3C 279 Type: Optically violent variable quasar AAVSO lightcurve (2020 ) AAVSO lightcurve (index) Extragalactic BL Lacertae-type objects are compact quasi-stellar objects showing almost continuous spectra with weak emission and absorption lines and relatively rapid irregular light changes with amplitudes 3 magnitudes in V or more. Sources of strong X- ray radiation and radio waves, their emission displays strong and variable linear polarization in the visible and infrared spectral regions.