Binary Star Explosion

For the first time in over 100 years, scientist have witnessed the explosion of a binary star inside a planetary nebula. Astronomers at University College London predict that the two stars eventually may spiral into each other and trigger a much larger supernova explosion. 

A planetary nebula is a glowing shell of gas and plasma formed by certain types of stars when they reach the red giant phase of their lives. During this phase, the outer layers of the star are expelled by strong pulsations and solar winds. The core of the star then emits ultraviolet radiation that ionises these ejected layers, and they radiate out as a planetary nebula. 

A nova, on the other hand, is nuclear explosion caused by accretion of hydrogen onto the surface of a nearly-dead white dwarf star.  In a closed binary system, the nova occurs as matter is transferred from one star to the other, which eventually causes a cataclysmic thermonuclear explosion. Novas are in themselves not uncommonly observed, but a nova inside a planetary nebula is rarely seen. The nova illuminates the surrounding gases and plasma as the light passes through it, and the UCL scientist say this could help us understand more about the life cycle of stars. 

The has been given the name V458 Vulpeculae, and it could turn out to provide researchers with an opportunity of observing how a nova might evolve into a supernova. 

The top image was taken in May 2008, and the bottom in September 2008. The changes that occur due to the ongoing nova are clearly visible. From University College London.