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Almost 600 years ago a classical nova exploded in a flash so bright it was seen by astronomers from Seoul in Korea in the Scorpius constellation. It still holds astronomers’ attention today. Michael Shara, an astrophysicist at the American Museum of Natural History, searched for three decades to find the nova first witnessed by the Korean astronomers next to a pair of stars in Scorpius.

Shara’s paper shows part of Harvard photographic plate A 12424 on which the classic nova was recovered. This plate was generated by the 24-inch Bruce telescope at Harvard’s Boyden Station. According to from the Department of Physics at the UFS, the Bruce telescope was still in Arequipa in Peru at Harvard’s Southern Boyden Station when the photographic plate was taken in 1923.

Treasures discovered in the Harvard DASCH archive

“While reading Shara’s paper I realised that four other photographic plates in the paper showing a dwarf nova eruption of the recovered nova between April and June 1942 were generated by another Boyden telescope, the 10-inch Metcalf telescope while at its current home at the Boyden Observatory outside Bloemfontein. The telescope is currently used for educational purposes,” said Prof Hoffman. 

Upon being informed about the contributions of the photographic plates from Boyden Observatory near Bloemfontein, Shara responded: “Many thanks for sharing that really fascinating history and the great images; it would be wonderful to connect the name of the intrepid South African astronomer with the dwarf nova eruption images from 75 years ago! They were really essential in the publication of our SALT/Nature paper. It has garnered much press attention for SALT and South African telescopes, including feature articles in the New York Times, BBC, Science and others.” 

Prof Hoffman and his colleague and Boyden historian Dawid van Jaarsveldt found the historic logbooks in the Harvard DASCH archive and identified Mike Bester as the observer at the Metcalf telescope on the cold winter nights of 6 and 9 June 1942. Bester was an observer at Boyden Observatory for close to 40 years. “These glass plates are now being scanned to form part of the Harvard DASCH archive,” said Prof Hoffman.

The butterfly effect of stars

In a media statement Shara said that the plates from 1942 indicated that the star system is still “active”. The very bright classical nova had become a dwarf nova, less bright than it was when it was first spotted. Although dwarf novae are less bright, their eruptions repeat, blinking on and off over the course of years. In the 1980s, Shara predicted that novae and nova-like systems were the same stars in different stages of an eruption or morphing cycle. This classical nova, which he found with the help of the photographic plates at the Boyden Observatory, provided evidence that he was right. 

“The white dwarf that shed its hydrogen skin in the 1400s will do so again,” Shara said.