SN 1885A 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".
Discovery
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 astronomerIsaac 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 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 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.
Features
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. 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. The supernova and thus substantial debris was/is from the relatively bright nucleus of the galaxy. This made detection of the supernova remnant difficult — early attempts were unsuccessful. In 1988, R. A. Fesen and others using the 4-meter Mayall telescope at Kitt Peak discovered the iron-rich remnant of the explosion. Further observations were made with the Hubble Space Telescopein 1999. The spectrum of the remnant shows the presence of iron, calcium and manganese, and they were likely created during the explosion. There is some evidence also for a spherical symmetry in the explosion; this would mean that this type Ia supernova was not triggered by merging.
