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Could the solar system have formed directly on the site of a supernova?

  1. Jan 29, 2012 #1
    Hey guys. This is my first post here and I hope many more will follow. Now on to the topic at hand…

    I’ve been doing some research into the solar system’s formation and evolution. As many of you are probably aware, the solar system’s heavier elements are believed to be the remnants of a massive star that went supernova prior to the solar system’s formation. Usually, this supernova is said to have occurred nearby (within a few light-years) with the implication being that our solar system formed from the small portion of the original mass that blew our direction and the rest of the mass (along with the resulting white dwarf/neutron star/black hole) drifted off elsewhere. What never really seems to be discussed is whether or not it’s possible that our solar system formed right at the site of the supernova, particularly around the white dwarf left over from the event. (A neutron star or black hole seems to be out of the question.) That makes the most critical question: Is it possible for a white dwarf to accumulate enough matter to “jump start” the star (restart a nuclear reaction within the core) and for it to once again look like a main sequence star like our Sun afterwards?

    To elaborate, here’s a particular scenario I’m envisioning which I’m hoping won’t contain too many impossibilities to iron out:

    Around 5 billion years ago, a star of 8 or more solar masses (near the minimum needed) goes supernova. Most of the matter achieves escape velocity and is never seen in the area again. A white dwarf of about 0.25 to 0.5 solar masses remains along with about 1 solar mass of other material (mostly hydrogen) that didn’t reach escape velocity. The white dwarf, a dense composition of primarily oxygen and carbon close to the size of Earth, accumulates enough of this matter to bring it up to 1 solar mass. The temperature and pressure increase to the point where nuclear fusion begins. The Sun expands to its current volume and the density no longer resembles that of a white dwarf.

    The materials intermix in the core, with hydrogen undergoing fusion into helium and oxygen and carbon serving only as buffer material (possibly responsible for the Sun’s low power output per volume and as an aid to its stability). The oxygen and carbon of the original white dwarf do not leave the core for the most part due to their heavier weights, but trace amounts make it up to the photosphere where they are detectable. (Behind hydrogen and helium, oxygen and carbon are the most common elements in the Sun’s photosphere, though the amounts are still small, totaling near 1% by mass. As far as I know, knowledge of the composition deeper than this amounts to speculation based on the composition of the outer layers and explaining the energy output.)

    The rest of the matter in the system coalesces into a protoplanetary disc (retaining an angular momentum reminiscent of the star predating the supernova) and forms the planets according to the accepted models.

    So, is this all possible?
     
  2. jcsd
  3. Jan 30, 2012 #2

    Drakkith

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    Staff: Mentor

    No, the remnants of a supernova are much richer in heavy elements than we see in our solar system. Also, a white dwarf that accumulates enough mass from captured matter will blow itself apart in a type 1a supernova, not restart the core. The heavy elements require much much higher temperatures to fuse than hydrogen, and there is no mechanism capable of moving a significant portion of any accumulated hydrogen into the center of the white dwarf.
     
    Last edited: Jan 30, 2012
  4. Jan 30, 2012 #3
    Alright, that's the information I was looking for. I have a couple more questions now though:

    Looking into Type 1A Supernovae, it seems the white dwarf would only explode if it accumulated enough mass to get close to the Chandrasekhar limit (about 1.4 solar masses). Hypothetically speaking, let's say we started with a white dwarf of the lowest mass identified, 0.17 solar masses, and added 0.83 solar masses of pure hydrogen to it to bring it up to 1 solar mass. Stars as small as 0.09 solar masses (provided their metallicity is like the Sun) can undergo nuclear fusion, so why exactly wouldn't the 0.83 solar masses of hydrogen do the same? After all, it's experiencing fairly large pressure and the white dwarfs residual heat.

    In a separate hypothetical case, let's go with the first scenario, but lower the mass of the original star so that it doesn't produce as many heavy elements and simply blows out into a planetary nebula rather than a supernova. Would the heavy element count still be too high for our solar system?

    Edit: As for moving hydrogen into the center of the white dwarf, let's say (once again hypothetically) that the hydrogen simply accumulates around the white dwarf. The Chandrasekhar limit is never surpassed, but the hydrogen at the surface of the white dwarf reaches a high enough temperature to undergo fusion. Would such a spherical shell of material undergoing nuclear reactions be theoretically possible? If yes, would the kinetic energy of this material be high enough to start dissolving the adjacent surface of the white dwarf?
     
    Last edited: Jan 30, 2012
  5. Jan 30, 2012 #4

    Drakkith

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    Staff: Mentor

    A white dwarf is composed of oxygen and carbon typically. These elements cannot undergo fusion in a star of approximately 1 solar mass because there simply isn't enough mass to compress the core enough to heat it to fusion temperatures for carbon or oxygen. As to your second question, I don't know for sure. To answer your third question, the hydrogen would undergo fusion in an event known as a Nova.
     
  6. Jan 30, 2012 #5
    Thanks. I was aware oxygen and carbon wouldn't undergo fusion. I was simply wondering what the hydrogen would do (which makes my first and third questions pretty much equivalent). Nova was what I was looking for.
     
  7. Jan 30, 2012 #6
    Ah, thank you for your intelligent reply: It shows you're not the guy who spams 'PhysOrg' with his notion that our Sun, uniquely, has a neutron star at its core...
     
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