Explanation: What caused this outburst of V838 Mon?
For reasons unknown, star V838 Mon's outer surface suddenly greatly expanded with the result that it became the brightest star in the entire Milky Way Galaxy in January 2002.
Then, just as suddenly, it faded.
A stellar flash like this has never been seen before -- supernovas and novas expel matter out into space.
In a light echo, light from the flash is reflected by successively more distant rings in the complex array of ambient interstellar dust that already surrounded the star.
