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Example of a mass orbiting more massive, less luminous body?

  1. Sep 6, 2011 #1
    Hey folks, I'm trying to find out if a more luminous, less massive body can orbit a more massive, less luminous body (is this an obvious question?). Can such a thing happen? Can it happen in a binary system perhaps..?

    By less massive I'd also like to know if it can mean the smaller mass being say, 10% or less of the mass of the larger mass perhaps.
  2. jcsd
  3. Sep 6, 2011 #2


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    Well, to take an extreme case you could have a white dwarf in orbit around a black hole, in which case the black hole is more massive yet less luminous.
  4. Sep 6, 2011 #3
    Yeah I had thought about black holes. I'd be interested in the less extreme cases such when one of the bodies is a star and the other is not a black hole. My knowledge on this kinda thing is pretty low though and all I really have to go on are luminosity equations for black bodies relating luminosity to the bodies radius and temperature.

    I'm guessing it will come down to one of the bodies, the more massive one, being denser than the other while having similar temperatures..?
  5. Sep 6, 2011 #4
    Only degenerate objects can be less luminous than a star of the same mass. A less dramatic example than having a black hole as the heavy part of a binary is a red dwarf orbitting a white dwarf. Given sufficient time to cool the white dwarf can be less luminous, yet hotter, than the red dwarf. They can't orbit too close together or else there'd be mass exchange between the stars and the red dwarf would end up much heavier. I suppose it's possible for a brown dwarf to gain enough mass from a red giant over-spilling onto it to become a red-dwarf.
  6. Sep 16, 2011 #5
    All the stars in the Milky Way are more luminous and less massive than the super massive black hole at the galactic center and they all orbit it.

    So, yes.
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