The V838 Mystery Star

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. Then, just as suddenly, it faded. A stellar flash like this has never been seen before -- supernovas and novas expel matter out into space. Although the V838 Mon flash appears to expel material into space, what is seen in the above four-frame movie is actually an outwardly moving light echo of the bright flash.

Light from the outburst is reflected by successively more distant rings in the complex array of ambient interstellar dust that already surrounded the star. The actual time-span between the first and last frames is 8 months during 2002. The star lies about 20,000 light years away toward the constellation of Monoceros, while the largest light echo above spans about 6 light years in diameter. Did the light from the flash travel 3 light years outward from the star in only 8 months? If so, it was moving at 4.5 times the speed of light. A good astrophysical explanation for V838 Mon's outbursting behavior is still unknown but astronomers continue to follow the mystery star.