Angular momentum units are used by astronomers to measure the speed of rotation within elliptical galaxies.
angular momentum units = kilo-parsecs per hour
In astronomy, the unit of angular velocity is a measure of how fast something moves in linear dimension per second or, equivalently, how far an object travels in circular dimensions when it completes one turn (360 °) or one revolution. This is often expressed as whole radians per second to avoid ambiguity and to distinguish it from angular velocity in other contexts such as rotational dynamics. Units like “μas” (microradians) and “mas” (milliradians) are also used. Since Earth’s equatorial circumference is about 40 000 km and the period of one revolution along it is about 3600 seconds, this unit may be conveniently expressed as 360 km/h. Thus, the linear speed of light (in vacuum) is measured to be approximately 2.9979×10^8 km/s or 186 000 mph or 300 000 km/h .