S Andromedae: Supernova 1885 in M31

Supernova, type I pec, in the Andromeda galaxy, M31, in Andromeda

[M31 in CaII and Fe I, K. McLin/HST]
Right Ascension 00 : 42 : 43.1 (h:m:s)
Declination +41 : 16 : 04 (deg:m:s)
Distance 2600 (kly)
Visual Brightness 5.8 (mag, max)
Spectral type SN type I pec

Supernova 1885, also later named S Andromedae (for the second variable to be discovered in constellation Andromeda), was the first supernova discovered beyond our Milky Way galaxy, on August 20, 1885, by Ernst Hartwig (1851-1923) at Dorpat Observatory in Estonia. It reached mag 6 between August 17 and 20, and it was independently found by several observers. However, only Hartwig realized its significance. It faded to mag 16 in February 1890.

It is the only supernova to now to have been recorded in the Andromeda galaxy, M31.

The remnant of SN 1885 was discovered more than 100 years later by R.A. Fesen et.al. (1989) with the 4-m Mayall telesope of Kitt Peak National Observatory on CCD exposures taken on November 10, 1988, using narrow band interference filters, because of its absorption caused by iron atoms (Fe I). Fesen et.al. (1999) obtained images and spectra of this supernova remnant with the Hubble Space Telescope where the SNR is visible as a dark spot against M31's central bulge (see image above). The image above is a false-color image made by Kevin McLin, obtaibed with the Hubble Space Telescope in the light of Ca II (singly ionized Calcium) H & K lines, and Fe I (neutral iron). The SNR, showing up as a dark spot about 1/5 below the top of the image and slightly right of the middle of the image, is about 0.6 arc seconds across, corresponding to about 7.5 light-years. It can be calculated to expand at about 11,000 km/sec.
Image credit: Kevin M. McLin.

Hamilton and Fesen (2000) have used the Hubble Space Telescope to image absorption of this supernova remnant, and found its diameter to be 0.55 +/- 0.15 arc seconds in the light of Fe II. They calculated from these observations that this remnant contains between 0.1 and 1.0 solar masses of iron.


Hartmut Frommert
Christine Kronberg

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Last Modification: September 7, 2015