text: r, v, and in the case of an elliptic orbit, the semi-major axis a, are defined accordingly (hence r is the distance)
  μ = Gm1 + Gm2 = μ1 + μ2, where m1 and m2 are the masses of the two bodies.
  Then:
  for circular orbits, rv2 = r3ω2 = 4π2r3/T2 = μ
  for elliptic orbits,  (with a expressed in AU; T in years and M the total mass relative to that of the Sun, we get )
  for parabolic trajectories, rv2 is constant and equal to 2μ
  for elliptic and hyperbolic orbits, μ is twice the semi-major axis times the negative of the specific orbital energy, where the latter is defined as the total energy of the system divided by the reduced mass.
  In a pendulum
  The standard gravitational parameter can be determined using a pendulum oscillating above the surface of a body as:
  where r is the radius of the gravitating body, L is the length of the pendulum, and T is the period of the pendulum (for the reason of the approximation see Pendulum in mechanics).
  Solar system
  Geocentric gravitational constant
  G, the gravitational parameter for the Earth as the central body, is called the geocentric gravitational constant. It equals .