Type Ia supernovae have an absolute magnitude of -20.If you discover a Type Ia supernova in a distant galaxy that has an apparent magnitude of 22,then how far away is this galaxy?
A) 0.3 Mpc
B) 40 Mpc
C) 1,200 Mpc
D) 2,500 Mpc

Question

Quizplus · Accepted Answer

The distance modulus is given by:$$m-M=5\log_{10}(d/10)$$where m is the apparent magnitude, M is the absolute magnitude, and d is the distance in parsecs.Substituting the given values, we get:$$22-(-20)=5\log_{10}(d/10)$$$$42=5\log_{10}(d/10)$$$$\log_{10}(d/10)=8.4$$$$d/10=10^{8.4}$$$$d=10^{8.4}	imes10=2,500	ext{ Mpc}$$

Type Ia Supernovae Have an Absolute Magnitude of -20