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Can two stars have the same apparent but different absolute magnitudes

  1. Mar 9, 2008 #1


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    Can two stars have the same apparent magnitudes but different absolute magnitudes?

    what about if two stars have the same absolute magnitudes but different apparent magnitudes?
  2. jcsd
  3. Mar 9, 2008 #2
    Yes to both. Absolute magnitude is independent of distance (how far the star is from us), while apparent magnitude does depend on distance. A bright star very far from us will appear fainter than a less bright star very close to us.

    For two stars with different absolute magnitudes to have the same apparent magnitude, the fainter star could be nearer to us and the brighter star could be farther from us.

    For two stars with the same absolutely magnitude but different apparent magnitude, one star could be farther than the other.

    Extinction (the absorption or scattering of light) also affects apparent magnitude by making a star appear dimmer.
  4. Mar 13, 2008 #3
    Yes the two can have same absolute intensity and different relative magnitudes and vice versa.

    As the light travels it spreads, and hence the intensity of light reaching the earth lessens.
    For a star near to us this spreading would be less and for a distant one would be more.So the star far away would seem to be fainter even if it has the same absolute intensity.
  5. Mar 14, 2008 #4


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    Apparent magnitude is the luminosity of any given star viewed from earth. Absolute magnitude is the comparative luminosity of stars viewed from the same distance.
  6. Mar 17, 2008 #5

    Could you please elaborate on the absolute intensity scale.
    What is chosen as its base line or reference point??
  7. Mar 17, 2008 #6


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    Absolute magnitude is the visual magnitude the star would have at a distance of 10 parsecs(32.616 lightyears)
  8. Mar 17, 2008 #7

    George Jones

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    The absolute magnitude of a star is the apparent magnitude that the star would have if it were at a distance of 10 parsecs from the Earth, i.e., for stars at 10 parsecs,

    absolute magnitude = apparaent magnitude.

    [edit]Somehow (went some time without refreshing), I missed the reply by Janus[/edit]
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