It is 1054, and suddenly a new star appears in the sky, so bright that not only can it be observed at night, it can be seen even during the day. Chinese astronomers record the new heavenly body as a “guest star”, because it is observed in the night sky for only 653 days before it disappears again.
Some 964 years later, Japanese amateur astronomer Koichi Itagaki is analysing pictures using his telescope. In one of the pictures, he spots a small bright dot that was not on previous images. He reports the dot, and professional astronomers follow up the discovery using larger telescopes.
Today, astronomers believe that the two observations, one from 1054 and one from 2018, have something in common. In both
