What causes the swirl in the Shrimp Nebula?
Its high speed is likely.
What is sure is that
Sh2-188 is one of the larger
planetary nebulas on the night sky,
by
angular size, spanning about half the
diameter of the Moon.
Moreover, the
white-dwarf core -- leftover from the
Sun-like star
that shed its outer atmosphere -- is moving
unusually fast through interstellar space, creating a
bow shock most visible
on the upper left that is
similar to
a boat plowing
through water.
Although faint, the
Shrimp Nebula
glows also by
compressing and brightening gas on its leading edge.
The
featured image was taken in the light of
hydrogen, sulfur, and oxygen by a backyard telescope in
Krakow,
Poland and then
digitally adjusted to approximate
the nebula's
true colors.