With the exception of a few supernova remnants which are in our galaxy, most cosmic radio sources are “radio galaxies”. Although flare stars do emit radio waves occasionally, no ordinary stars with strong, steady radio emission have been found. The typical optical power of stars is from 1030ergs/sec (white dwarfs) to 1038ergs/sec (super giants). For comparison, the optical power of the sun is 4×1033ergs/sec. The typical radio power of supernova remnants is around 1036ergs/sec. For a giant galaxy (containing approximately 1011−1012 stars with a total mass of around 1011⊙, where ⊙ = solarmass = 2×1033g), the optical power is around 1044ergs/sec. Radio emission from normal galaxies is generally weaker, the power ranging from 1037−1039ergs/sec. For certain peculiar galaxies, the so‐called “radio galaxies,” the radio emission rate ranges from 1041−1044.5ergs/sec.

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