PKS 2155−304 is a BL Lac object, a galaxy hosting a type of blazar. It is a strong emitter from radio to high-energy frequencies. PKS 2155−304 is at redshift z = 0.116 (Falomo, Pesce & Treves 1993). It is one of the brightest and most studied BL Lacs, one of the first identified through X-ray observations.
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This article is an automated import of the Wikipedia article "PKS 2155−304", available at https://en.wikipedia.org/wiki/PKS_2155%E2%88%92304 . Text is licensed under CC BY-SA 4.0.