In 1181, a rare supernova explosion occurred in the night sky and could be observed for 185 days. This new image allows us to marvel at the same object our ancestors observed more than 800 years ago.

Historical records show that the supernova, seen in 1181 in the constellation Cassiopeia, appeared as a temporary ‘star’ as bright as Saturn.

Since then, scientists have been trying to find the remains of the supernova. Initially, it was thought that this could be the nebula around a pulsar called 3C 58 - the dense core of a collapsing star. But detailed analyses revealed that the pulsar is older than supernova 1181.

Another candidate has been discovered in the last decade: Pa 30, an almost circular nebula with a central star in the constellation Cassiopeia. This composite image was created by combining data from several telescopes and offers a spectacular new view of the supernova remnant. This allows us to marvel again at the same object that our ancestors saw in the sky more than 800 years ago.

ESA's XMM-Newton (blue) X-ray observations show the entire nebula, while NASA's Chandra X-ray Observatory (cyan) detects the central source. The nebula is barely visible in optical light but shines in infrared light collected by NASA's Wide-field Infrared Space Explorer (red and pink). Interestingly, the radial structure in the image is composed of heated sulfur glowing in visible light, observed with the ground-based Hiltner 2.4 m telescope at the MDM Observatory (green) in Arizona, USA. The background stars were observed by Pan-STARRS (white) in Hawaii, USA.

Studies of the composition of various parts of the remnant have led scientists to believe that the remnant was formed in a thermonuclear explosion, specifically a special type of supernova called a sub-luminous Type Iax event. During this event, two white dwarf stars merged, and usually no remnant is expected from this type of explosion. However, 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 (about 200,000 degrees Celsius), has a fast stellar wind reaching speeds of 16,000 kilometres per hour. The combination of star and nebula provides a unique opportunity to study such rare explosions.

Image Description:

This is a composite image of SNR 1181, the remnants of an explosion centuries ago when two stars merged. A bright, multi-coloured, spherical nebula is in the centre of the canvas, surrounded by stars that appear as white dots. In the centre of the nebula is a small point of light the colour of water. This is the hot white dwarf star left over from the explosion that occurred after the merger of two small white dwarfs. From this single water-coloured point of light, several spectacular rays radiate outwards, resembling fireworks exploding in the night sky.