A mysterious green glow lighting up the night sky over Chile's Atacama Desert is not an aurora, but a natural atmospheric phenomenon known as "airglow." Captured by the La Silla Observatory camera, operated by the European Southern Observatory (ESO), this extraordinary event occurs in the light-pollution-free region of the desert.
While airglow may be confused with auroras, the two phenomena are different. Airglow is a faint, continuous light emitted when ultraviolet rays from the Sun excite atoms and molecules in the atmosphere. In contrast, auroras are brighter and more temporary light displays caused by charged particles from the Sun interacting with Earth's magnetic field.
Airglow is typically too faint to be seen by the naked eye and can only be detected by high-precision cameras in dark locations. The green color is usually produced by oxygen atoms releasing energy. Sometimes, it can also appear in red or yellow hues.
The image captured at La Silla also shows three telescopes. The ESO's 3.6-meter telescope is positioned beautifully, giving the Milky Way a smoky appearance. The Swiss Leonhard Euler 1.2-meter telescope is clearly visible in the upper left, while the New Technology Telescope is hidden in the upper portion of the image.
La Silla Observatory is open for visits during the day, but due to its nighttime research schedule, visits are restricted to daylight hours. Though airglow cannot be seen with the naked eye, visitors can explore the telescopes up close.
