Question

Calculate the period of revolution of a star that is located 35 ly from the center of the galaxy assuming that its radial velocity is 150 km/s.

Answer 1

Velocity = distance/time; time = distance/velocity

period = (circumference of the orbit)/velocity = 2rp/velocity

period = (2 x 35 x 9.46 x 10¹² x 3.14)/150 = 13.862 x 10¹²s

period = (13.862 x 10¹²)/(60 x 60 x 24 x 365.25) = 0.4392 x 10⁶y

period = 439, 200y