Supernova of 1006: The New Star That Cast Shadows at Night

The brightest star in recorded history: a new light in 1006 bright enough to cast shadows, logged from Egypt to China.

In late April or early May 1006 CE a new star appeared in the constellation Lupus. It was the brightest stellar event ever recorded, bright enough to cast shadows and visible in daylight for a time.

In late April or early May of 1006 CE, a new star appeared in the southern constellation Lupus, the Wolf. It was the brightest stellar event ever recorded, estimated at magnitude around minus 7.5, far brighter than Venus. It was visible even in daylight for a time and remained in the night sky for months.

Observers around the world wrote it down. The Egyptian astronomer and physician Ali ibn Ridwan, in Cairo, described it as two and a half to three times the size of Venus, lighting the ground with a brightness a little more than a quarter of the moon's. Chinese court astronomers recorded it and debated its meaning. It was noted in Japan, in Iraq and Yemen, and in the annals of the Swiss abbey of St. Gall.

Astronomers identified the remnant in the twentieth century: a shell of hot, expanding gas about 7,000 light years away, now studied with X-ray and radio telescopes. The explosion is thought to have been a Type Ia supernova, the thermonuclear destruction of a white dwarf star. Its edges are sites where particles are accelerated to extreme energies, making it a natural laboratory for studying cosmic rays.

SN 1006 shows how ancient and medieval sky records can be matched to real astronomical events. It also shows that a new, shadow-casting light in the sky, which to many cultures would have been a sign from heaven, can be a natural event. It is also a reminder that the ancient sky could change dramatically, and that careful watchers recorded it.