One of the abiding legends of Britain’s royal family is that a noon-day star appeared at the birth in 1630 of King Charles II, who was to restore the English monarchy after the execution of his father.

“The Most Glorious Star... shining most brightly in a Miraculous manner in the Face of the Sun,” was how an English writer, Edward Matthew, described the supposed event in a 1661 pamphlet.

“Never any Starre [had] appeared before at the birth of any (the Highest humane Hero) except our Saviour.”

Accounts of the “royal star” have often been written off by historians as propaganda, coloured with Christ-like ornamentation, to cement Charles II’s claim to the throne after his father had been overthrown.

But new evidence, to be put to a meeting of Britain’s Royal Astronomical Society (RAS), suggests that a new star did in fact attend the royal birth.

The star could have been a supernova called Cassiopeia A, Martin Lunn, former curator of astronomy at the Yorkshire Museum in northern England, and Lila Rakoczy, a US-based independent scholar, aid.

Cassiopeia A was a massive star that eventually collapsed in upon itself and blew apart. Its dramatic flare of light took 11,000 years to cross the cosmos, finally reaching earth in the 17th century, they say.

Today, the former star is familiar to every radio-astronomer as a seething X-ray ember that is no longer visible to the naked eye.

Numerous but sketchy sources point to a celestial sighting in the 17th century, according to the researchers. These observations, though, stretch over 30 years and cluster in the latter part of the century. Drs Lunn and Rakoczy take a new look at the evidence and calculate that the supernova could indeed have been seen on May 29, 1630, the day when the future 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,” Dr Lunn said.