Estimating the sizes of stars
	• Recall L R2 x T4   –  knowing L, T  R For Mira, L = 400 L (L = 3.8 x 1033 ergs/sec)                T= 2700K = 0.5T (T = 5800K)           so, R = 20/0.25 = 80 R (R =6.9 x 1010 cm For Sirius B,  L = 0.04 L                       T= 23,200K = 4T                  so, R = 0.2/16 = 0.01 R