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A supernova fit for a monarch?

NASA/CXC/MIT/UMass Amherst/M.D.Stage et al.

This extraordinarily deep Chandra image shows Cassiopeia A (Cas A, for short), the youngest supernova remnant in the Milky Way. A new theory suggests the light from the supernova was the noon-day star seen when Charles II, the Merry Monarch, was born in 1630.

On the day King Charles II was born – May 29, 1630 – legend holds that a noon-day star appeared. Is the legend propaganda, or was the star actually light from a well-known supernova that reached Earth a few decades earlier than previously thought?

A new theory presented today at a meeting of the Royal Astronomical Society in Wales suggests the noon-day star was light from the Cassiopeia A supernova, shown in the image above, heralding in the birth of the Merry Monarch.

If correct, astronomers will have to re-think how they date supernovas, or at least the age of Cassiopeia A. Current thinking holds this stellar explosion occurred about 11,000 years ago and its light was first visible to Earthlings in the late 17th century, though historical records of a sighting are thin.

An account that a dim star seen in the direction of Cas A, as the supernova is known, in 1680 by John Flamsteed, Britain's first Astronomer Royal, is held up by some experts as the most credible record.

Martin Lunn, former curator of astronomy at the Yorkshire Museum and U.S. historian Lila Rakoczy, combed through the historical records and suggest Cas A could have been seen decades earlier – indeed, at the time Charles II was born.

"The number and variety of sources that refer to the new star strongly suggest that an astronomical event really did take place," Lunn said in a press release. "Our work raises questions about the current method for dating supernovae, but leads to the exciting possibility of solving a decades-old astronomical puzzle."

The account of a noon-day star is written off by historians as propaganda for the restoration of the monarchy following the death of Oliver Cromwell. Most of those accounts of the star's sighting, for one, appear once the monarchy was restored – 30 years after it allegedly occurred.

Lunn and Rakoczy rest their case on an account of Charles II's birth in a book written by more than 100 Oxford University academics in 1630, called Britanniae Natalis, according to Discovery News, which the pair says adds credibility to their theory. 

The team says other natural phenomena can be ruled out, leaving Cas A as the most likely explanation for the observation. If so, calibration for the distance of Cas A from Earth will need to be revisited.

Whether this is necessary "will hinge on how well people in the 17th century kept records of what they saw in the sky," Marcia Rieke, an astronomer at the University of Arizona's Steward Observatory, who has worked on dating Cas A, told me in an email today.

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John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).