science & techThe Public Domain Review964 · Isfahan, Persia

Behold the Nebulous Smear: ‘Abd al-Rahmān al-Sūfī’s *Illustrated Book of Fixed Stars* (ca. 1430)

the gist

In 964, the Persian astronomer Abd al-Rahman al-Sufi completed the Book of Fixed Stars, which described constellations as seen from both outside and inside the celestial sphere. He corrected Ptolemy's star positions, which had drifted over the centuries, and added traditional Arabic names for many stars. In his notes he described a faint cloudy patch in the constellation Andromeda, now known to be the Andromeda Galaxy, the first written mention of a galaxy other than the Milky Way.

so what

Al-Sufi's book was an important observational astronomy text that preserved and extended Greek knowledge, and it was copied for centuries. His description of the Andromeda Galaxy is one of the earliest recorded observations of an object beyond our own galaxy.

Image: The Public Domain Review