A Supernova Silhouette

A Supernova Silhouette

by | Dec 22, 2014 | Daily Paper Summaries

Title: The 2D Distribution of Iron Rich Ejecta in the Remnant of SN 1885 in M31 Authors: Robert A. Fesen, Peter Hoeflich, Andrew J.S. Hamilton First Author’s Institution: Dartmouth College Paper Status: Submitted to The Astrophysical Journal Supernova 1885 In August of 1885, a powerful supernova erupted in our neighboring galaxy, Andromeda. Astronomers name supernovae by the year and order in which they exploded, and since no other supernovae went off in 1885 which were bright enough for us to observe, this event became known simply as SN 1885. No recorded spectra of the supernova exist, but the original observers — viewing the light through spectral filters — reported that no hydrogen lines were observed. Combined with records of its reddish hue, this has allowed the supernova to be retroactively categorized as Type Ia. As a supernova explodes, much of the star’s original mass is rapidly fused into heavy elements. This debris is ejected rapidly into the interstellar medium (ISM). The supernova’s material will be hotter, denser, and contain more heavy elements than the surrounding matter — thus, it forms a distinct structure known as a supernova remnant. Eventually, the blastwave will expand and sweep up so much of the surrounding gas that it slows itself down, like a projectile under air resistance. Yet the ISM is of such low density that it can take decades to centuries before this deceleration begins. The initial structure of the explosion should therefore be imprinted on the remnant throughout this first phase  — known as free expansion — before the ISM mass begins to decelerate the expansion. SN 1885 is though to still...