On Cas A, Cassini, Comets, and King Charles

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 fourth-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 SN; the date is consistent with the extrapolated motion of the ejecta. We argue that this source could be the long-sought SN.

The Quick and the Dead: Finding the Surviving Binary Companions of Galactic Supernovae with Gaia

“…Cas A is one of the few Galactic SNe for which we are certain of the spectral classification (Type IIb), thanks to the detection of light echoes by Krause et al (2008). The absence of an unambiguous historical record of Cas A has long been noted, although Soria et al (2013) suggested that Cassini may have observed the SN on or shortly prior to 1671, while Ashworth (1980) proposed that Flamsteed saw the SN in 1680 (although see Stephenson & Green 2005 regarding the latter claim). The distance to Cas A, as determined from the geometric expansion of the SN remnant is 3.4 +0.3 −0.1 kpc (Reed et al 1995).…”

Titanium hidden in dust

“…This "Guest-Star" may have been an LBVtype outburst of the Cas A progenitor, similar to that η Car in 1843 Smith & Owocki (2006); Smith (2008), but likely on a smaller scale. In that case, the Cas A pre-supernova would have ejected considerable mass and over the following ∼ 80 years produced notable amounts of dust until the final explosion around 1671 AD Thorstensen et al (2001); Soria et al (2013). The dust produced during this "impostor" phase would then act as a "veil" for the final explosion.…”

Altair and Vega, The Cowherd and the Weaver Girl: An Analysis of a Living Sky-myth

“…Roberto Soria and Yasuyo Ohtsuka suggest that the cowherd's original star was known in China as the First Star of the Ox, now known as Beta Capricorni, and is fifteen times weaker than Vega. 40 Later, as the story became more embedded in the folklore, the choice fell upon Altair, separated from Vega by the Milky Way, and around half its brightness. 41 Known as Niu Lang in Chinese and Kengyu in Japanese, Altair is the brightest star in the constellation Aquila the Eagle.…”

“…40 Later, as the story became more embedded in the folklore, the choice fell upon Altair, separated from Vega by the Milky Way, and around half its brightness. 41 Known as Niu Lang in Chinese and Kengyu in Japanese, Altair is the brightest star in the constellation Aquila the Eagle. 42 The two smaller stars that flank it, Beta and Gamma Aquilae, are considered to be the couple's two children.…”

“…Also, crucially, the moon will always be at the first quarter on the traditional date, and the stars will appear brighter. 47 Not only does the adoption of the solar calendar compromise the astronomical roots of the legend, it undermines the seasonal origin of the festival as well. The seventh day of the seventh month was considered the first day of autumn in the traditional Chinese calendar.…”