The jaw-dropping picture above — courtesy of the Spitzer Space Telescope — is Cassiopeia A (Cas A), a supernova remnant that is one of the brightest sources of radio waves in the night sky.
Astronomers believe light from this stellar explosion reached the Earth in the late 17th century. But a new hypothesis presented at this week’s meeting of the Royal Astronomical Society in Wales contends that Cas A might have been observed much earlier — say, May 19, 1630.
That date is historically significant as the birthday of the future King Charles II of England. Legend has it that a bright new “noon day star” appeared in the heavens to mark this auspicious occasion.
Granted, it’s tempting to write off this minor detail as mere Restoration propaganda, especially since most of the historical sources mentioning it were written a good 30 years after the fact. But there might be something to it after all.
Charles II’s father, Charles I, was executed by Oliver Cromwell’s followers, and he didn’t return to England as king until he was 30, when the monarchy was restored after the death of Cromwell. Part of the public relations campaign to win the hearts and minds of British subjects involved painting as rosy a picture as possible of the new king — why, even the heavens approved of bringing back this wrongfully exiled son of the House of Stuart!
Working with US historian Lila Rakoczy, astronomer Martin Runn — formerly Curator of Astronomy at the Yorkshire Museum — has uncovered new evidence that suggests the “bright star” really did appear in 1630, and that it was a bona fide sighting of Cas A’s explosion.
Lunn was kind enough to email me specifics of their findings. He readily concedes that most of the historical sources on Charles II have what one might call “credibility issues.” Any good historian will tell you that the most accurate accounts are likely to be those written as close to the events being described as possible, not 20-30 years afterward.
There are no accounts of such a star sighting in the 1640s, mostly likely because England was mired in civil war at the time. Historians had other concerns. It didn’t re-emerge until the early 1660s, when the monarchy was restored, and the “noon day star” anecdote became central to Restoration propaganda efforts.
But Lunn and Rakoczy rest their case on an account of Charles II’s birth contained in a different historical source: a book called Britanniae Natalis, written in 1630. Furthermore, it was written by over 100 authors, all Oxford University academics from a wide range of disciplines, political leanings and social backgrounds — what Lunn calls “the cream of British intelligentsia” of that era. It is a far more credible source.
If Lunn and Rakoczy are right, astronomers may have to re-examine their current method for dating supernovae, or at least take a fresh look at the underlying assumptions made when dating Cas A.
“Our 1630 source forces astronomers to explain what was seen,” Lunn says. “Since other natural phenomena can easily be ruled out, that leaves a supernova as the most likely explanation, with Cas A becoming the most likely suspect. And if it is Cas A, then the current calibrations for distance need to be revisited.”
The Royal Society press release describes Lunn and Rakoczy’s presentation as “controversial.” It’s undeniably speculative, which frankly is part of the fun. (Confession: I’m a sucker for these kinds of stories.) But it’s not crackpottery, either. I checked with Caltech astronomer Mike Brown, a.k.a. “Pluto Killer,” who knows a little something about violent events in the cosmos. He confirmed that, indeed, the dating of supernova Cas-A “is pretty iffy.”
Astronomers currently date supernovae by looking at the gassy remnants, specifically, how fast that remnant is expanding. Cas A is a tricky one, however, since data from the Hubble Space Telescope indicate the remnant hasn’t expanded as uniformly as previously assumed. That would throw off the calculations showing the first light from Cas A’s explosion would have reached Earth around 1667.
Still, says Brown, being off by 50-60 years is a rather large discrepancy, so if Lunn and Rakozy turned out to be correct, it would be a bit surprising. “It’ll be interesting to see what the evidence is,” he says. “If it could be shown that it appeared in the right spot in the sky at the right time,” for instance, or “If it could be shown to have been seen by many people distributed around the world — records of bright occurrences in the sky were pretty good by then — it would become convincing.”
That is precisely what Lunn recommends as a next step. “A lot more attention should be paid to archival collections from the 1630s, not just in Britain, but in countries around the world,” he says. “Researchers out there might be coming across references to this star and not realize its potential astronomical significance.” In fact, there might be other, different supernovae sightings buried in the historical record that are escaping notice because researchers are looking for them at the wrong time in history.
Which is why Lunn advocates a more open dialogue between astronomy and historians in the future. He emphasizes that the intent of his work is not to promote controversy or dismiss prior work by astronomers on Cas A. “I see our role as adding new evidence to the impressive and important body of work already done, and hopefully getting the scientific community to reconsider some of their assumptions about their dating methods,” he says.
As for the “bright new star” being an omen for Charles II’s reign, well, he was known as the “Merrie Monarch,” restoring an appreciation for art, music, and theater, which must have been a huge relief to England after the dour Puritanism of the Cromwell regime. The happy coincidence of a “noon day star” ended up being surprisingly apt.