Crab Nebula Supernova Observations
Ancient Chinese Records of the July 4, 1054 Supernova
The supernova that formed the Crab Nebula in 1054 was observed by the ancient Chinese, but there are no known western observations.
Supernovae
A supernova is a huge stellar explosion involving the entire star. The supernovae that mark the death throes of massive stars, Type II supernovae, play a crucial role in forming the atoms in our bodies. A supernova explosion can release as much energy in a little over a year as the Sun does in its entire 10 billion year lifetime. Although they are common on cosmic time scales, supernovae in our own galaxy are rare on human time scales. Only about a half dozen have been observed in our own galaxy in recorded history. One well known supernova is the one that formed the Crab Nebula.
Crab Nebula Supernova
A supernova occurring on July 4, 1054 formed the Crab Nebula, a well known supernova remnant in Taurus. The ancient Chinese recorded detailed observations. It was a previously unseen star that became for a time bright enough to be visible in the daytime. It may have also been observed by the Anasazi people of the US southwest.
Chinese Observations
Chinese written records provide our most accurate data on historic supernovae. The ancient Chinese had a highly developed civilization that kept written astronomical records dating back thousands of years. They often recorded what they called guest stars that appeared where no star had previously been observed. The guest stars were often extremely bright for a short time then gradually faded back into their familiar obscurity.
We now know that these guest stars are stellar explosions and call them either novae or supernovae. Because the entire star explodes supernovae are more violent explosions than novae, which only involve the surface layers of a white dwarf. The Crab Nebula is the remnant of the supernova that the Chinese observed in 1054. How do we know? In 1921 C.O. Lampland discovered that the Crab Nebula is expanding. Working back, it is expanding from an explosion that occured in the 11th century, the July 4, 1054 supernova explosion.
According to Chinese records, on July 4, 1054 AD a very bright guest star appeared close to the star they called the heavenly gate, Tien-Kwan, which we now know as the star Zeta Tauri. At its peak this guest star was visible in the daytime for a period of 23 days. It slowly faded and disappeared from view altogether in the spring of 1056, nearly two years later.
In the ancient Chinese tradition the spirits of their emperors, and other high officials, travel to Tien (heaven) after death by passing through Tien Kwan. The heavenly gate, Tien Kwan, therefore represents the transition from the earthly life to the afterlife for the emperor. Supernovae explosions are the death throes of massive stars, so in addition to marking the deaths of Chinese emperors, Tien Kwan also marks the death of a massive star.
Further Reading
Zeilik, Michael, Astronomy the Evolving Universe, 9th edition, Cambridge, 2002.
