1054: A supernova noted by Chinese observers heralds the creation of the Crab Nebula. The exact date has been disputed, but most accounts accept the Chinese date of July 4.

Supernova 1054, as it is now known, was spotted in the constellation Taurus by Chinese astronomers, who recorded no fewer than 75 supernovas (or "guest stars," as they called them) between 532 B.C. and A.D. 1064. In this case, however, the magnitude was unusually large: The star shone roughly four times brighter than Venus and was visible in daylight for 23 days.

It remained visible in the night sky for 653 days.

The remnant of that exploding star is what we now know as the Crab Nebula. The nebula itself wasn't officially recorded until 1731 by English astronomer John Bevis.

The Chinese weren't the only ones to make an early sighting: Astronomers in the Arab world provided their own accounts, and archeological evidence found in North America suggests that Indian sky watchers also recorded the supernova.

(Source: Various)

This article first appeared on Wired.com July 4, 2007.