In 1006 A.D., observers from Africa to Europe to the Far East recorded the arrival of light from what is now called SN 1006, a tremendous supernova explosion of a white dwarf star nearly 7,000 light-years away. The supernova was probably the brightest star ever seen in recorded times. It surpassed Venus in the night time sky, only being outshone by the moon. It was visible during the day for weeks, and remained visible to the naked eye for at least two and a half years before fading away.
About 50 years ago, radio astronomers detected a nearly circular ring of material at the recorded position of the supernova. The ring was almost the same angular diameter as the full moon. The size of the remnant implied that the blast wave from the supernova had expanded at nearly 20 million miles per hour over the nearly 1,000 years since the explosion occurred.
Today, we know that SN 1006 has a diameter of nearly 60 light-years, and is still expanding at roughly 6 million miles per hour. Even at that speed, however, it takes observations years apart to detect significant outward motion of the shock wave. This Hubble image of a delicate ribbon of gas shows a very thin section of the supernova remnant. The location of the 1006 explosion is well out of the farme to the lower left. The shock wave is moving to the upper right.
Image Credit: NASA