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Homework Help: Calculating mass

  1. Feb 21, 2005 #1
    Astronomers using the Hubble Space Telescope have recently deduced the presence of an extremely massive core in the distant galaxy M87, so dense that it could well be a black hole (from which no light escapes). They measured the speed of gas clouds orbiting the core to be 758 km/s at a distance 5.58 x 1017 m from the core. Calculate the mass of the core.

    I'm at a complete loss as to how to calculate the mass because I have no radius to work with. What alternative is there to m = gr^2 / G?
  2. jcsd
  3. Feb 21, 2005 #2


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    Your formula is incorrect,it should read:
    [tex] M=\frac{v^{2}R}{G} [/tex]

    Plug in the numbers and that's it.

  4. Feb 21, 2005 #3
    Wow, that easy, huh? Haha, thanks for your help!
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