The Lobster Claw Nebula, Sh2-157 in Cassiopeia, with the Bubble Nebula (NGC 7635) and its neighbours in the same frame. The Lobster Claw is a big cloud of hydrogen about 11,000 light-years away, lit by giant stars including the Wolf-Rayet star WR 157, whose winds help carve its ring shape. The Bubble is blown by a single star, BD+60 2522, about 45 times the mass of the Sun, whose wind streams out at more than 4 million miles per hour and inflates a shell into the cold cloud around it. The open cluster M52, next to the Bubble, is only about half as far away, about 5,000 light-years, so it sits in the foreground. At the top of the frame is NGC 7538, about 8,600 light-years away, a nursery where some of the most massive stars in our part of the galaxy are forming right now.
The colours are the HOOSy palette, the way Ulf Backmeyer of Hellas-Sky processes this object: hydrogen and oxygen first (HOO), the hydrogen turned down and the oxygen up with narrowband normalisation, then the sulphur added into the red for depth. Hydrogen reads gold-orange, oxygen blue, and the claws show both. No hue shifts, no SCNR. The stars are their real colours, from separate red, green and blue exposures.