Celestial processes normally take thousand of years, or even millions or billions. The night sky we observe today (minus the modern particulate and light pollution) is insignificantly different from that our ancestors observed 2000 years ago. Aside from local events like eclipses, comets, or asteroid encounters, it’s pretty rare to see something in the sky that is really really big and also really really fast. Well, it’s all relative, of course. In the case of the star called V838 Mon (in the constellation Monoceros, about 20K light years away) a singular event happened in 2002 that caused an insanely huge explosion that was captured in time-lapse over a period of four years by our good friend the Hubble Space Telescope. It’s not clear what was the cause of the explosion, but apparently it was not a nova as originally thought. In any case it was momentarily one of the largest stars ever observed (settling to the size of a mere 380 solar radii) and produced some 600,000 times more light than the sun. This video was captured from 2002 to 2006 and is NOT a simulation, though they did morph the still images to smooth the transitions.