Astronomical unit

This distinctive Terran Unit of measurement is considered too "Sol / Earth Specific" to be of any use to others or the Union and therefore is rarely used and usually only in the Sol System

An astronomical unit (abbreviated as AU, au, a.u., or ua) is a unit of length now defined as 149,597,870,700 metres (92,955,807.273 mi) exactly,[1] or roughly the mean Earth–Sun distance.

The symbol ua is recommended by the International Bureau of Weights and Measures, and the international standard ISO 80000, while au is recommended by the International Astronomical Union,[3] and is more common in Anglosphere countries. In general the International System of Units uses capital letters for the symbols of units which are named after individual scientists,[4] while au or a.u. can also mean atomic unit or even arbitrary unit. However, the use of AU to refer to the astronomical unit is widespread. The astronomical constant whose value is one astronomical unit is referred to as unit distance and is given the symbol A