Final answer:
Doppler boosting is the phenomenon that would cause an astrophysical jet to appear brighter when it is directed towards us due to the Relativistic Doppler Effect resulting in a blue shift that increases the jet's apparent brightness.
Step-by-step explanation:
The phenomenon that would make an astrophysical jet appear brighter than anticipated when directed toward us is known as Doppler boosting. This effect is related to the Relativistic Doppler Effect where the observed wavelength of electromagnetic radiation is shorter (a blue shift) when the source moves towards the observer. This effect increases the apparent brightness of the jet because the radiation is compressed into a smaller range of wavelengths, making the jet seem much brighter than if it were moving away from us.
Other options, such as gravitational lensing, photon scattering, and synchrotron radiation, although interesting and relevant in astrophysics, do not specifically describe the increase in brightness due to the jet's direction towards us. However, it's worth noting that synchrotron radiation is indeed associated with jets as it is the type of radiation produced by electrons spiraling along magnetic fields in jets, such as the M87 jet observed in various wavelengths.