The beauty of the starry sky sometimes lies not in the bright stars, but in the magnificent treasures hidden in them.

For example, near the horns of the "unicorn" in the constellation Monoceros, although there are no bright stars visible to the naked eye, they are located right in the middle of the Milky Way, and in the long exposure of the camera, the faint stars are densely packed all over the picture. But they are not the real protagonists of this region of the sky.

If you look closely, among the stars, you can see a large red patch - a large cloud of ionized hydrogen in the Orion Arm of the Milky Way, about 2700 light-years from Earth. This red color comes from the hydrogen in the nebula. This simplest element is also the most abundant in the universe. When exposed to ultraviolet light from surrounding young stars, hydrogen ionizes and emits this distinctive, festive color.

The different parts of this hydrogen cloud with different shapes have also incarnated into many deep space treasures. The most famous of these is around the bright blue star in the lower center of the image, called the Christmas Tree Cluster. Every time around Christmas, it will be on the front page of various astronomy websites. Unfortunately, I do not see what the tree looks like, but rather the cone-shaped nebula on the right and the fox-skin nebula on the upper left, which is very realistic.

Other components of the hydrogen cloud add rich colors and layers to this red. For example, the blue glow at the top of the image is the reflection nebula IC 447, a cloud of dust scattering the light of neighboring stars. The reason for its blue color is similar to the blue sky on Earth, because blue light is more easily scattered by tiny dust or gas molecules. At the top left of the Christmas tree cluster, the opaque dust has cut out a dark silhouette in the red hydrogen cloud, an ethereal image that is indistinguishable from anything else, but equally fascinating.

If it weren't for the camera's long exposure to accumulate weak signals, if it weren't for post-processing to weaken the star points and strengthen the background, these deep-sky treasures hidden among the stars would not have been appreciated by our human eyes, which are naturally inadequate for dark light.