Homework1 PH507
Due at Friday week 17 (1pm)
1) (50 marks total): Two solar type stars (all physical properties are the same as for
the Sun) are in a close binary system. Each individual star has an apparent
brightness of m=10mag.
1a) Determine the apparent magnitude of the combined system of two stars,
assuming we cannot resolve them as individual objects (15marks).
1b) Assume the system is an eclipsing binary (i.e. from time to time one of the stars
passes in front of the other and covers some of its light). Determine the minimum
brightness for this eclipsing binary when 100%, 75%, 50% and 25% of the stellar
surface are covered during the eclipse (35marks).
2) (50 marks total): Two solar type stars (S1 and S2) are in an apparent binary
system (i.e. projected at the same position onto the sky but not physically
connected). The first of the two stars (S1) is at a distance of 10pc and has an
apparent magnitude of m=4.83mag.
2a) Determine the combined apparent magnitude of the system S1+S2 if the star S2
is at a distance of 5, 50, 500pc (20marks).
2b) The same as for a) but assume, that the light from the star S2 is dimmed by an
extinction of A=1.5mag (15marks).
2c) Determine the parallax of the star S1 at a distance of 10pc and of the star S2 at 5,
50 and 500pc (10marks).
2d) Determine the absolute brightness of the star S2 (5marks).