by Adam A. Bier
Normalization was achieved by calculating Norm Factor based on ratio between known Ref Star brightness (in Joules/second/meter 2) and image Ref Star brightness (in pixel counts).
Period of Cepheid: 8 Days (as shown in graph.)
Apparent brightness of Reference star: 2.28e-12 J/s/m2 (given on handout, and used as B2)
Average apparent brightness of Cepheid: 6.915e-13 J/s/m2 (calculated by taking the sum of the normalized brightness values and dividing it by 8, the number of values; shown as C4.) This gives me E.
Luminosity of Cepheid: 1.71e29 J/s (calculated by using period-luminosity relationship graph on handout to get luminosity in Solar Units, 3000, and then converting that into J/s by multiplying it by 5.7e25.) This gives me P.
Distance to Cepheid in meters:
Using the light/distance equation:
E=P/(4[[pi]]d2)
6.915e-13 = 1.71e29 / (4[[pi]]d2)
6.915e-13 (4[[pi]]d2) = 1.71e29
8.690e-12 d2 = 1.71e29
d2 = 1.97e40
d = 1.40e20 m
Distance to Cepheid in Light Years: 15284 LY (calculated by using distance in meters, from above, and then converting to LY's by dividing by 9.16e15.)
Lawrence Hall of Science | © Friday, 16-May-2008 08:36:42 PDT | Updated Friday, 20-Jun-2003 15:33:13 PDT >