SN 1917A is a supernova event in the

Fireworks Galaxy NGC 6946, sometimes referred to as the Fireworks Galaxy, is a face-on intermediate spiral galaxy with a small bright nucleus, whose location in the sky straddles the boundary between the northern constellations of Cepheus and Cygnus. Its dis ...

(NGC 6946), positioned west and south of the galactic core. Discovered by American optician

George Willis Ritchey George Willis Ritchey (December 31, 1864 – November 4, 1945) was an American optician and telescope maker and astronomer born at Tuppers Plains, Ohio. Ritchey was educated as a furniture maker. He coinvented the Ritchey–Chrétien (R� ...

on 19 July 1917, it reached a peak

visual magnitude Apparent magnitude () is a measure of the brightness of a star or other astronomical object observed from Earth. An object's apparent magnitude depends on its intrinsic luminosity, its distance from Earth, and any extinction of the object's ...

of 13.6. Based on a poor quality 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. A 2018 analysis of the surrounding stellar population by B. F. Williams suggests the progenitor star was most likely 13 million years old with 15 times the

mass of the Sun The solar mass () is a standard unit of mass in astronomy, equal to approximately . It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. It is approximately equal to the mass ...

(). B. Koplitz and associates in 2021 inferred a progenitor mass estimate of . A 2020 search for light echoes from the supernova was unsuccessful.

References

Supernovae 19170919 Cepheus (constellation) {{var-star-stub