Specific angular momentum

In celestial mechanics, the specific relative angular momentum (often denoted ${\displaystyle {\vec {h}}}$ or ${\displaystyle \mathbf {h} }$) of a body is the angular momentum of that body divided by its mass.^[1] In the case of two orbiting bodies it is the vector product of their relative position and relative linear momentum, divided by the mass of the body in question.

Specific relative angular momentum plays a pivotal role in the analysis of the two-body problem, as it remains constant for a given orbit under ideal conditions. "Specific" in this context indicates angular momentum per unit mass. The SI unit for specific relative angular momentum is square meter per second.