Description:
Sh2-188 is a faint but striking planetary nebula located in the constellation Cassiopeia, about 850 light years away from Earth.
Its structure is highly asymmetric: a bright, filamentary arc to one side, with fainter wisps trailing behind it. This unusual morphology reveals important details about its history and environment.
At the heart of Sh2-188 lies WD 0127+581, a hot DAO white dwarf (Centre of the 2 yellow lines I added in the image).
This star is the remnant of a Sun-like star that shed its outer layers near the end of its life.
The intense ultraviolet radiation from the white dwarf ionizes the ejected gas, causing the nebula to glow.
Astronomers believe the nebula’s odd “one-sided” appearance results from the central white dwarf moving rapidly through the interstellar medium (ISM).
As the stellar wind from the dying star collides with the ISM, the material is compressed into a bow shock at the front, forming the bright arc.
Behind the star, the gas trails into long faint filaments, resembling a comet’s tail.
This process makes Sh2-188 a textbook example of a planetary nebula shaped by stellar motion and external forces, rather than being purely spherical.