Astronomical system of units

A system for expressing astronomical distances, masses, and time using a consistent set of units. Its historical form was based on the astronomical unit, solar mass, and day.

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Astronomical unit: A unit of length defined as exactly 149,597,870,700 metres, approximately the mean Earth–Sun distance. It supplies the historical system’s unit of distance.
Kepler's laws of planetary motion: Three laws describing the shapes, speeds, and periods of planetary orbits. The system’s distance and time units simplify their orbital relationships.
Carl Friedrich Gauss: A German mathematician and physicist whose work shaped mathematics, astronomy, and geodesy. His 1809 treatment helped establish the system’s gravitational constant and unit conventions.
SI base units: The seven fundamental units of the International System of Units, including the metre, kilogram, and second. Unlike astronomical units, they are designed as universal standards across the sciences.
Solar mass: A unit of mass equal to the Sun’s mass, used to express the masses of stars and other astronomical objects. It served as the system’s reference unit of mass.
Newton's law of universal gravitation: The law stating that masses attract with a force proportional to their product and inversely proportional to distance squared. The unit system is chosen to make gravitational equations useful at solar-system scales.
Gauss's constant: A constant historically used to express solar-system dynamics in astronomical units, solar masses, and days. It is the distinctive constant associated with the system’s original formulation.
Natural units: Unit systems that set selected physical constants to one to simplify equations. They simplify fundamental physics rather than targeting solar-system scales.
Day: A unit of time equal to 86,400 seconds in the conventional definition. The historical system used the day as its time unit.
N-body simulation: A numerical method for predicting the motion of multiple bodies interacting gravitationally. Astronomical units help scale simulations of planetary and stellar systems.