This is what the stars look like from the Moon captured by NASA astronauts

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Humanity evolved over millions of years to adapt to life on Earth. Learning patterns in his surroundings in order to survive. However, common sense and many things taken for granted lose, to a certain extent, their validity in the lunar environment. Since then, numerous people have expressed confusion over the thousands of photographs and images obtained by probes or the Apollo missions. One of the biggest questions is the absence of stars in the dark sky.

Group of stars observed during the Apollo 16 mission. Credits: NASA.

Writing with light

The Earth has an atmosphere composed mainly of nitrogen and oxygen. These gases are responsible for diffracting sunlight and giving it its characteristic bluish hue. In addition, it poses certain problems when studying the universe at some wavelengths. On the other hand, andn the Moon is in a practically perfect vacuum, showing a dark sky and an excellent opportunity to observe stars, nebulae and galaxies with as little pollution as possible.

Additionally, when exploring the surface and taking photographs, the brightness of the Sun reflected off the lunar soil and the narrow dynamic range of the cameras, it becomes very difficult to observe the stars. Similar to trying to do astrophotography from inside a fully lit stadium. Even if the sky is clear, the faint stars will be overshadowed by the intense brightness of the reflectors.

The first interplanetary telescope

The Moon offers an incredible opportunity to make astronomical observations. For this reason, in the Apollo 16 mission the NASA decided to send a telescope to study stars, nebulae, the solar wind and the Earth at far ultraviolet wavelengths. It also had a camera to record on film the images captured during the stay on the surface to be recovered and analyzed in the laboratories.

The far-ultraviolet spectrograph/camera deployed in the shadow of the lunar module and illuminated by light reflected from the lunar regolith. Credits: NASA.

Weighing 22 kilograms, the telescope had a camera and a spectrograph. In the first case, he was able to observe between 105 to 126 and 120 to 155 micrometers, while the second did so between 300 and 1350 angstroms. It was deployed in the shadow of the lunar module to eliminate the Sun's glare. It was manually aimed by John Young and the targets were determined weeks in advance. In 1972 it became the first essentially interplanetary astronomical observation station.

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False color photograph of the Large Magellanic Cloud observed in ultraviolet. Credits: NASA.

Rediscovering the Earth

One of the most interesting objectives was to be able to study the planet in the far ultraviolet. Something that to date had not been achieved from such a distance. Incredible images of the geocorona, ionosphere, auroras and atmospheric glow were obtained.

The outermost layers of the Earth's atmosphere are the geocorona, composed of neutral hydrogen, and the ionosphere, corresponding to gases ionized by solar radiation.

The geocorona corresponds to a large area of low hydrogen density. Credits: NASA.
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False color image of the Earth seen in ultraviolet. While the daytime side reflects light very efficiently, on the nightside it is possible to observe emissions by charged particles in the auroras. As well as the presence of numerous stars in the background. Credits: NASA.

Stars from the Moon

A total of 178 frames were extracted during the third and final spacewalk. In total, 11 targets were searched, including nebulae, star clusters and the Large Magellanic Cloud. All images were digitized and can be found in their original state at the WikiArchives.Space file.

Group of stars observed during the Apollo 16 mission. Credits: NASA.

A similar modified version of the telescope would be used on the Skylab space station, for the purpose of continuing observations of the solar wind and comets.

Francisco Andrés Forero Daza