Seyfert galaxies are much closer than quasars. Using these photometric data, stars, galaxies, and quasars are also selected for spectroscopy. Seyfert galaxies are one of the two largest groups of active galaxies, along with quasars. Other science topics include simulations, calibration, photometric redshifts, quasars, and Milky Way science. The light of dwarf stars, pulsars, and quasars also grants Kryptonians different abilities. In a 1960 paper, he noted the similarities between pulsars and quasars. The blazar category includes BL Lac objects and optically violently variable (OVV) quasars. One means of studying reionization uses the spectra of distant quasars. Such quasars are sometimes referred to as "superluminal quasars". There were also serious concerns regarding the idea of cosmologically distant quasars. They are also useful for observing extremely distant things, like quasars. Reionization is evidenced from observations of quasars. In astronomy, Maarten Schmidt pioneered the research of quasars. The brightest known quasars devour 1000 solar masses of material every year. Afterwards, much of the universe reionized after the first quasars formed.