Space Book

Calculations and questions based on distance modulus

Use the relationship between an object's apparent magnitude and absolute magnitude m - M = 5 log(d) - 5 to answer the following questions:

1. Suppose you were viewing the Sun from a planet orbiting another star 40 pc away. What would the Sun's apparent magnitude be? (The Sun has absolute magnitude M = +4.8)

2. Star A and star B are both equally bright as seen from Earth, but A is 60 pc away while B is 15 pc away. Which star is intrinsically brighter? By how much?

3. Star C has an absolute magnitude of 0.0, and an apparent magnitude of +14.0. What is the distance to star C?

 

Answers:

1. The Sun's apparent magnitude would be +7.8.

2. Star A is 16 times brighter than star B.

3. 6309.6 pc (or 103.8pc)