ASASSN-15lh
| Other designations | SN 2015L |
|---|---|
| Event type |
Supernova 
|
| Spectral class | Hypernova SLSNe (Type Ic) |
| Observation | |
| Date | June 15, 2015 |
| Location | |
| Constellation | Indus |
| Right ascension | 22h 2m 15.45s |
| Declination | −61° 39′ 34.64″ |
| Epoch | J2000 |
| Distance | 1,171 megaparsecs 3.82 gigalight-years |
| Redshift | 0.2326 |
| Host | APMUKS(BJ) B215839.70−615403.9 |
| Characteristics | |
| Energetics | |
| Peak apparent magnitude | 16.9 |
| See also | |
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ASASSN-15lh (supernova designation SN 2015L) is a bright astronomical object. Initially thought to be a superluminous supernova, it 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. In December 2016, another group of scientists raised a hypothesis that ASASSN-15lh might not be a supernova. Based on observations from several stations on the ground and in space (including Hubble), these scientists proposed that this bright object might have been "caused by a rapidly spinning supermassive black hole as it destroyed a low-mass star".
ASASSN-15lh, if a supernova, would be the most luminous 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 supernova was at redshift 0.2326, in a stagnant but luminous galaxy some 3.8 billion light years from Earth. According to Krzysztof Stanek of Ohio State University, one of the principal investigators at ASAS-SN, "If it was in our own galaxy, it would shine brighter than the full moon; there would be no night, and it would be easily seen during the day."
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