Sh2-157, commonly known as the Lobster Claw Nebula, is an emission nebula located in the constellation Cassiopeia at an approximate distance of 10,000 light-years. This complex H II region is energized by nearby massive stars whose ultraviolet radiation ionizes the surrounding hydrogen gas, producing strong H-alpha emission. Additional contributions from ionized oxygen and sulfur reveal regions of higher excitation and evolving shock fronts within the nebula.
The structure of Sh2-157 is shaped by the interaction between stellar radiation, stellar winds, and the surrounding interstellar medium. Dense regions of gas and dust form bright rims and cavities, while darker lanes trace colder, obscuring material embedded within the nebula. The characteristic “claw-like” morphology emerges from these interactions, with distinct lobes and ridges outlining areas of active star formation and gas compression.
This image was created using a combination of narrowband H-alpha, SII, and OIII data along with broadband RGB stars acquired from Arnold, CA. The data were collected between August 13 and September 27, 2024, with a total integration time of 48.6 hours . The image blends enhanced narrowband luminance with color-mapped emission data to highlight structural variations across the nebula while preserving natural star color and the broader context of this active star-forming region.