File:Glowing Red at Kitt Peak (iotw2404a).tiff

English: Our home galaxy, the Milky Way, appears like a halo of light arching over the MDM Observatory’s Hiltner 2.4-meter Telescope at Kitt Peak National Observatory (KPNO), a Program of NSF’s NOIRLab. The whites of starlight and bluey black of shadowy trees feel commonplace on a dark night — but the reds in this image seem to cover the environment. What are the red clouds blooming in the sky? Why is there red light on the observatory?The red clouds are emission nebulae, clouds of gasses that have been so energized that they have lost some or all of their electrons. These gasses then emit light at various wavelengths, hence the name. These clouds look red because of the abundance of hydrogen. The largest of these blooms, located at the left end of the arch, is the Gum Nebula.What about the red lights on the ground? In order to function well during dark nights, astronomers need to preserve their night vision. They use red light because it does not disrupt their night vision as much as other colors of light. The very long exposure greatly enhances the faint light from the building and dome.