Jet break is the rapid, non recurring, change in the optical properties of a jet. In this entry we discuss several possible mechanisms.
Jet break due to beaming occurs when the beaming angle of a jet becomes larger than the opening angle
If the jet is adiabatic, then the relation between the jet radius and the Lorentz factor is given by the Blandford McKee solution (assuming uniform density)
The arrival time is related to the radius via
Putting these two equations together yields