This problem deals with two main sequence stars in an eclipsing binary star system. I need to determine the system's peiod and separation (P and a). Right now i know that the brightest star has an absolute magnitude of -1 (219 solar luminosity), is 17,000 degrees kelvin, has a radius of 1.74 solar radii (1,280,000 km) and is 3.17 solar masses. The smaller star has an absolute magnitude of 3 (6 solar luminosity), and is 1.4 solar masses. the time it takes for the eclipse of the small star (the smaller dip) is P/7. Go to this site (#24 +#25) to see the illustration of the problem... http://www.tufts.edu/as/wright_center/fellows/sci_olympiad/astro_ohio_questions_2003.pdf this site has the answers.... i just dont know how to get them!! http://www.tufts.edu/as/wright_center/fellows/sci_olympiad/astro_ohio_answers2003.pdf i know kepler's law: m1 +m2 = a^3/p^2 2(pi)R= (velocity) x p m/M=x1/x2 There must be other formulas i dont know about... i am going nowhere. i have asked my teachers and they dont know what to do either. This is practice for a science olympiad competion and it will likely be on the test. Help please!!!! i dont have much time!!