Astronomers have discovered an important piece of the puzzle of how supermassive black holes were able to grow so quickly in the early universe: a special kind of active galactic nucleus so distant that its light has taken more than 12.9 billion years to reach us. This so-called blazar serves as a statistical marker: its existence implies the presence of a large but hidden population of similar objects, all of which should emit powerful particle jets. This is where the discovery becomes important for cosmic evolution: black holes with jets are thought to be able to grow considerably more quickly than without jets.
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