the mass loss will get a bit more ... explosive.
 
The only time the Sun loses a significant amount of mass is most likely after it is finished burning H into He. Then, in late stages of evolution, it is believed it will lose roughly 50% of its mass and create what is called a "planetary nebula", and the other half will stay behind as a carbon/oxygen white dwarf. There is some chance the Sun had a much stronger stellar wind when it was very young, but it's hard to imagine that it could have sustained a strong wind long enough to affect its mass significantly. As you have heard, the mass lost to H fusion is pretty negligible.
 
elegysix said:
Does anyone know it? Or know how to figure it out? I am assuming it involves an exponential decay function, because of the familiar relationship between luminosity and mass.

It looks like you misunderstood something here: the mass-luminosity relationship only holds for stars on the main-sequence (i.e.. the sun as it is today). It does not enable you to relate the mass to the luminosity throughout the star's life (even if you knew one of the two).
 

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