When Northern Heaven Meets Southern

Seeing this photo we may feel a little confused! This Photograph of the Week captures both the Northern and Southern Hemispheres at the same time — the entire night sky in a single image — something that would be impossible to observe in real life.

To create this image, photographers Petr Horálek and Juan Carlos Casado took two photographs in observatories located in the same latitudes but in different hemispheres. The top half of the image was taken at the Instituto de Astrophysics de Canarias’ Roque de los Muchachos Observatory, in La Palma in the Canary Islands, 29º north of the equator, while the bottom half was taken at ESO’s La Silla Observatory in the Chilean desert from Atacama, 29º south of the equator. When digitally combined, the two images create a continuous sweeping view of the night sky.

One of the most notable structures in the image is the whitish glowing streak that runs vertically from the center, up and down. It is the zodiacal light, a phenomenon caused by the dust that permeates our Solar System by scattering sunlight, which is only visible in regions with extremely dark skies, free from light pollution. We can still see the planet Venus shining brightly in the zodiacal light beam of the Northern Hemisphere.

In the lower image we can see several La Silla telescopes, with ESO’s 1-meter Schmidt telescope in the foreground. The reflecting mirror that appears upside down in the upper image is part of the Cherenkov Telescope Array (CTA), a group of gamma-ray telescopes that observe some of the most energetic phenomena in the Universe. A second group of these telescopes will be installed in the Southern Hemisphere, close to ESO’s Paranal Observatory, through an agreement between the CTA Observatory and ESO.