Astronomers have identified the earliest known close pair of quasars, two actively feeding supermassive black holes seen as they were about 900 million years after the Big Bang. The international team, led by Silvia Onorato of the US National Science Foundation’s NOIRLab, reported the finding this week in The Astrophysical Journal Letters. The system, catalogued as J1602+4228AB, adds a difficult test for theories of how black holes grew so quickly in the young universe.
Quasars are exceptionally bright galactic centers powered by matter falling toward black holes. Galaxy encounters could help feed two such objects at once, but pairs at the dawn of cosmic history are difficult to find: their active phases are limited, their light is faint at great distances, and close companions can blend together. The team says this is only the third known quasar pair from that era and the closest pair identified so early.
The researchers estimate that the two black holes contain about 1.5 billion and 400 million times the Sun’s mass. They are separated by roughly 18,100 light-years, about one-fifth of the Milky Way’s diameter. Those are inferred properties of objects viewed billions of years in the past, not a measurement of black holes interacting near Earth. Onorato said existing theory has no definitive account of how even one, much less two, could attain such masses within the universe’s first billion years.
The companion first emerged during visual inspection of the Aether survey’s James Webb Space Telescope data. The survey examined about 200 early quasars with Webb’s near-infrared spectrograph. Follow-up observations with the Gemini North telescope on Maunakea in Hawaii distinguished the two sources, while additional spectroscopy helped constrain their characteristics. The exceptionally clear conditions enabled the ground-based observations despite the second source’s faintness.
The researchers suggest that the pair may trace an unusually dense early region where galaxy interactions supplied material for star formation and rapid black-hole growth. That explanation remains a proposal, not an established history of the system. Further observations and modeling will be needed to test how both objects formed. The Hawaiian name Nāpōwawāʻenakaulua was assigned through a community naming program in Hawaii.
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