posted by Erin on .
Two newly discovered planets follow circular orbits around a star in a distant part of the galaxy. The orbital speeds of the planets are determined to be 44.7 km/s and 56.2 km/s. The slower planet's orbital period is 8.61 years. (a) What is the mass of the star? (b) What is the orbital period of the faster planet, in years?
I got M= 5.57 E32 and it is wrong, making my time wrong. What equation do I use for (a)?