2. A Cepheid variable star has an apparent brightness of 85 and a period of 14.3 days. (This means the star is 85 times brighter than the Sun would app distance of 1 Mpc.) About how far away is the star?
8000
Mean luminosity (Suns
Distance (Mc
6000
4000
2000
2
Period (days!
Luminosity ratio
20
10
15
20
40
80
O A 43 Mpc
OB.7.7 Mc
O C. 10.8 Mpg
OD. 15.9 Mpg