Sh2-224 is a faint supernova remnant (SNR) located in the constellation Auriga. It is most commonly known as the Rice Hat Nebula. This is because its unique asymmetrical shape resembles a traditional Asian conical hat.
It is the expanding shell of debris. It was left over from a massive star’s explosion. This explosion occurred between 13,000 and 24,000 years ago. There are also 7 galaxies in the photograph.
The nebula spans roughly 163 light-years in diameter. The “hat” shape results from the supernova’s shockwave interacting with a lower-density cavity in the interstellar medium. This interaction allowed part of the shell to expand more rapidly into a “wing” or arc.
Sh2-224 is considered an extremely difficult target for amateur astronomers and astrophotographers because it is exceptionally dim. Capturing its detailed filamentary structure typically requires Long Integration Times: Often 20 to 60+ hours of total exposure.
This image is right at 8 hours of exposure. Image acquisition and session automation using APT. Subframe calibration, alignment, integration, and processing with PixInsight. Astrobin link for all the details.
