WHAT LIT UP THE SKY IN 1054?

The Crab Nebula was formed by a supernova, and astronomers now think they know which type caused it

- David Crookes

In 1054 CE, Chinese astronomers looked towards the sky and discovered a star that had suddenly appeared in a position 6,500 light-years away from where no star had previously been observed. They watched as it shone six times more brightly than Venus in the constellation of Taurus for 23 days from 4 July, and their observations were backed by astronomers in Japan and the Arab world.

Reported as a ‘guest star’ by the chief of the astronomical bureau at K’ai-Feng, it remained visible until 17 April 1056. It would then be another 872 years before Edwin Hubble became the first to associate the observation with another discovery – that of the Crab Nebula, which was spotted in 1731 by English astronomer John Bevis.

Hubble suggested that what the Chinese astronomers had seen was a supernova explosion that had caused stellar remains to be scattered across an area of space some six light-years wide. It was a controversial theory, primarily because the study of supernovae was still in its infancy. But in 1939, American observational astronomer Nicholas Mayall demonstrated beyond doubt that the two were linked.

Having established that the ‘guest star’ of 1054 was a supernova – a term first used in the 1930s by Walter Baade and Fritz Zwicky at Mount Wilson Observatory – astronomers had many questions. Was the date of the explosion correct, for instance, and were reports of the celestial fireworks consistent. In those cases, possibly yes and not entirely are found to be the general answers.