The Light Echo Around V838 Monocerotis Reveals Dramatic Changes over a Decade

The expanding illumination of interstellar dust around the unusual, variable star called V838 Monocerotis (V838 Mon) is known as a light echo. The star has been revealing remarkable structures in the dusty cloud ever since the star suddenly brightened in January 2002. V838 Mon temporarily became 600,000 times brighter than our Sun, until it faded in April 2002. The reason for the eruption is still unclear.

The light from V838 Mon scatters or "echoes" off the dust. Because of the extra distance the scattered light travels, it reaches Earth long after the light from the stellar outburst itself.