V838 Monocerotis (V838 Mon) is a red variable star in the constellation Monoceros about 20,000 light years from the Earth. It was first observed in early 2002 experiencing a major outburst, and it was one of the largest known stars for a short period following the outburst. At first, V838 Mon was thought to be a typical nova eruption, but it is now known to be something completely different. Just what is still uncertain, but a couple of the possibilities are an eruption related to stellar death processes or a merger of a binary star or planets.
The remnant is evolving rapidly.
Video Credit: NASA