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.

Reference

  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)

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