The GIF below is copied from my question earlier What might a CN filter be in the context of comet watching? Is it showing dust, or gas, or something else? where I'd said:
It certainly looks like the comet is spinning; it reminds me of images of the density of the solar wind as active areas on the sun "spray" out matter as the Sun rotates, or the patterns discussed in Why is one of these two concurrent fuel-dump spirals blue?.
Question: This leeds me to wonder if I'm just imagining things, or if some comets really do spin? If so, how fast have they been observed to rotate?