A poem of praise for the famous sultan Salah ad-Din Yusuf ibn Ayyub (Saladin) has been misdated, a new paper argues, and refers not to an unusually close planetary conjunction but to the supernova of 1181. If the claim is correct, the poem’s words could be of scientific value to astronomers hoping to establish how bright the event would have been from Earth, and how long it took to fade. The rest of this article is behind a paywall. Please sign in or subscribe to access the full content.

In 1181 and 1182, Chinese and Japanese astronomers reported a “guest” star appearing in the northern sky before fading away. Modern astronomers have puzzled over whether this was a nova or a supernova, and in the latter case, which type. Remarkably, it was only 12 years ago that amateur astronomer Dana Pa

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