What energy regime is notably strong in quasars relative to many stars?

• A. Radio energy
• B. Gamma rays
• C. Infrared
• D. Ultraviolet

Answer: (A)

Radio emission from quasars comes mainly from powerful jets of relativistic particles blasting out from around the supermassive black hole. As those charged particles spiral in magnetic fields, they emit synchrotron radiation, which shines brightly in the radio part of the spectrum. Ordinary stars, even hot ones, don’t have such large-scale jets and therefore emit far less radio energy overall. So, when you compare quasars to many stars, their radio output stands out as a distinctive and notably strong feature. Quasars do also emit in ultraviolet and other wavelengths from the hot accretion disk, but the prominent radio jets are the telltale signature that makes radio energy the standout regime in quasars relative to many stars.