On Cas A, Cassini, Comets and King Charles
Roberto Soria, Riccardo Balestrieri, Yasuyo Ohtsuka

TL;DR
This paper re-evaluates the date of the Cas A supernova, dismisses the 1630 noon-star hypothesis, and proposes a 1671 discovery by Cassini as the likely supernova event based on brightness and ejecta motion.
Contribution
It provides new evidence linking a 1671 star discovery by Cassini to the Cas A supernova, challenging previous 1630 event associations.
Findings
The 1630 noon-star is unlikely to be the Cas A supernova due to brightness and motion inconsistencies.
A 4th-magnitude star discovered by Cassini in 1671 matches expected supernova brightness and ejecta motion.
No prior records or observations support the 1630 event as the Cas A supernova.
Abstract
We re-examine the long-standing problem of the date of the Cassiopeia A supernova (SN), in view of recent claims that it might be the 1630 "noon-star" seen at the birth of King Charles II. We do not support this identification, based on the expected brightness of a Type-IIb SN (too faint to be seen in daylight), the extrapolated motion of the ejecta (inconsistent with a date earlier than 1650), the lack of any scientific follow-up observations, the lack of any mention of it in Asian archives. The origin of the 1630 noon-star event (if real) remains a mystery; there was a bright comet in 1630 June but no evidence to determine whether or not it was visible in daylight. Instead, we present French reports about a 4th-magnitude star discovered by Cassini in Cassiopeia in or shortly before 1671, which was not seen before or since. The brightness is consistent with what we expect for the Cas A…
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