| Description |
V838 Mon is one of the most enigmatic objects observed in stellar astrophysics in recent decades. It came to attention when it underwent a powerful eruptive outburst in Jan. 2002, increasing in luminosity by a factor of 100 over a period of 3 months. Immediately following this event a spectacular light echo was formed from the outburst light reflecting off the surrounding dust. Hubble Space Telescope images following this expanding light echo have brought V838 Mon to public attention. What makes V838 Mon an unusual star is that the outburst is not of any type heretofore seen; the scenarios of a nova-like event or thermonuclear runaway have been discounted, on the basis of the stellar type and outburst details. The theories that best explain the outburst are a giant star engulfing a planetary system or, more likely, a merger between a very low mass star and a very young, maybe pre-main sequence low-intermediate mass star. Observations show that the envelope of the star expanded in response to the stellar impact, and than it may now be beginning to contract. Many O-bearing molecules, dust, an SiO maser and possibly a jet have been observed from the star. If the outburst was indeed caused by the merging of two stars, this is an extremely rare event. Herschel observations of this star will allow us to model the kinematics, chemistry, temperature and density structure of the stellar photosphere and the cool envelope surrounding the star. These will help answer questions still remaining about the stellar impact, and will also allow us to understand more about how a star responds to such a violent event. |
