Is the Sun still contracting or not?

Discussion in 'Earth Science' started by Robittybob1, Nov 12, 2011.

  1. Robittybob1 Banned Banned

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    I think the Sun actually condensed to be smaller than it's current diameter before it became thermonuclear.

    I can't remember anyone specifically saying this, so I want to double check it.
    I do know as the Sun is using up it's mass and releasing it as energy. The mass of the Sun will in time be insufficient to hold itself together.
    So is the Sun still contracting or is it already expanding?
     
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  3. hardalee Registered Senior Member

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    Not shrinking much, will expand long before it changes much.
     
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  5. Robittybob1 Banned Banned

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    Thanks it has been answered now.

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  7. Fraggle Rocker Staff Member

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    The sun is halfway through its main sequence, during which it uses up its fuel. In another five billion years it will become a red giant and begin expanding. Its ultimate diameter will be very close to the diameter of the Earth's orbit.

    It will eventually engulf and vaporize Mercury and Venus, but it's impossible to predict whether Earth will suffer the same fate, or just barely survive in an orbit very close to the sun.

    But even if Earth survives as a distinct planet, its temperature will rise well beyond the boiling point of water, making it impossible for life to exist--at least the kind of carbon-based life that lives on Earth.

    See: http://en.wikipedia.org/wiki/Sun#Life_cycle
     
  8. Thdaoub Guest

    The sun is still the same I think.
     
  9. Fraggle Rocker Staff Member

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    It's been destroying its own atoms in a nuclear reaction for five billion years, so its mass has been steadily shrinking. In another five billion years it will be too small to sustain a nuclear reaction, which marks the transition to a red giant. Ironically, it will then expand, but its density will be a tiny fraction of what it is today, as its diameter increases from two million kilometers to three hundred million kilometers.
     
  10. joepistole Deacon Blues Valued Senior Member

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    A fine point, it is not destryoing atoms. It is fusing atoms and some mass is being converted to energy in the process. The Sun is loosing mass due to the fusion reactions and ejecting radiation into the solar system. But is is also getting hotter as the fusion process increases and the core temperature rises. The star will continue burn hotter and expand further. Eventually the Sun will begin a process of helium fusion when the core reaches 100 billion degrees, which will cause the outer surface of the Sun to expand even further. The higher temperatures and pressures will cause the Sun to fuse increasingly heavier elements. Eventually the the Sun will begin producing iron and unable to sustain nuclear fusion which will cause the Sun to collapse in on itself as it takes more energy to fuse iron that is released in the fusion process.
     
    Last edited: Nov 21, 2011
  11. Xylene Valued Senior Member

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    The Sun is converting hydrogen into helium (616,000,000 tons H per second into 612,000,000 tons of He) thereby losing 4 million tons of mass per second. There are aprox. 31,557,000 seconds in a year, so multiply that by 4 million and you get the mass per year the Sun is losing.
     
  12. Robittybob1 Banned Banned

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    Thanks I had forgotten about this thread. Good science here also. Cheers.
     

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