Sh2-187 is a bright emission nebula located in the constellation of Cassiopeia. It is part of a larger region of star formation and is known for its striking appearance, which is primarily due to the ionization of gas by nearby hot stars. The nebula is approximately 10,000 light-years away from Earth. This nebula is also associated with the H II region, where hydrogen gas is ionized by ultraviolet light from young, massive stars. Sh2-187 is often studied by astronomers to understand the processes of star formation and the dynamics of interstellar matter in our galaxy.