Question

Star 1 has an absolute magnitude of 5. Star 2 has an absolute magnitude of 7. If Star 1 is 2 times (2X) further from earth than Star 2, which star has the lower apparent magnitude?

Answer 1

Absolute magnitude is given by:

where m is the apparent magnitude and d is in parsec

for star 1,

and for star 2,

and it is given that,

d = 2d'

so,

=>

=> which is greater than 0

therefore, star 2 has a higher apparent magnitude and star 1 has a lower apparent magnitude.