V838 Mon is one of the prettiest exploded star remnant formations. It is located about 20,000 light-years away from Earth in the direction of the constellation Monoceros, placing the star at the outer edge of our Milky Way galaxy. In early 2002, astronomers witnessed an enormous explosion emanating from V838 Monocerotis as it burst. It created an expanding light echo – where light from a stellar explosion bounces off dust surrounding the star – which the Hubble telescope captured. The light eruption was so bright that for a while it was one of the most luminous stars in the Milky Way. The remnant is evolving rapidly. By 2009 its temperature had increased to 3,270K and its luminosity was 15,000 times more than our Sun, but its radius had decreased to 380 times that of the sun although the ejecta continues to expand.
Obtained with the Advanced Camera for Surveys (below), is Hubble’s latest view of an expanding halo of light around V838 Mon. The illumination of interstellar dust comes from the red supergiant star at the middle of the image, which gave off a flashbulb-like pulse of light two years ago.