The Variable Stars In Our Sky
On 14 August 2013 Koichi Itagaki, an amateur astronomer in Yamagata, Japan spotted a “new star”, as people centuries ago would have conceived it, on an image he had taken of the constellation Delphinus, it was in fact a “nova”, eventually earning the catalogue entry V0339 Delphini.
A nova results from a runaway thermonuclear explosion at the surface of a white dwarf star after years of gas exchange from a companion star onto the dwarf. In less than an hour, a shell of material begins to expand at around a thousand kilometres per second. Unlike a supernova, such an event doesn’t destroy the progenitor star system, nor does it release as much energy.
By 17 August, the nova had peaked in brightness, becoming briefly visible to the unaided eye from a suitably dark location. The rise from pre-nova to peak brightness represents an increase in luminosity of thousands of times that of our Sun.
This relatively rare event went largely unreported in the mainstream media, but to many amateur astronomers, the nova was captivating.