In July 1054 Chinese astronomers saw a reddish-white star appear in the eastern sky, its “rays stemming in all directions.” Yang Weide wrote:

I humbly observe that a guest star has appeared; above the star there is a feeble yellow glimmer. If one examines the divination regarding the Emperor, the interpretation is the following: The fact that the star has not overrun Bi and that its brightness must represent a person of great value. I demand that the Office of Historiography is informed of this.

It’s now believed they were witnessing SN 1054 — the supernova that gave birth to the Crab Nebula.