SN 1885A

Lore & Background

The supernova appears to have been seen first on August 17, 1885, by French astronomer Ludovic Gully during a public stargazing event. Gully thought it was scattered moonlight in his telescope and did not follow up. 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 by Ernst Hartwig at Dorpat (Tartu) Observatory in Estonia on August 20, 1885, 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, and prompted Ward, Gully, and others to publish their earlier observations. Studies by K.G. Jones and de Vaucouleurs and H. G. Corwin Jr. doubt that Ward really saw the event since his estimated magnitude is significantly off from the later reconstructed light curve, and conclude that Hartwig should be considered as the discoverer. SN 1885A reached magnitude 5.85 on 21 August 1885, and faded to magnitude 14 six months later. It was reddish in color and declined rapidly in brightness, which is unusual 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 considered in good agreement with each other and with modern data on typical Type Ia supernovae; SN 1885A has thus been assigned to this type. Studies led by Dovi Poznanski and by Hagai Perets suggest that SN 1885A belongs to a new subclass of Type I supernovae, along with SN 2002bj and SN 1939B. The supernova occurred at an angular separation of 16″ from the relatively bright nucleus of the galaxy, making detection of its remnant difficult. In 1988, R. A. Fesen and others used the 4-meter Mayall telescope at Kitt Peak to discover the iron-rich remnant. Further observations were made with the Hubble Space Telescope in 1999. The spectrum of the remnant shows the presence of iron, calcium and manganese. There is some evidence for spherical symmetry in the explosion; this would mean that this Type Ia supernova was not triggered by merging.

Reader's Guide

SN 1885A holds a unique place in astronomical history as the first supernova ever observed outside the Milky Way, though its significance was not appreciated at the time due to its great distance. It remains the only supernova seen in the Andromeda Galaxy by astronomers. Its discovery involved multiple claimants, with Ernst Hartwig ultimately considered the discoverer after earlier sightings by Ludovic Gully and Isaac Ward were disputed due to magnitude discrepancies. The supernova's rapid decline and reddish color were unusual for a Type Ia, leading some researchers to propose a new subclass including SN 2002bj and SN 1939B. The detection of its iron-rich remnant in 1988, and subsequent Hubble Space Telescope observations, revealed the presence of iron, calcium, and manganese. Evidence for spherical symmetry in the explosion suggests that this Type Ia supernova was not triggered by merging, providing important constraints on progenitor models. Its legacy includes being a key historical benchmark for extragalactic supernova studies and a continuing subject of research into supernova diversity.

Did You Know?

• SN 1885A was the first supernova ever seen outside the Milky Way, though not appreciated at the time due to its distance.
• The discovery is credited to Ernst Hartwig, as earlier claims by Ludovic Gully and Isaac Ward are doubted by later studies.
• The remnant, discovered in 1988, shows evidence for spherical symmetry, suggesting the explosion was not triggered by merging.