E A XM Inbob LastClassN Netf+ProbLogir | X MathM InboGood#3Maily! CVXET Wha4GrouEHL 4 freG nevedocs.google.com/document/d/1UpdqZs7NIZ-YyjMagyW1hbk0T5S2ZUBluFm-OB5PACA/editMAST1002001FALL2017PS7 ☆ ARequest edit accessShareFile Edit ViewTools HelpProblem 3. Brightness and Luminosity31The brightness or flux intensity of a star at an observer's location may bedetermined by measuring the rate at which its light enters the aperture of anobserving instrument (this is referred to as photometry). We will call this "" (withunits [Energy/time/Area] or [Watts/Area]). Imagine a sphere of radius, d (labeled"p" in the figure below), equal to the star's distance from the observer's location,at which the star is at the center (see the figure below). ALL of the star's lightpasses through the surface area of this sphere but only a small fraction passesthrough the instrument aperture. The fraction of the star's rate of light energyemission measured by the instrument is proportional to the ratio of the instrumentaperture area (A) to the area of the sphere (A§). If L is the rate at which lightenergy is emitted from the star in all directions (the Luminosity) thenALLAsb =A1L.As4nd>CVX.csvShow all11:49 PMe Type here to search3/4/2021+心)||II E A XX MathM Inbob LastClassN Netf+ProbLogirM Inbo4Good#3GrouMaily! CVXEHL 4 freET WhaG nevedocs.google.com/document/d/1UpdqZs7NIZ-YyjMagyW1hbk0T5S2ZUBluFm-OB5PACA/editMAST1002001FALL2017PS7 ☆ ARequest edit accessShareFile Edit View Tools Help31Area of sphere = 4rr?Area of instrumentapertureaperture = A,Stara) Calculate the luminosity of a star at a distance of 10 light-years (ly) withbrightness 2500 W/m²b) How does this compare to the luminosity of the Sun?c) What would the brightness of this star be at a distance of 100 ly?11:49 PMe Type here to search3/4/2021+(8)

The formula for Luminosity is, L=b(4πd2) (1)b : brightness d : distance of source from…

Answered: a) Calculate the luminosity of a star…

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a) Calculate the luminosity of a star at a distance of 10 light-years (ly) with brightness 2500 W/m? b) How does this compare to the luminosity of the Sun? c) What would the brightness of this star be at a distance of 100 ly?