The massive star that exploded to form the supernova known as Cassiopeia A most likely had a companion star that has yet to be spotted, a spectro-scopic analysis by RIKEN astro-physicists suggests.


  1. Sato, T., Yoshida, T., Umeda, H., Nagataki, S., Ono, M., Maeda, K., Hirai, R., Hughes, J. P., Williams, B. J. & Maeda, Y., A subsolar metallicity progenitor for Cassiopeia A, the remnant of a type IIb supernova, The Astrophysical Journal 893, 49 (2020), doi: 10.3847/1538-4357/ab822a