1054

“Daytime Star” Observed

By the end of the early Middle Ages, a number of societies on the planet had flourishing or nascent communities of astronomers and mathematicians who were tuned in to the heavens. It is perhaps of little surprise, then, that when a new star suddenly and dramatically appeared in the sky in the constellation Taurus in the year 1054, many of those societies took notice.

Chinese astronomers first recorded the appearance of a “Guest Star” on July 4. Their observations were corroborated by Persian, Arab, Japanese, and Korean observers; the event was even recorded in rock paintings by Native American Anasazi artists. Europeans, still mired in the Dark Ages, didn’t seem to record the event. Chinese observers saw the new star in the daytime for 23 days, and at night for 653 days, until it faded away. At maximum brightness, it was estimated to be around magnitude −6 or −7, brighter than everything in the sky except the Sun and Moon.

We now know that what these medieval astronomers had observed was a supernova—the violent, catastrophic explosion of a massive progenitor star about 6,300 light-years from Earth that ran out of fuel for nuclear fusion and collapsed in on itself, releasing an enormous amount of gravitational energy that expelled the star’s outer layers into space at enormous speeds, perhaps as high as 10 percent of the speed of light. More than 650 years after the supernova faded from view, eighteenth-century astronomers first detected the crab-shaped emission nebula of ionized gases being heated by the explosion’s shock wave. In the late 1960s, radio astronomers discovered that the compressed core of the original star had become a rapidly spinning (30 times per second) neutron star, or pulsar, that is probably only about 12 miles across but has a mass of about 1.5 to 2 times that of the Sun. The careful records of this event by early astronomers helped to establish the previously unknown link between supernovae, emission nebulae, and neutron stars.

The inset shows an Anasazi petrograph depicting a hand, crescent Moon, and the new “guest star” of 1054.

SEE ALSO Birth of the Sun (c. 4.6 Billion BCE), Astronomy in China (c. 2100 BCE), Chinese Observe “Guest Star” (185), Nuclear Fusion (1939), Pulsars (1967).

Hubble Space Telescope mosaic of the Crab Nebula, a six-light-year-wide expanding remnant of ionized gas from a violent supernova explosion seen by medieval astronomers in the year 1054.