Near the head of the constellation Scorpius glows an immense red gas bubble like a celestial ghost. It has a diameter of 10 degrees, which corresponds to the size of a fist held at arm’s length. The innocuous name of this vast expanse of hydrogen gas is Sharpless 2-27.
In spite of its enormous size it is invisible to human eyes and even astrophotography almost always fails to capture it. Only a handful of photographs exist of this large but elusive object, because the nebula is way too large for any telescope and it has an extremely low surface brightness. That is why we used a short focus 50mm lens on a DSLR camera as well as special H-alpha filtering techniques to enhance the hydrogen emission line of the nebula.
The actual distance of the obscure nebula Sh2-27 still remains uncertain. Estimations are around approximately 500 light years, which would mean the gas cloud spans about 100 light years across. The bright star in the center of the image is Zeta Ophiuchi, a hot O type runaway star probably ejected from a binary system a long time ago. It will go supernova in the next few million years.
Deep images like this can only be obtained from locations where no light pollution is present. In this case, the image was shot by project nightflight astrophotographers from La Palma island in the Atlantic Ocean. More than 60 individual exposures with a total exposure time of 4 hours were digitally combined to bring out the faint details.
Source: Project Nightflight