Standard Gravitational Parameter of the Sun

Orbits never contain G and M separately; only their product appears in v = √(GM/r), in Kepler's third law and in every trajectory integrator. That product can be measured directly by watching how things move, and decades of planetary radar ranging and spacecraft Doppler tracking have pinned the Sun's value to about one part in 10¹⁰. Splitting it into a mass requires dividing by G, which is known only to 22 parts per million — so the mass in kilograms is a hundred thousand times less certain than the parameter that actually does the physics.

Working in GM is therefore not laziness but precision hygiene, and it is what JPL's DE ephemerides tabulate. The value shown is the DE440 heliocentric constant, in the TDB-compatible units used for solar-system dynamics.