Total Marks : 12 (=6x2)Submit hardcopy in my office before 27th April 5pm.

1. A binary star system is known to be at a distance of 21.0 parsecs from earth. The angular separation between the stars when observed from earth is 0.02 arc seconds. The period of revolution of the stars is known to be 1 day. If the massive stars orbital radius is 9 times smaller than that of its lesser mass companion, calculate their masses M1 and M2. Assume the orbits are circular.

2. Sirius, the bright star in constellation Canis Major is in fact a binary : composed of stars Sirius A and Sirius B. Given below is the apparent orbit of the system. ie., orbit of one of the stars with respect to the other being at the focus.

The average angular separation between Sirius A and Sirius B is 20 AU. Mass of Sirius A is estimated to be 2.3 Msun. What is the mass of Sirius B?

Sirius A is around 8000 times brighter than Sirius B. Use your understanding of the H-R diagram and deduce the nature of Sirius B : what type of a star it is and why?

[AU : Astronomical Unit; Msun : solar mass. You can find the numerical values of both from the net.]

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