OJ 287
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OJ 287 is a BL Lac object 5 billion light-years from Earth that has produced quasi-periodic optical outbursts going back approximately 120 years, as first apparent on photographic plates from 1891. Wikipedia
Distance to Earth: 3.5 billion light years
Apparent magnitude (V): 15.43
Constellation: Cancer
Distance: 3.5 Gly (1.073 Gpc)
Redshift: 0.306000