| Description |
V838 Mon is one of the most enigmatic objects observed in stellarastrophysics in recent decades. It came to attention when it underwenta powerful eruptive outburst in Jan. 2002, increasing in luminosity by afactor of 100 over a period of 3 months. Immediately following this eventa spectacular light echo was formed from the outburst light reflecting offthe surrounding dust. Hubble Space Telescope images following thisexpanding light echo have brought V838 Mon to public attention. Whatmakes V838 Mon an unusual star is that the outburst is not of any typeheretofore seen; the scenarios of a nova-like event or thermonuclearrunaway have been discounted, on the basis of the stellar type andoutburst details. The theories that best explain the outburst are a giantstar engulfing a planetary system or, more likely, a merger between avery low mass star and a very young, maybe pre-main sequencelow-intermediate mass star.Observations show that the envelope of the star expanded in responseto the stellar impact, and than it may now be beginning to contract. ManyO-bearing molecules, dust, an SiO maser and possibly a jet have beenobserved from the star. If the outburst was indeed caused by the mergingof two stars, this is an extremely rare event. Herschel observations ofthis star will allow us to model the kinematics, chemistry, temperatureand density structure of the stellar photosphere and the cool envelopesurrounding the star. These will help answer questions still remainingabout the stellar impact, and will also allow us to understand more abouthow a star responds to such a violent event. |
