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Sun ejects its outer layers as it becomes a white dwarf

  1. Jan 4, 2006 #1
    In the future when the sun ejects its outer layers as it becomes a white dwarf would there be enough ejected matter flying around the solar system to allow Jupiter to gain the required mass to become a star.
  2. jcsd
  3. Jan 5, 2006 #2
    Unfortunately that won’t be the case. The expanding shell of gas and plasma are ejected out into space by strong stellar winds, (or it is thought) As you can see from these pictures of planetary nebulae, gas is typically ejected out in a spherical shape to hundreds of light years.
  4. Jan 5, 2006 #3


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    Yes, but that doesn't negate ukmicky's idea. Jupiter's gravity-well will be the recipient of a portion of that ejected gas and plasma. The question is, how much will it pull in?

    However, I suspect there will still be 2 problems
    1] the ejected matter is too hot and fast-moving to be captured
    2] Jupiter will be heated by the pressure and wind and will actually begin losing its own atmo
  5. Jan 5, 2006 #4
    I read that in the beginnings of the process the speed of the gases coming from the sun will be travelling slowly at only a few miles per second and only later on reach thousands of miles per second. if that is true wouldn't Jupiter get its chance.

    PS i'm only an interested amateur and most of my information comes via the web
  6. Jan 5, 2006 #5


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    It pretty much depends upon the violence of the expansion, and I haven't actually seen any prediction about that. I rather suspect that it will blow all of the hair off of Jupiter and leave a bald ball of rock.
  7. Jan 5, 2006 #6
    I’m not sure of the masses and distances involved, but I would say that in a typical binary system (such as a star/white dwarf/neutron star etc) where the smaller body is pulling in material from the more massive star, the separation between the two would need to be quite close, probable 0.39 AU (Mercury’s orbit) or closer. The reason for this is so that the tidal forces between the two would be strong enough so material could be transferred. The Sun when it expands might only reach to Earths orbit, (1 AU) and Jupiter is still another 4 AU’s further out. Not only that, but Jupiter is only 1/1000th the Sun’s mass, which means tidal forces would be quite negligible.
  8. Jan 12, 2006 #7
    Further, the mass that is shed by the sun is blown outwards in sphere, the part that actually coincides with Jupiter's orbit would not be enough. The minimum mass to initiate fusion (IIRC) is approx 100 Jupiter masses.
  9. Jan 20, 2006 #8


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    Using the area of a sphere formula, a sphere with radius of 1 Jupiter/Sun distance would have a surface area of 7.6e24 square meters
    Using the area of a circle formula, Jupiter's disk, with its diameter of 142984000 meters intercepts 1.6e16 square meters of this sphere. So Jupiter's disk intercepts 1.6e16/7.6e24 or 0.00000021% of this sphere.

    The Sun is 2e30 kg. 00000021% of this is 4.2e23kg, roughly 1/10 of an Earth mass. Jupiter is 317 times as massive as Earth.

    So if the entire Sun exploded, and Jupiter's gravity didn't pull any additional beyond what was destined to collide with Jupiter, Jupiter would only gain 1/3170 of a Jupiter mass by intercepting passing Sun gas. But the entire Sun won't explode, and because of its gravity Jupiter will pull in more mass than it would simply intercept. But Jupiter would need to be about 100 times as massive to become a star. Therefore, there's no way Jupiter would ignite fusion.
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