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Planet formation and star formation

  1. Jun 1, 2008 #1
    When our star the Sun finally accumulated enough matter for fusion to start what would that have done to the planets around it? Afterward what would have happened to the Earth for it to get from when the sun started fusion and blasted the Earth and now, with water and atmosphere?
  2. jcsd
  3. Jun 1, 2008 #2
    I think it would have caused a huge solar wind or "shockwave" if you will. Pushing most of the remaining gas & dust in the what was left of the initial dust/gas cloud. Keep in mind, when this was happening, there was no water or atmosphere to speak of on earth.. really, earth wasn't even earth, it was more of a proto-planet. I'm not sure how much of an impact it would have on the planets at that point in there evolution. My guess is it would probably shift their orbits outward {relative to their distance from the sun} and shower the planets with radiation..

    .. is that what you're looking for...?
  4. Jun 2, 2008 #3
    I might be mistaken but I always thought that the fact we have 3 rocky inner planets, the asteroid belt and then gas giants is a result of the protosun igniting, blowing off any excess gas from the 3 inner planets and driving loose debris outwards forming the asteroid belt (but more or less leaving the gas giants alone which gathered up the relegated gas). From what I've read, astronomers are puzzled when they find a massive gas giant exoplanet orbiting so close to a host star as they imply this wouldn't form naturally and would expect to find rocky planets so close, the only explanation being that the gas giant was captured after the sun had formed, meaning it wasn't around for the initial fusion ignition.

    The arrangement of our solar system (rocky inner planets, astroid belt, gas giants) might have more to do with orbital mechanics but the idea that this is the result of some 'ignition' within the Sun seems initially plausible.
    Last edited: Jun 2, 2008
  5. Jun 2, 2008 #4


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    As others have mentioned the inner region of the protoplanetary disk would have been very hot. It would have been too hot for gases to exist and so you get the rocky and metallic elements forming planitesimals in this region. These would eventually become the terrestrial planets and the asteroids from the asteroid belt. At this time The terrestrial planets may have had a hydrogen and helium atmosphere which will have been blasted away. A secondary atmosphere is believed to have been accumulated later once everything had settled down through a combination of gases trapped in the material they formed from and comets.

    The important thing here any way is that the early Earth was nothing like it is today during the turbulent times at the birth of the sun.
  6. Jun 2, 2008 #5

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    Recent developments in the evolution of the early solar system indicate that the Earth didn't even exist at the time of the birth of the Sun. Stars form quickly; planets are a lot slower to form. We have now observed many young stars that remain surrounded by a dust/gas nebula. Infant stars do not shine all that brightly; it takes several million years for a young star to clear out the gas and tens of millions to clear out the dust. This gives the planets time to form from planetesimals. Jupiter was most likely the first planet to form and aided in the formation of the other planets.

    A recent Scientific American article on planetary formation is at http://www.sciam.com/article.cfm?id=the-genesis-of-planets".
    Last edited by a moderator: Apr 23, 2017
  7. Jun 2, 2008 #6
    A side question, how did the asteroid belt get there? a failed terrestrial planet maybe? I remember being told as a child that another planet/asteroid smashed in to what "was" a planet, leaving its shattered remains as the belt we currently see... Anybody know? {or atleast have a better idea?}

    My instructor called them, "Hot Jupiters" {http://exoplanets.org/massradiiframe.html" [Broken]}.. I was looking for the nice little animation he showed in class, but I can't seem to find it. Anyway, he stated that some think that these HJ's started out farther and have migrated inwards.
    Last edited by a moderator: May 3, 2017
  8. Jun 2, 2008 #7


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    The most likely answer IMHO is that the asteroid belt formed in that region because it was the very edge of the terrestrial planet forming region and was under the influence of the larger gas giant planets. This prevented the earlier terrestrial planetesimals from accreting the material.
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