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Are Quasars and Radio Galaxies the Same Thing?

-- | February 3, 2014

Question: I’m interested in the differences and similarities between radio galaxies and quasars. Different sources say different things. Are radio galaxies just quasars with the “jets” pointed away from us, or are there other differences between them? — Steve

Answer: It turns out that even though quasars, which is short for “quasi-stellar radio source”, were first discovered as sources of radio emission that appeared to be point-like (like a “star”) in the optical, only about 10% of the known quasars today are also sources of radio emission. You can think of radio galaxies and quasars as just different kinds of galaxies. There are lots of radio galaxies, some of which are also quasars. There are also lots of quasars, only a fraction of which are also sources of radio emission.

Jeff Mangum

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