This week back in 1181, ancient astronomers in China and Japan recorded the appearance a “guest star.” Today we call those a supernova, but I think I prefer guest star. It was a star that appeared where there was no star before. It was visible for a time, and then it was gone.

How strange it must have seemed to them appearing in the sky which they observed and recored so carefully and which changed through the season – but with a predictable regularity. That is a regularity that almost every ancient civilization relied upon, trusted and perhaps worshiped.

This particular guest star was located in a place shared by several constellations. For them, it appeared in the Black Tortoise of the North and the White Tiger of the West.

Historians have found eight different references to the event.

In the Western part of the world where astrological references are primarily to the ancient Greeks, it appeared in the constellation Cassiopeia.

The new star was one of the three most brilliant objects in the sky and remained visible for six months before disappearing again.

X-Ray image of 3C58 by Chandra X-Ray Observatory. The pullout box shows the inner toroidal-shaped nebula - image via

This supernova is now known by the totally un-Romantic name SN 1181. It is one of only eight supernovae in the Milky Way observable with the naked eye in recorded history. The Chandra X-Ray Observatory has given us a view of the remnants of that supernova of 1181 and that remnant carries the label 3C58. (Technically, it’s a pulsar wind nebula (AKA “plerion”, from Ancient Greek “pleres” meaning “full”)

I like the idea that this nebula is powered by the pulsar wind of a pulsar. Wind blowing in space is a rather poetic rather than scientific way of describing things. Astronomers consider it to be in its “early stage” which means the first few thousands of years of its evolution.

What the guest star left behind (like a gift that your house guest left to remind you of their visit) is an oval of matter glowing with X-rays and radio waves. It is 10,000 light years away. Can you even imagine that distance? At its center is a rapidly spinning neutron star. From that center comes jets of particles moving at near the speed of light. Each jet sweeps the sky and appears to flash on and off fifteen times each second like a gigantic lighthouse beam against the backdrop of the sky.