Symbiotes

A star system in the constellation Andromeda is always hoppin’. Its two stars interact with each other, triggering brilliant outbursts.
Z Andromedae consists of two stars locked in a mutual orbit. In fact, it’s the prototype of a broad class of binaries, known as symbiotes because they interact with each other.
One of the stars is a red giant — an old, bloated star that’s about a thousand times brighter than the Sun. The other is a white dwarf — the exposed core of a once-normal star. Unlike most white dwarfs, it’s “burning” a thin layer of hydrogen on its surface. Because of that, it’s also a thousand times brighter than the Sun.
Occasionally, though, Z Andromedae gets much brighter. What’s happening isn’t fully understood. But one scenario goes something like this.
The red giant spews a strong wind of charged particles. Some of the particles go into orbit around the white dwarf, forming a wide disk. Material in the inner part of the disk falls on the surface of the white dwarf.
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