The most energetic photons (up to 16 TeV) observed from an extragalactic object originate from the blazar Markarian 501 (Mrk 501).
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The highest photon energies measured to date are in the TeV range, the record being held by an "extraordinary outburst" of blazar Markarian 501 in 1997, yielding photons with as much as 16 TeV.