In the year 1181 a rare supernova explosion appeared in the night sky, staying visible for 185...
In the year 1181 a rare supernova explosion appeared in the night sky, staying visible for 185 consecutive days.
Historical records show that the supernova looked like a temporary 'star' in the constellation Cassiopeia shining as bright as Saturn.
Ever since, scientists have tried to find the supernova's remnant.
In the last decade, another contender was discovered; Pa 30 is a nearly circular nebula with a central star in the constellation Cassiopeia.
The nebula is barely visible in optical light but shines bright in infrared light, collected by NASA's Wide-field Infrared Space Explorer.
Interestingly, the radial structure in the image consists of heated sulphur that glows in visible light, observed with the ground-based Hiltner 2.4 m telescope at the MDM Observatory in Arizona, USA, as do the stars in the background by Pan-STARRS in Hawaii, USA. Studies of the composition of the different parts of the remnant have led scientists to believe that it was formed in a thermonuclear explosion, and more precisely a special kind of supernova called a sub-luminous Type Iax event.
During this event two white dwarf stars merged, and typically no remnant is expected for this kind of explosion.
Incomplete explosions can leave a kind of 'zombie' star, such as the massive white dwarf star in this system.
This very hot star, one of the hottest stars in the Milky Way, has a fast stellar wind with speeds up to 16 000 km/h.
The combination of the star and the nebula makes it a unique opportunity for studying such rare explosions.