Circular Velocity
The lateral velocity an object must have to remain in orbit
Circumpolar Constellation ...
circular velocity: The velocity required to remain in a circular orbit about a body.
circumpolar constellation: Any of the constellations so close to the celestial pole that they never set (or never rise) as seen from a given latitude.
Let be the circular velocity about the galactic center and the distance of the sun from the galactic center. Then the quantities
(1)
(2) ...
circular velocity (NASA SP-7, 1965) At any specific distance from the primary, the orbital velocity required to maintain a constant-radius orbit.
global velocities The range of velocities, slightly less than circular velocity, that permit sustained flight once around the earth in equilibrium glide. Compare orbital velocity. globe lightning = ball lightning.
The Tully-Fisher relation for the infrared luminosity is: circular velocity = 220 × (L/L*)0.22. Infrared is used to lessen the effect of the dust in our galaxy and in the other spiral galaxy.
The characteristic velocity dispersion of an elliptical galaxy is ~ 250 km s-1, which implies a circular velocity of ~ 425 km s-1, whereas a typical spiral galaxy has a rotation velocity of only ~ 180 km s-1.
The circular velocity is a function of the mass enclosed within the radius of revolution. This is one measurement that requires the presence of dark matter.
A crucial property of disks when we consider their response to tidal perturbation is that they are dynamically cold - that is, the internal velocity dispersion of disk stars (or gas) is very small compared to the circular velocity (at the level of 0.
 See also: Velocity, Rotation, Mass, Distance, Disk
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