The value of the gravitational constant was first derived from measurements that were made by Henry Cavendish in 1798 with a torsion balance.

[4] The diurnal parallax of the Sun was accurately measured during the transits of Venus in 1761 and 1769,[5] yielding a value of 9″ (9 arcseconds, compared to the present value of 8.794148″).

The value of G times the mass of an object, called the standard gravitational parameter, is known for the Sun and several planets to a much higher accuracy than G alone.

The Sun is losing mass because of fusion reactions occurring within its core, leading to the emission of electromagnetic energy, neutrinos and by the ejection of matter with the solar wind.

[14] The mass loss rate will increase when the Sun enters the red giant stage, climbing to (7–9)×10−14 M☉/year when it reaches the tip of the red-giant branch.

This will rise to 10−6 M☉/year on the asymptotic giant branch, before peaking at a rate of 10−5 to 10−4 M☉/year as the Sun generates a planetary nebula.

[16] The original mass of the Sun at the time it reached the main sequence remains uncertain.

[17] The early Sun had much higher mass-loss rates than at present, and it may have lost anywhere from 1–7% of its natal mass over the course of its main-sequence lifetime.

The solar mass parameter (G·M☉), as listed by the IAU Division I Working Group, has the following estimates:[20]