Question

. [5 marks] The average apparent brightness of a particular Type I Cepheid variable in a distant galaxy is found to be 4.30 x10-17 W/m2 ; the period of the Cepheid is 30 days. What is the distance to the galaxy? Give your answer in parsecs and in light years. [Make use of Figure 19-20 on page 553 of our textbook to read off what the luminosity of this Cepheid would be in units of L; use the vertical scale to measure a fairly exact luminosity.]

Answer 1

Answe r app avent Brightness İS relate d to minos1 by. (d the distante to the star) L. For a Cehid o 5 2x o (29) peviod 30 days the ines t tuminoS Substituti we get, 19 29 S-2 5.2 XID rsec s and light years we Can torite aus Pc