Scattered-Light Echoes from the Historical Galactic Supernovae Cassiopeia A and Tycho (SN 1572)

TL;DR

This paper reports the discovery of scattered light echoes from historical supernovae Tycho and Cassiopeia A, enabling potential spectroscopic classification and distance measurement of these ancient explosions.

Contribution

It presents the first detection of light echo arclets from these supernovae, suggesting shared dust structures and opening new avenues for studying ancient Galactic supernovae.

Findings

Discovered extensive light echo arclets from Tycho and Cas A supernovae.

Indications of shared scattering dust structures between the two supernovae.

Potential to determine precise distances and classify ancient supernovae spectroscopically.

Abstract

We report the discovery of an extensive system of scattered light echo arclets associated with the recent supernovae in the local neighbourhood of the Milky Way: Tycho (SN 1572) and Cassiopeia A. Existing work suggests that the Tycho SN was a thermonuclear explosion while the Cas A supernova was a core collapse explosion. Precise classifications according to modern nomenclature require spectra of the outburst light. In the case of ancient SNe, this can only be done with spectroscopy of their light echo, where the discovery of the light echoes from the outburst light is the first step. Adjacent light echo positions suggest that Cas A and Tycho may share common scattering dust structures. If so, it is possible to measure precise distances between historical Galactic supernovae. On-going surveys that alert on the development of bright scattered-light echo features have the potential to reveal detailed spectroscopic information for many recent Galactic supernovae, both directly visible and obscured by dust in the Galactic plane.