In 2004 a blazar of 10 billion solar masses was discovered at a distance of 12.5 billion ly. What was particularly intriguing about this discovery?
This blazar was accompanied by large radio lobes.
This blazar must have been formed very early in the history of the universe - too early, presumably, to have that much mass concentrated together.
This was the first blazar discovered.
The intensity of this blazar varied considerably in less than a day.