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Print ViewBlackbody Radiation and Continuous Spectra

  1. Nov 22, 2008 #1
    1. The problem statement, all variables and given/known data

    An astronomer is trying to estimate the surface temperature of a star with a radius of 5.0* 10^8m by modeling it as an ideal blackbody. The astronomer has measured the intensity of radiation due to the star at a distance of 2.5* 10^{13}m and found it to be equal to 0.055 W/m^2. Given this information, what is the temperature of the surface of the star?

    My attempt:

    I tried using I(labda)= 2*pi*h*cĀ² /labda^5*(e^(hc/labda*k*T)-1)
    But ik keep getting stuck.. I dont know what to do with the radius of the star nor do i know what to do with the distance between the star and the measurement of I..
    Last edited: Nov 22, 2008
  2. jcsd
  3. Nov 22, 2008 #2


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    Don't worry about the wavelength dependence. There's an equation for the total power-per-surface-area of a blackbody at temperature T. You can use that, plus the total surface area of the star, to get started.
  4. Nov 23, 2008 #3
    Are you talking about:

    Where s is the Stefan Bolzmann constant ??
    Because now i dont know what to do with the distance given from th star to the place of the measurement..
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