The Milky Way Across the Zenith

Winner in the 2022 IAU OAE Astrophotography Contest, category Still images of celestial patterns. This all-sky image shows our home galaxy, the Milky Way, crossing the zenith, the point just above the observer as seen from Nagano, Japan, in May 2019. Such images of the whole sky can be taken either with a fish-eye lens or with a convex mirror on the ground, the latter of which would show the photographer as well. Some of the brightest stars in the night sky can be seen in this image, as well as two of the giant planets of our Solar System: Jupiter, the brightest point in the bottom of this image, and Saturn, another bright point just to the opposite side of the Galaxy, to the bottom and next to the horizon. Directly right of the Milky Way and below Jupiter, we can spot the bright red star Antares, the primary star of the Japanese asterism of The Heart. Japanese constellations derive from ancient Chinese constellations, which were adopted with only slight or no changes. In this tradition, The Heart is the heart of the “Azure Dragon”, a super-constellation that represents the spring. In the Babylonian and Greco-Roman traditions, this area is considered the heart of the Scorpion. In Babylonian religion, the star is associated with Lisi, the child of the mother goddess, but in Greek mythology it is related to the planet Mars, because of its colour. The reddish colour also led to the star’s Chinese name “The Fire Star”. We know that this colour is caused by its relatively cool temperature. Going from Antares to the right of the image, we find the more northern parts of the sky. The bright star in the lower-right of the image, close to the horizon, is Arcturus, located in the modern constellation Boötes. While Antares and its surrounding area are considered the heart of the Azure Dragon, Arcturus and Spica (below the horizon) are two single-star asterisms forming its huge horn. Pointing towards it from above, at the right-hand edge of the image’s horizon, we can see the handle of the Big Dipper, or Plough, which is part of the constellation Ursa Major. The bright point to the right of the galaxy and just above the middle of the image is Vega, located in the modern constellation Lyra. Extending a line to the other side of the Galaxy and a bit lower in the image we can find Altair, in the constellation Aquila. From that point we extend another line to Deneb, the brightest star in the constellation of the Swan, also a bit higher in this image and completely flooded by the Milky Way. These three bright stars comprise the asterism known as the Summer Triangle in the northern hemisphere. Credit: Ohnishi Kouji/IAU OAE (CC BY 4.0