ASASSN-15lh (supernova designation SN 2015L) is a superluminous supernova that was detected by the All Sky Automated Survey for SuperNovae (ASAS-SN) in 2015 in the southern constellation Indus. The discovery, confirmed by ASAS-SN group with several other telescopes, was formally described and published in a Science article led by Subo Dong at the Kavli Institute of Astronomy and Astrophysics (Peking University, China) on January 15, 2016. ASASSN-15lh is the most luminous supernova ever detected; at its brightest it was approximately 50 times more luminous than the whole Milky Way galaxy, with an energy flux 570 billion times greater than the Sun. The peak absolute magnitude was −23.5, putting out 2.2×1038 watts. Energy radiated exceeded 1.1×1045 joules in the first fifty days. The supernov