Once every few weeks, the star system Z Camelopardalis pops off. It flares to about 50 times its normal brightness, then slowly fades. But at least once in the last couple of thousand years, it probably flared thousands of times brighter than its normal outbursts — like the difference between a flashlight and a searchlight. And today, astronomers can still see the residue of that blast.

The system is in Camelopardalis, the giraffe. The constellation is about half way up the north-northeastern sky at nightfall.

Z Cam consists of two stars. One is a white dwarf — the small, hot corpse of a once-normal star. Its companion is much like the Sun. The stars are so close together that the white dwarf “steals” some of the companion’s gas. The gas forms a swirling hot disk around the white dwarf. Every few weeks, the disk falls onto the white dwarf, creating an outburst.

But a few years back, astronomers discovered a shell of gas and dust around Z Cam. It’s several light-years wide, suggesting it’s been expanding into space for a long time.

The shell probably was produced in a much more powerful outburst. Lots of gas from the companion built up on the white dwarf. This material got so hot that it triggered a nuclear explosion, blasting the layer of gas into space.

The blast was so bright that it might have been visible from Earth. In fact, Chinese astronomers might have recorded it — 2100 years ago.

Script by Damond Benningfield

Support McDonald Observatory