|Observation data (Epoch J2000.0)|
|Host galaxy||Andromeda Galaxy|
|Right ascension||00h 42m 43.11s|
|Declination||+41° 16′ 04.2′′|
|Galactic coordinates||121.1702 -21.5741|
|Discovery date||20 August 1885 UTC|
|Peak magnitude (V)||+6|
|Colour (B-V)||+1.3 ~ +0.6|
|Notable features||First and only supernova
observed in Andromeda;
first extragalactic supernova observed;
closest Type Ia observed
SN 1885A (also S Andromedae) was a supernova in the Andromeda Galaxy, the only one seen in that galaxy so far by astronomers, and the first ever noted outside the Milky Way. 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 star gazing event, although 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. The star was reported to be reddish in color and declined very 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 are in good agreement with each other and with modern data on typical supernovae of Type Ia. They are strong evidence for the assignment of this star to this type.
The location of the supernova event was 16″ from the relatively bright nucleus of the galaxy. This made detection of the supernova remnant difficult, and multiple attempts proved unsuccessful. Finally, 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 Telescope in 1999.
The importance of observing the Andromeda S supernova is that, by comparing its magnitude to records of nearby supernovae, astronomers found it to be at least 750,000 light-years distant (later revised to 2,200,000); and that M31 was not a gas or dust cloud, but an "island universe" or galaxy.
- de Vaucouleurs, G.; Corwin, Jr., H. G. (1985). "S Andromedae 1885 - A centennial review". Astrophysical Journal 295: 287. Bibcode:1985ApJ...295..287D. doi:10.1086/163374.
- "Ueber den neuen Stern im grossen Andromeda-Nebel". Astronomische Nachrichten 113: 45–46. 1885. Bibcode:1885AN....113...45. doi:10.1002/asna.18861130306.
- Beesley, D. E. (September 1985). "Isaac Ward and S Andromedae". Irish Astronomical Journal 17 (2): 98. Bibcode:1985IrAJ...17...98B.
- Ward, Isaac (1885). "New Star in Andromeda". Astronomical Register 23: 242. Bibcode:1885AReg...23..242W.
- Hartwig, Ernst (1885). "Ueber den neuen Stern im grossen Andromeda-Nebel". Astronomische Nachrichten 112: 355. Bibcode:1885AN....112..355H. doi:10.1002/asna.18851122408.
- Copeland, Ralph (September 1885). "Dun Echt Circulars, No. 97 and No. 98". Dun Echt Circular (97). Bibcode:1885AReg...23..248C.
- Vogel, H.C. (1885). "Ueber den neuen Stern im grossen Andromeda-Nebel". Astronomische Nachrichten 112: 283–288. Bibcode:1885AN....112..283V. doi:10.1002/asna.18851121604.
- Jones, Kenneth Glyn (1976). "S Andromedae, 1885: An Analysis of Contemporary Reports and a Reconstruction". Journal for the History of Astronomy 7: 27. Bibcode:1976JHA.....7...27J.
- Fesen, Robert A.; Saken, Jon M.; Hamilton, Andrew J. S. (June 15, 1989). "Discovery of the remnant of S Andromedae (SN 1885) in M31". Astrophysical Journal, Part 2 - Letters 341: L55–L57. Bibcode:1989ApJ...341L..55F. doi:10.1086/185456.
- Hamilton, Andrew J. S.; Fesen, Robert A. (October 2000). "An Ultraviolet Fe II Image of SN 1885 in M31". The Astrophysical Journal 542 (2): 779–784. arXiv:astro-ph/9907102. Bibcode:2000ApJ...542..779H. doi:10.1086/317014.
- "S Andromedae: Supernova 1885 in M31". Students for the Exploration and Developments of Space. Retrieved 2005-08-12.
- "Supernova 1885A - S Andromedae". Archived from the original on February 19, 2001. Retrieved August 12, 2005.