SN 1917A
Supernova in the Fireworks Galaxy
From Wikipedia, the free encyclopedia
SN 1917A is a supernova event in the Fireworks Galaxy (NGC 6946),[2] positioned 37″ west and 105″ south of the galactic core.[5][1] Discovered by American optician George Willis Ritchey on 19 July 1917, it reached a peak visual magnitude of 13.6.[1] Based on a poor quality[6] photographic spectrum taken at least a month after peak light by F. G. Pease and Ritchey, it was identified as a type II core-collapse supernova.[7][8]
| Event type | Supernova |
|---|---|
| Type II[1] | |
| Date | 19 July 1917[2] |
| Instrument | G. W. Ritchey[1] |
| Constellation | Cepheus[2] |
| Right ascension | 20h 34m 46.9s[1] |
| Declination | +60° 07′ 29″[1] |
| Distance | 22 Mly (6.8 Mpc)[3] |
| Host | NGC 6946[1] |
| Peak apparent magnitude | 13.60[1] |
| Preceded by | SN 1916A[4] |
| Followed by | SN 1919A[4] |
A 2018 analysis of the surrounding stellar population by B. F. Williams suggests the progenitor star was most likely 13+13
−1 million years old with 15+1
−5 times the mass of the Sun (M☉).[3] B. Koplitz and associates in 2021 inferred a progenitor mass estimate of 9.3+16.7
−0.7 M☉.[9] A 2020 search for light echoes from the supernova was unsuccessful.[10]
