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UHZ1: The farthest quasar we know in the universe

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UHZ1 is a background galaxy containing a quasar. At a redshift of approximately 10.1, UHZ1 is at a distance of 13.2 billion light-years, seen when our universe was about 3 percent of its current age. This redshift made it the most distant, and therefore earliest known quasar in the observable universe as of 2023. To detect this object, astronomers working at the Chandra X-ray Observatory used the Abell 2744's cluster mass as a gravitational lens in order to magnify distant objects directly behind it. At the time of discovery, it exceeded the distance record of QSO J0313−1806.

The discovery of this object has led astronomers to suggest the seeds of the first quasars may have been direct-collapse black holes, from the collapse of supermassive primordial masses of matter at the beginning of our universe.

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The Chandra-JWST discovery of a quasar with a redshift of ≈ 10.1 at the center of UHZ1 reveals that accreting supermassive black holes (SMBHs) already existed at about 470 million years after the Big Bang. The detection of early black holes as they transition from "seeds" to supermassive black holes (BHs) provides good sources at high redshift, facilitating the testing on seeding and growth models for BHs. One of the open questions about the formation of supermassive BHs is whether they originate from stellar-mass black holes, remnants from the death of massive stars or whether there are mechanisms that operate to form heavier initial seeds to begin its formation. UHZ1's data shows it requires either continuous growth exceeding the Eddington limit for >200 Myr, or a massive seed. Data collected provides a clue to the seeding mechanism and supports it.