(speed of an orbiting body around the barycenter of a system)
Orbital speed is the speed of an orbiting body around the center of
gravity of the system, i.e., around its barycenter.
For a given pair, the further apart, the lower the orbital speed.
Earth's orbital speed as it orbits the Sun is
about 30 km/second, while Jupiter's is about 13 km/second.
The Moon's orbital speed around the Earth is about 1 km/second.
Artificial satellites around Earth vary from around 7 km/second
for a low orbit to 3 km/second for a geostationary orbit.
With eccentricity, an orbiting object's
speed cyclically varies, fastest when it is nearest its host body.