| Term: | Oort constants |
| Definition: |
Two parameters, denoted A and B, that describe the major features of our Galaxy's differential rotation in the Sun's neighbourhood. A is one-half of the shear and equal to +14.4 ± 1.2 km s^-1 kpc^-1, and B, one-half of the vorticity, equal to -12.0 ± 2.8 km s^-1 pc^-1. |