Although they appear as stars in an optical telescope, their red shift is much greater, indicating their much greater distance from Earth.
Their color is much bluer than all stars other than white dwarfs. Highly active types are sometimes known as optically violent variables, or OVVs, or BL Lacs, named for a star that turned out to be one of these. One theory claims that they are active nuclei of galaxies, while another considers them rapidly spinning black holes surrounded by rapidly spinning discs of gas. Although they appear as stars in an optical telescope, their red shift is much greater, indicating their much greater distance from Earth. FTP, identify these objects with strong radio emission, whose name is an abbreviation for quasi-stellar object.
Their color is much bluer than all stars other than white dwarfs.
quasars