La Silla gets the green light
The magical green glow that dominates the sky in this Picture of the Week is airglow. You won’t be able to see it with the naked eye, but sensitive cameras can capture this faint light emitted by the Earth’s atmosphere, though only in the darkest of places. It reveals itself where there is little light pollution, like here at ESO’s La Silla Observatory, on the outskirts of the Chilean Atacama Desert.
With its green colour, the airglow’s continuous presence in the sky is not to be confused with the dynamic, dancing auroras. Airglow is a chemical process triggered by ultraviolet radiation from the Sun, which causes atoms in the upper atmosphere to emit very faint light. Auroras, on the other hand, are caused by charged particles catapulted into the Earth’s magnetic field. And while auroras are elusive and short-lived spectacles, airglow is more like quiet background music. The green glow here is caused by oxygen atoms, but it can also be red or yellow, depending on the type of atoms or molecules that cause them.
But there is more than just airglow hiding in this fisheye view of La Silla. Can you spot the three telescopes? ESO’s 3.6m telescope, at the bottom, is the one seemingly puffing the Milky Way like smoke. The Swiss 1.2-metre Leonhard Euler Telescope (top left) is also pretty easy to find, but the almost unrecognisable New Technology Telescope might be more of a challenge to find (it’s hiding at the top).
Now that you found the telescopes, how about seeing them up close? Yes, you can actually visit them. There will be no airglow, as visits are during daytime to avoid interfering with the night-time work, and airglow is invisible to the naked eye –– but the telescopes more than make up for it.
Alternative projections of this image
Credit:J. Pérez/ESO
About the Image
| Id: | potw2514a |
| Type: | Photographic |
| Release date: | 7 April 2025, 06:00 |
| Size: | 7418 x 7418 px |
About the Object
| Name: | La Silla, Milky Way |
| Type: | Unspecified : Sky Phenomenon : Night Sky : Milky Way Unspecified : Sky Phenomenon : Night Sky : Night glow Unspecified : Technology : Observatory |
| Category: | La Silla |
Image Formats
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