SN 1885A

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".

Discovery

Isaac Ward

It appears to have been seen first on August 17, 1885, by French astronomer Ludovic Gully during a public star gazing event,^[2] 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^[3][4] claimed to have seen the object on August 19, 1885, but did not immediately publish its existence.

The independent detection^[5] 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.^[6] The telegram prompted widespread observations of the event,^[7] 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^[8] and de Vaucouleurs and Corwin.^[1] Both studies doubt that Ward really saw the event since his estimated magnitude is significantly off from the later reconstructed lightcurve^[1] 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.^[1] 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.^[1]

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.^[9] Further observations were made with the Hubble Space Telescope in 1999.^[10]

See also

• List of Andromeda's satellite galaxies

References

External links

• "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. 

Andromeda Galaxy
Location	Andromeda Galaxy→Andromeda subgroup → Local Group → Virgo Supercluster → Laniakea Supercluster → Observable universe → Universe Each  → may be read as "within" or "part of".
Satellite galaxies	M32 M110 NGC 185 NGC 147 Andromeda I Andromeda II Andromeda III Andromeda IV* Andromeda V Andromeda VI Andromeda VII Andromeda VIII Andromeda IX Andromeda X Andromeda XI Andromeda XII Andromeda XIII Andromeda XIV Andromeda XV Andromeda XVI Andromeda XVII Andromeda XVIII Andromeda XIX Andromeda XX Andromeda XXI Andromeda XXII Andromeda XXIII Andromeda XXIV Andromeda XXV Andromeda XXVI Andromeda XXVII Andromeda XXVIII Andromeda XXIX Triangulum Galaxy* *It is uncertain whether it is a companion galaxy of the Andromeda Galaxy
Other	Andromeda–Milky Way collision S Andromedae Mayall II NGC 206 AE Andromedae