The quiet explosion (annotated)

Images at three different epochs of the spiral galaxy NGC 2770, located 90 million light-years away towards the Lynx constellation, observed from the Asiago Observatory. The first image on 6 January 2008 reveals only the fading supernova SN 2007uy, which was discovered at the end of 2007. The second image, taken 6 days later, shows the newly discovered supernova SN 2008D. It is very rare for two supernovae to happen at the same time in a galaxy, as a supernova on average happens only once every hundred years. The last one to have been seen in our Milky Way dates back from 1604. The third image, taken almost a month later, still shows the two supernovae. SN 2007uy has faded, while SN 2008D brightened. The small animation shows an interpolation between these three images.