V838 Monocerotis is a spectroscopic binary star system in the constellation Monoceros about 19,000 light years from the Sun. The previously unremarked star was observed in early 2002 experiencing a major outburst, and was one of the largest known stars for a short period following the outburst. Originally believed to be a typical nova eruption, it was then identified as the first of a new class of eruptive variables known as luminous red novae. The reason for the outburst is still uncertain, but is thought to have been a merger of two stars within a triple system.
Hubble Space Telescope image of V838 Monocerotis and the surrounding nebula on September 9, 2006 Credit: NASA/ESA
Light echo of V838 Mon as imaged April 30, 2002
Images showing the expansion of the light echo. Credit: NASA/ESA.
Two pictures taken in November 2005 and September 2006 showing the changes that occurred to the bright echo of V838 Mon.
Monoceros is a faint constellation on the celestial equator. Its definition is attributed to the 17th-century cartographer Petrus Plancius. It is bordered by Orion to the west, Gemini to the north, Canis Major to the south, and Hydra to the east. Other bordering constellations include Canis Minor, Lepus, and Puppis.
The constellation Monoceros as it can be seen by the naked eye.
The constellation Monoceros, from Urania's Mirror, a set of star charts from 1825. Includes Canis Minor and the obsolete constellation Printer's Workshop
