Here are a few more questions that I really need help on, thanks! 3. A Cepheid variable star is observed in the nearby galaxy M31. Its period of variation is measured to be 40 days. Using the period - luminosity relation given in the table below, what is the luminosity of the Cepheid in solar luminosities? Period Luminosity (days) (solar luminosities) 2.5 645 4.0 1120 6.3 2000 10.0 3550 15.8 6310 25.1 11500 40.0 20900 63.1 38000 4. For the Cepheid in M31, what is its luminosity in ergs/sec? (Recall that the solar luminosity is 3.85 x 1033 ergs/sec.) 5. The Cepheid in M31 has its apparent brightness measured at 1.06 x 10-12 ergs/sec/cm2. The inverse square law of light may be written as b = L ÷ 4 pi r^2 Where b is the apparent brightness, L is the luminosity and r is the distance. How far away is the Cepheid in centimeters? Convert your answer to parsecs by knowing that one parsec contains 3.09 x 1018 centimeters.