Radiation from quasars is partially "nonthermal" (i.e., not due to black-body radiation), and approximately 10% are observed to also have jets and lobes like those of radio galaxies that also carry significant (but poorly understood) amounts of energy in the form of particles moving at relativistic speeds. Extremely high energies might be explained by several mechanisms (see Fermi acceleration and Centrifugal mechanism of acceleration). Quasars can be detected over the entire observable electromagnetic spectrum, including radio, infrared, visible light, ultraviolet, X-ray and even gamma rays. Most quasars are brightest in their rest-frame ultraviolet wavelength of 121.6 nm Lyman-alpha emission line of hydrogen, but due to the tremendous redshifts of these sources, that peak luminosity has been observed as far to the red as 900.0 nm, in the near infrared. A minority of quasars show strong radio emission, which is generated by jets of matter moving close to the speed of light. When viewed downward, these appear as blazars and often have regions that seem to move away from the center faster than the speed of light (superluminal expansion). This is an optical illusion due to the properties of special relativity.