Sh2-135 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 colors, primarily due to the ionization of hydrogen gas by nearby hot stars. The nebula is approximately 2,500 light-years away from Earth. This nebula is also associated with the open cluster NGC 281, which contains young, hot stars that contribute to the nebula's luminosity. Sh2-135 is often studied by astronomers to understand the processes of star formation and the dynamics of interstellar gas and dust.