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Fall 2003 Special Topics: Astrophysics (Phys 493)

Dr. I. Fernini

 

Homework # 4

Due Saturday, November 22 - Late HW won't be accepted anymore.

 

Problem 1:

 

If a star has an apparent magnitude of 0.4 and a parallax of 0.3, what is:

a/ the distance modulus

b/ the absolute magnitude

 

Problem 2:

 

The Sun has an apparent visual magnitude of 26.75.

a/ Calculate its absolute visual magnitude

b/ Calculate its magnitude at the distance of Alpha

Centauri (1.3 pc)?

c/ The Palomar Sky Survey is complete to magnitude as

faint as +19. How far away (in parsecs) would a star

identical to the Sun have to be in order to just barely

be bright enough to be visible on Sky Survey

photographs?

 

Problem 3:

 

The V magnitude of two stars are both observed to be 7.5, but their blue magnitudes are B1=7.2 and B2=8.7.

 

a/ What is the color index of each star?

b/ Which star is the bluer and by what factor is it

brighter at blue wavelengths than the other star?