A Koi-smic fish

This Picture of the Week shows the brightly coloured Gum 3 nebula as seen with the VLT Survey Telescope (VST), hosted at ESO’s Paranal Observatory in the Chilean Atacama Desert. Attentive viewers may find that part of Gum 3 resembles a Koi fish in this VST image. Equipped with the OmegaCAM instrument, an enormous 268-megapixel camera, the telescope is designed to survey large areas of the southern sky in visible light and take stunning images like this one.

Gum 3 is an interstellar cloud of gas and dust located about 3600 light-years away, between the Monoceros and Canis Major constellations. It is named after Colin Stanley Gum, an Australian astronomer who catalogued 84 nebulae in the southern sky. 

When the intense ultraviolet radiation from nearby young stars hits hydrogen atoms in the cloud, they emit visible light at very specific colours, which we see as shades of red and pink in the image. At the same time, tiny particles of dust within the cloud reflect starlight, especially blue colours, similar to what makes the sky look blue here on Earth. This play of colours makes nebulae like this spectacular to look at.

This image shows not only colour, but also the lack of it. Look closely at the area just right of the brightest part of the cloud  — right of the pink “Koi-smic fish”. Does anything look odd to you? It’s not that there really are fewer stars in this dark area; instead, there is a big clump of dust that blocks part of the visible light, hiding the stars from VST and us.

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• Explore this nebula in more detail in this video.