A recent study analyses data collected at 44 of the darkest places in the world, including the Canary Island Observatories, to develop the first complete reference method to measure the natural brightness of the night sky using low-cost photometers.
A recent study analyses data collected at 44 of the darkest places in the world, including the Canary Island Observatories, to develop the first complete reference method to measure the natural brightness of the night sky using low-cost photometers.
Of the 44 photometers in the survey, the Roque de los Muchachos Observatory (Garafía, La Palma, Canary Islands) stands out at the darkest of all the skies analysed.
The night sky is not completely dark; even in the remotest places there is a glow in the sky produced by natural components, both terrestrial and extraterrestrial, and by artificial lighting of human origin. Even though the main bright sources such as the Moon, the Milky Way, and the Zodiacal light are easily recognisable, there is a glow which dominates the sky brightness on the darkest nights, produced in the upper layers of the atmosphere, and whose strength depends on a set of complex factors such as the time of year, the geographical location, and the solar cycle.
Solar Cycles are ordered in periods of activity lasting 11 years. We refer to solar maximum when the activity of the Sun has grown, sunspots appear on its surface, and its radiative emission has grown, which affects the molecules in the Earth’s atmosphere, causing an increase in the brightness of the night sky. When these events are much reduced we call this solar minimum.
Read more at Instituto de Astrofísica de Canarias (IAC)
Image: In the upper part of the image, the Observatory of the Roque de los Muchachos Observatory (Garafía, La Palma, Canary Islands) taken in February 2020. The lower part shows the sky in the southern hemisphere from the La Silla Observatory (ESO, Chile) in April 2016. In this composition the Milky Way runs almost vertically above and below the horizon. In the upper half Venus is immersed in the Zodiacal Light, which produces a complete circle through the starry sky. Andromeda and the Magellanic Clouds can also be seen. This image, produced by astrophotographers Juan Carlos Casado and Petr Horálek, was Astronomy Picture of the Day (APOD) on February 27th 2020 (apod.nasa.gov/apod/ap200227.html) (Credit: Juan Carlos Casado and Petr Horálek)
