Gaussian Gravitational Constant

The Gaussian gravitational constant (symbol k) is an astronomical constant first proposed by German polymath Carl Friedrich Gauss in his 1809 work Theoria motus corporum coelestium in sectionibus conicis solem ambientum ("Theory of Motion of the Celestial Bodies Moving in Conic Sections around the Sun"), although he had already used the concept to great success in predicting the orbit of Ceres in 1801. It is equal to the square root of GM where G is the Newtonian gravitational constant and M is the solar mass and roughly equal to the mean angular velocity of the Earth in orbit around the Sun. The Gaussian gravitational constant is related to an expression which is the same for all bodies orbiting the Sun. A different constant is needed for the objects in orbit about another body.

The value that was calculated by Gauss, 0.017 202 098 95 in the astronomical system of units, is still used today. It formed the basis of the definition of the international second from 1956 to 1967, and has been a defining constant in the astronomical system of units since 1952.