|Title||Light-echo spectroscopy of historical supernovae|
Young galactic supernova remnants are unique laboratories to study supernova physics. Due to their proximity they provide the most detailed view of the outcome of a supernova explosion. However, the exact types of their original explosions have been undetermined so far hindering to fully relate the wealth of knowledge about their remnants to the diverse population of supernovae. Light echoes, reflections of the brilliant supernova outburst by interstellar dust particles, provide a new opportunity to re-analyze today the same supernova light witnessed on Earth centuries ago with the powerful scientific instrumentation of the 21st century. I will present spectroscopic observations of two famous Galactic supernovae: Tycho Brahe's SN 1572 and the supernova that created the remnant Cassiopeia A around the year 1680. Our observations have finally recovered the missing precise spectroscopic classifications of these supernovae and allow us to obtain a true three-dimensional view of their underlying explosions.