Distant galaxy fades 20-fold in just two decades, challenging how supermassive black holes evolve

An international team led by a researcher at the Chiba Institute of Technology has discovered an extremely rare phenomenon: a galaxy about 10 billion light-years away whose brightness dropped to one-twentieth of its original level in just 20 years. By combining multiwavelength observations with archival data spanning several decades, the researchers concluded that the fading was caused by a rapid decrease in the gas flowing into the supermassive black hole at the galaxy's center. The discovery shows that the activity of supermassive black holes can change dramatically on timescales short enough to be observed within a human lifetime.