Nova Delphini 2013 spectrum,as recorded on 16 August 2013 (top) and 29 August 2013 (bottom). The nova (a sudden brightening of a star) was discovered on 14 August. At top,it is near its peak brightness,about 10,000 times brighter than normal. Emission lines in the spectrum,caused by the nova,shift as the resulting gas cloud expands. In the second spectrum,the nova is fading,but bright emission lines are still present due to excitation of the expanding gas cloud by UV radiation from the star. Elements present include hydrogen,but also some iron from the star's interior. These observations took place at the observatory at Bulach,Switzerland |