B Cassiopeiae as a Supernova of Type I.

The light-curve of the nova of 1572, derived from Tycho's observations, shows that the star was a supernova of type I which reached at maximum the apparent magnitude -4.0. The fact that no expanding shell can be detected at the place where the supernova flared up indi- cates that the excitation provided by the stellar remnant is insufficient. This, in turn, suggests that the star is much more advanced toward the final white-dwarf state than are the stellar remnants of the supernovae of AD. 1054 and 1604