This animation is based on a series of spectra of the kilonova in NGC 4993 observed by the X-shooter instrument on ESO's Very Large Telescope in Chile. They cover a period of 12 days after the initial explosion on 17 August 2017. The kilonova is very blue initially but then brightens in the red and fades.More information: https://www.eso.org/public/videos/eso1733d/Credit:ESO/E. Pian et al./S. Smartt & ePESSTO/L. Calçada