A Celestial Crustacean in the Milky Way
Sh2-132 is a massive HII region energized by several hot, massive stars, including the Wolf-Rayet star WR 157. The 'Claw' is formed by two main filaments of ionized gas that stretch out into the interstellar medium. Within the northern 'pincer' lies a very bright, compact emission region known as Sh2-157a (or Lynns' Nebula), which is often mistaken for a planetary nebula but is actually a small, dense star-forming knot. The entire complex is a beautiful example of how stellar winds from massive stars can shepherd gas into long, elegant arcs.
Imaging Challenges
- • Faintness: The main 'body' of the claw is quite diffuse and requires a lot of integration time to smooth out the noise.
- • Oxygen Signal: There is a beautiful OIII 'glow' inside the claw that is much fainter than the Ha, requiring careful stretching.
- • Busy Field: Like its neighbors, it is embedded in a very dense star field that can easily obscure the nebulosity.
The 'bright spot' in the pincer (Sh2-157a) is so intense that it can be captured in relatively short exposures, even while the rest of the claw remains invisible.