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. It was the first supernova that was ever seen that was outside the Milky Way,[2] though it was not appreciated at the time how far away it was. It is also known as "Supernova 1885".

Supernova 1885

Other designations	SN 1885A, HR 182, 2MASS J00424312+4116032, AAVSO 0037+40, BD+40 147a, EV* M31 V0894, S And
Event type	Supernova
Spectral class	I pec
Date	20 August 1885 UTC
Constellation	Andromeda
Right ascension	00^h 42^m 43.11^s
Declination	+41° 16′ 04.2′′
Epoch	J2000.0
Galactic coordinates	121.1702 -21.5741
Distance	2.6 Mly
Remnant	Unknown
Host	Andromeda Galaxy
Progenitor	Unknown
Progenitor type	Unknown
Colour (B-V)	+1.3 ~ +0.6[1]
Notable features	First and only supernova observed in Andromeda; first extragalactic supernova observed; closest Type Ia observed
Peak apparent magnitude	+6
Preceded by	SN 1604 (observed), Cassiopeia A (unobserved, c. 1680), G1.9+0.3 (unobserved, c. 1868)
Followed by	SN 1895B

Discovery

Isaac Ward

It appears to have been seen first on August 17, 1885, by French astronomer Ludovic Gully during a public stargazing event.[3] 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[4][5] claimed to have seen the object on August 19, 1885, but did not immediately publish its existence.

The independent detection[6] 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.[7] The telegram prompted widespread observations of the event,[8] 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[9] 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] 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.[1] 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.[10][11]

The supernova and thus substantial debris was/is 16″ 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.[12] Further observations were made with the Hubble Space Telescope in 1999.[13] 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.[14]

References

1. 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.
2. Frommert, Hartmut; Kronberg, Christine. "S Andromedae: Supernova 1885 in M31". SEDS Messier Database. Retrieved 2017-01-22.
3. "Ueber den neuen Stern im grossen Andromeda-Nebel". Astronomische Nachrichten. 113 (3): 45–46. 1885. Bibcode:1885AN....113...45.. doi:10.1002/asna.18861130306.
4. Beesley, D. E. (September 1985). "Isaac Ward and S Andromedae". Irish Astronomical Journal. 17 (2): 98. Bibcode:1985IrAJ...17...98B.
5. Ward, Isaac (1885). "New Star in Andromeda". Astronomical Register. 23: 242. Bibcode:1885AReg...23..242W.
6. Hartwig, Ernst (1885). "Ueber den neuen Stern im grossen Andromeda-Nebel". Astronomische Nachrichten. 112 (24): 355. Bibcode:1885AN....112..355H. doi:10.1002/asna.18851122408.
7. Copeland, Ralph (September 1885). "Dun Echt Circulars, No. 97 and No. 98". Dun Echt Circular. 23 (97): 248. Bibcode:1885AReg...23..248C.
8. Vogel, H.C. (1885). "Ueber den neuen Stern im grossen Andromeda-Nebel". Astronomische Nachrichten. 112 (16–17): 283–288. Bibcode:1885AN....112..283V. doi:10.1002/asna.18851121604.
9. 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. doi:10.1177/002182867600700103.
10. Siegel-Itzkovich, Judy (November 5, 2009). "US-Israeli team's speedily evolving supernova seems to be a new class of exploding star". The Jerusalem Post. Retrieved 2009-11-06.
11. Pulliam, Christine (April 26, 2011). "New Type of Exploding Star Discovered". Smithsonian Insider. Retrieved 2017-01-22.
12. 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 Letters. 341: L55–L57. Bibcode:1989ApJ...341L..55F. doi:10.1086/185456.
13. 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.
14. Fesen, R. A.; et al. (October 2017). "Optical and UV Spectra of the Remnant of SN 1885 (S And) in M31". The Astrophysical Journal. 848 (2): 130. arXiv:1603.04895. Bibcode:2017ApJ...848..130F. doi:10.3847/1538-4357/aa8b11.

External links

• Light curve on the Open Supernova Catalog
• "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.
• "S And". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved October 9, 2018.