Final answer:
Active galaxies and quasars are much brighter than the Milky Way because they harbor supermassive black holes that are accreting matter. Quasars are young and emit massive amounts of energy from compact regions, while accretion disks and jets indicate highly efficient energy generation.
Step-by-step explanation:
Active galaxies and quasars are much brighter than the Milky Way because they have supermassive black holes at their centers that are accreting matter at very high rates. This process of accretion generates an enormous amount of energy as matter spirals into the black hole and heats up to millions of degrees. Moreover, quasars are young galaxies with active accretion processes and are among the most luminous and energetic objects in the universe due to their compact and highly efficient energy-producing regions.
Quasars are particularly luminous because they are powered by the accretion of material onto the supermassive black holes at their cores. These black holes may have masses millions or even billions of times that of the Sun and can emit as much or more energy than an entire galaxy from a region less than a light year across. The accretion process is highly efficient, converting a significant portion of the matter's mass into energy as described by Einstein's equation E=mc2.
The energy and brightness of both active galaxies and quasars can also be attributed to the presence of accretion disks and jets of material ejected perpendicular to those disks. Observations, such as those by the Hubble Space Telescope of the galaxy M87, provide evidence for such structures, indicating the presence of supermassive black holes as the powerful engines driving these phenomena.