SN 1006, the brightest supernova on record

In late April or early May 1006 a new star appeared in the constellation Lupus, low in the southern sky. Chinese court astronomers of the Song dynasty logged it and watched it for months. The Egyptian astronomer Ali ibn Ridwan, writing in Cairo, described it as a bright body with a large disc and said its light was about a quarter that of the Moon. Records also survive from Japan, Iraq and the monastery of St. Gall in Switzerland.¹

Modern estimates put its peak at roughly magnitude minus 7.5, far brighter than Venus and the brightest supernova seen from Earth in recorded history. The remnant, found by radio astronomers in 1965, lies about 7,000 light years away and is the leftover of a white dwarf that exploded. Medieval observers had no idea what it was. Many Europeans and Muslims read such events as omens, while Chinese astronomers filed it as a guest star. Today the multiple independent records let astronomers check its position, timing and brightness, which helps calibrate distance measurements for supernovae.¹²