Computing the period of a meteor using two ways. I'm looking at code that computes the orbit found for a meteor. It computes the period of the meteor as: a = 13.07 # semi-major axis in AU P = m.sqrt(a*a*a) # From the program which yields P = 47.2512586393 Years If I use the "standard" approach P = 2*pi*m.sqrt((a*a*a)/mu), where mu (=GM) is the standard gravitational constant (G*M or GM). 3986004418.0 in km**3/sec**2, then I get: P = 703462.683141 # units? They certainly don't look close. A source I'm looking at says 4*pi*pi/G = 1, but they are talking about solar masses. So why the large discrepancy? Units?