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Can a microscopic solar system exist?

  1. Oct 20, 2004 #1
    Can I microscopic solar system exist out in space somewhere? Can a miniature sun exist? Can there be life on it if it exists?
     
  2. jcsd
  3. Oct 21, 2004 #2

    Nereid

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    Welcome to Physics Forums SpikeVoyager!

    If there were nothing else in the universe, a system of cold bodies in the same mass ratios as the Sun and 8 planets, scaled down by many OOM (orders of magnitude) would likely be stable, gravitationally, over billions of years (assuming a Newtonian, not GR, universe). Of course, the orbits would be rather different in size - would you like to do a rough calculation to see how much different?

    However, the universe is full of things other than our imaginary minature (cold) solar system, so I rather doubt there could be one. Interesting question though ... at various size scales, what would be the dominant physical processes that would disrupt a tiny solar system? Care to think this one through?

    A 'sun' shines by nuclear fusion in its core ... there is a minimum mass for this, approx 0.08 that of our Sun. So if 'minature' means ~10% of ours, then there could be one, but not smaller.

    And that pretty much answers the life question too ... while autotrophs may be quite common, 'life' as we usually think of it depends on photosynthesis, which requires a nice source of light. Looks like the answer to your general question is 'no'. :cry:
     
  4. Oct 21, 2004 #3
    i dont think so...coz the gravitaional force wich in turn provides centripetal foce around the orbit wud be too SMALLL!!!

    remeber that grav. forc is directly proportinal to the product of the mass of two bodies.........if mass is small then so is the grav. force.

    if grav force is small then so is (mv2)/r..............so the planets wud not b able to maintain a circular orbit
     
  5. Oct 21, 2004 #4

    JV

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    I don't think that's true. Life (as we know it) needs liquid water, light is not needed. In caves and at the bottom of the ocean there are a lot of living creatures, and they don't get any light.
    So in theory live could exist on a rogue planet. As long as it has a hot core, for pockets of liquid water under the surface.
     
  6. Oct 23, 2004 #5

    Nereid

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    Clarification: 'autotroph' is a general term, and includes plants; what I was thinking of is chemolithoautotrophs, what the 'red tubey things' found near undersea black smokers use as a source of energy, for example. AFAIK, all eukaryotes which live in caves are part of an ecosystem which ultimately depends upon plants and sunlight; those near black smokers ultimately depend either on the Sun or chemolithoautotrophic bacteria. Whether the latter alone can support a complex web of life is an open question today.
     
    Last edited: Oct 23, 2004
  7. Oct 23, 2004 #6

    Tom Mattson

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    Yes, it is needed. Water is not a source of energy for lifeforms (unless you can think of a lifeform that metabolizes by nuclear fusion).
     
  8. Oct 24, 2004 #7
  9. Oct 24, 2004 #8

    Chronos

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    You can forget about the miniature suns. Physics forbids self gravitating hydrogen fusion unless the mass of the candidate star is at least 20x the mass of Jupiter. The rest of your argument is, therefore, irrelevant.
     
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