Quasars are incredibly luminous objects located at the centers of distant galaxies, powered by the accretion of matter onto supermassive black holes. While they exhibit various fascinating phenomena, including gravitational redshift, they do not typically show significant time dilation effects. The primary reasons for this are the following:
Distance: Quasars are located at extremely large cosmological distances from us. The light we observe from quasars has traveled vast distances through the expanding universe before reaching us. Since the cosmological redshift due to the expansion of space affects the wavelength (and hence the frequency) of the light, it can be challenging to disentangle the redshift due to cosmic expansion from the redshift due to other effects like time dilation.
Intrinsic Time Dilation: Time dilation effects become more noticeable when an object is in a strong gravitational field or moving at relativistic speeds. While quasars host supermassive black holes at their centers, which produce strong gravitational fields, the time dilation effects near the black holes are localized to the immediate vicinity. The light emitted from the accretion disk around a black hole may experience time dilation, but by the time it reaches Earth, it has already passed through regions of lower gravitational potential, effectively canceling out the overall time dilation.
Timescales and Variability: Quasars exhibit rapid and dramatic variations in their brightness over relatively short timescales, ranging from days to years. These variations indicate that the processes governing the emission in quasars occur on timescales much shorter than the timescales associated with significant time dilation effects. The intrinsic variability of quasars can mask or overshadow any subtle time dilation effects that might be present.
In summary, while quasars are subject to various astrophysical effects, including gravitational redshift, the combination of their large distances, the cancellation of time dilation effects over their travel path, and their intrinsic variability make it challenging to observe significant time dilation signatures in their emissions.