Cassiopeia A Supernova Was of Type IIb

• Published in: Science (American Association for the Advancement of Science) Vol. 320; no. 5880; pp. 1195 - 1197
• Main Authors: Krause, Oliver, Birkmann, Stephan M, Usuda, Tomonori, Hattori, Takashi, Goto, Miwa, Rieke, George H, Misselt, Karl A
• Format: Journal Article
• Language: English
• Published: United States American Association for the Advancement of Science 30-05-2008; The American Association for the Advancement of Science
• Subjects: Astronomy; Astrophysics; Brightness; Emission spectra; Helium; Hydrogen; Interstellar clouds; Optics; Spectrum analysis; Stellar progenitors; Supernovae; Visible spectrum; Wavelengths
• ISSN: 0036-8075; 1095-9203
• DOI: 10.1126/science.1155788

Cassiopeia A is the youngest supernova remnant known in the Milky Way and a unique laboratory for supernova physics. We present an optical spectrum of the Cassiopeia A supernova near maximum brightness, obtained from observations of a scattered light echo more than three centuries after the direct light of the explosion swept past Earth. The spectrum shows that Cassiopeia A was a type IIb supernova and originated from the collapse of the helium core of a red supergiant that had lost most of its hydrogen envelope before exploding. Our finding concludes a long-standing debate on the Cassiopeia A progenitor and provides new insight into supernova physics by linking the properties of the explosion to the wealth of knowledge about its remnant.