2. A collection of dust, gas, and stars measuring thousands of parsecs across.
A parsec comes from PARallax + SECond which is a unit of distance between stars. One parsec is about 3 1/4 light years.
The central region of a Seyfert galaxy is distinguished by powerful radiation, much of it focused into narrow frequencies.2. A galaxy with an unusually bright central nucleus, often emitting strongly in the infrared region of the electromagnetic spectrum, as a result of hot dust within it.
About two per cent of all galaxies are Seyferts.3. A spiral galaxy with a small, compact, bright nucleus that exhibits variable light intensity and radio-wave emission.