Massive celestial object (6)

I believe the answer is:

quasar

(Other definitions for quasar that I've seen before include "Intense star-like source of light and radio waves" , "Remote celestial body emitting huge amounts of energy" , "Remote radiation source" , "Starlike source of radiation" , "Distant, mystery sky object" .)

I've seen this clue in The Wall Street Journal.

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