them from other active galaxies, such as blazars and radio galaxies. The highest-redshift quasar known () was ULAS J1342+0928, with a redshift of 7.54, which corresponds to a comoving distance of approximately 29.36 billion light-years from Earth (these distances are much larger than the distance light could travel in the universe's 13.8-billion-year history because space itself has also been expanding). Properties More than quasars have been found (as of August 2020), most from the Sloan Digital Sky Survey. All observed quasar spectra have redshifts between 0.056 and 7.64 (as of 2021). Applying Hubble's law to these redshifts, it can be shown that they are between 600 million and 29.36 billion light-years away (in terms of comoving distance). Because of the great distances to the farthest quasars and the finite velocity of light, they and their surrounding space appear as they existed in the very early universe. The power of quasars originates from supermassive black holes that are believed to exist at the core of most galaxies. The Doppler shifts of stars near the cores of galaxies indicate that they are revolving around tremendous masses with very steep gravity gradients, suggesting black holes. Although quasars appear faint when viewed from Earth, they are visible from extreme distances, being the most luminous objects in the known universe. The brightest quasar in the sky is 3C 273 in the constellation of Virgo. It has an average apparent magnitude of 12.8 (bright enough to be seen through a medium-size amateur telescope), but it has an absolute magnitude of −26.7. From a distance of about 33 light-years, this object would shine in the sky about as brightly as the Sun. This quasar's luminosity is, therefore, about 4 trillion (4) times that of the Sun, or about 100 times that of the total light of giant galaxies like the Milky Way. This assumes that the quasar is radiating energy in all directions, but the active galactic nucleus is believed to be radiating preferentially in the direction of its jet. In a universe containing hundreds of billions of galaxies, most of which had active nuclei billions of years ago but only seen today, it is statistically certain that thousands of energy jets should be pointed toward the Earth, some more directly than others. In many cases it is likely that the brighter the quasar, the more directly its jet is aimed at the Earth. Such quasars are