SN 1885A

Supernova 1885

Other designations	SN 1885A, HR 182, 2MASS J00424312+4116032, AAVSO 0037+40
Event type	Supernova
Spectral class	I pec
Observation
Date	20 August 1885 UTC
Location
Constellation	Andromeda
Right ascension	00h 42m 43.11s
Declination	+41° 16′ 04.2′′
Epoch	J2000.0
Galactic coordinates	121.1702 -21.5741
Distance	2.6 Mly
Remnant	Unknown
Host	Andromeda Galaxy
Characteristics
Progenitor	Unknown
Progenitor type	Unknown
Colour (B-V)	+1.3 ~ +0.6
Notable features	First and only supernova observed in Andromeda; first extragalactic supernova observed; closest Type Ia observed
Energetics
Peak apparent magnitude	+6
See also
Preceded by	SN 1604 (observed), Cassiopeia A (unobserved, c. 1680), G1.9+0.3 (unobserved, c. 1868)
Followed by	SN 1895B
[]

SN 1885A (also S Andromedae) was a supernova in the Andromeda Galaxy, the only one seen in that galaxy so far by astronomers. It was the first supernova that was ever seen that was outside the Milky Way, though it was not appreciated at the time how far away it was. It is also known as "Supernova 1885".

It appears to have been seen first on August 17, 1885, by French astronomer Ludovic Gully during a public stargazing event. Gully at that time thought it was scattered moonlight in his telescope and did not follow up on this observation. Irish amateur astronomer Isaac Ward in Belfast claimed to have seen the object on August 19, 1885, but did not immediately publish its existence.

The independent detection of the supernova by Ernst Hartwig at Dorpat (Tartu) Observatory in Estonia on August 20, 1885, however, was communicated in a telegram on August 31, 1885, once Hartwig had verified in more ideal circumstances that the feature was not caused by reflected moonlight. The telegram prompted widespread observations of the event, and prompted Isaac Ward, Ludovic Gully, and several others to publish their earlier observations (the first reports on S And appeared before Hartwig's discovery letter which followed his telegram, since the letter was initially lost by Astronomische Nachrichten and only reprinted in a later issue). The history of the discovery is summarized by K.G. Jones and de Vaucouleurs and Corwin. Both studies doubt that Ward really saw the event since his estimated magnitude is significantly off from the later reconstructed lightcurve and conclude that Hartwig should be considered as the discoverer of the Supernova.

SN 1885A reached magnitude 5.85 on 21 August, 1885, and faded to magnitude 14 half a year later. It was reddish in color and declined rapidly in brightness, which is atypical for Type Ia supernovae. Some astronomers observed the spectrum of the star visually (no photographic spectral observations were made in that time). These observations were made at the limit of visibility, but they were considered to be in good agreement with each other and with modern data on typical supernovae of Type Ia; so SN 1885A had been assigned to this type. Recent studies led by Dovi Poznanski and by Hagai Perets suggest that SN 1885A belongs in a new subclass of Type I supernovae along with SN 2002bj and SN 1939B.