Caption: Winner in the 2022 IAU OAE Astrophotography Contest, category Still images of celestial patterns.   As Earth moves around the Sun, the positions of the stars in the night sky appear to change over the course of the year. This is well exemplified in this mosaic, with images taken in all four seasons throughout 2020 in the region of Veneto, Italy, showing the apparent motion of the Ursa Minor and Ursa Major constellations. Ursa Minor, the Little Bear, is a constellation of the northern hemisphere, and it contains the northern celestial pole, in our current epoch marked by a bright star called Polaris or the Pole Star. For centuries Polaris has been used for navigation in the northern hemisphere, as it has been almost at the exact pole position for roughly 200 years. In the Middle Ages and antiquity, there was no pole star; the celestial north pole lay in a dark region and the Greeks considered the “Little She-Bear” as a companion of the “Great She-Bear”, which is more easily recognizable. The brightest stars of these constellations were alternatively also considered as chariots by the Greeks, as written in Aratus’s famous didactic poem from the 3rd century before the common era. The most famous asterism in Ursa Major, composed of seven stars, has different names across the (northern) world. While considered as a chariot by the Greeks, it is “The Northern Dipper” in China, and “The Seven Oxen” for the ancient Romans. It was also the navigational purpose that led to the name The Great She-Bear, Ursa Major; for the Greeks, travelling towards the direction of the horizon above which Ursa Major appears meant moving towards the land of the bears (northern Europe). An animal is clearly recognizable when taking into account all the fainter stars in the vicinity of the seven bright ones. They considered it a female bear because Greek mythology connects this animal with the nymph Callisto, whose story describes the initiation rituals for women. In the top left, we see an image taken on a spring evening, while the image below shows the same portion of the sky on a summer evening. Going counterclockwise, we see the sky during autumn in the bottom right image, while the top right finally shows this portion of the sky in the winter. Note that the relative positions of Ursa Minor and the Big Dipper don’t change, but all stars appear to be moved in a circle around Polaris. This star pointing due north lies at the point where Earth’s rotational axis intersects the celestial sphere. The shift of constellations throughout the year is therefore a globe-clock or a globe-calendar, used by ancient civilizations to measure the year, and to predict the changes of seasons. It helps to establish, for instance, the best time for sowing and sailing as winds change with the seasons.
Credit: Giorgia Hofer/IAU OAE

Caption: 这张令人叹为观止的照片是 2020 年 6 月 25 日在印度尼西亚西爪哇库宁安省西里穆斯市凌加梅卡村的晴朗夜空下拍摄的，照片中的星轨掠过南半球的天际。星轨是地球自转所导致的恒星表观运动，当长时间跟踪时，就会产生这些令人着迷的光弧。因为这张照片是在赤道附近拍摄的，所以恒星所围绕旋转的点（南天极）靠近地平线。摄影师使用智能手机上的星轨功能，在较长时间内拍摄了一系列图像，并将它们叠加在一起。前景引人注目的大树增添了画面的深度，使上方天体的运动与地面的静止形成了鲜明对比，同时也遮掩了周围的一些光污染。世界不同地区的夜空景色各异，令人惊叹，使人们意识到保护各地黑暗天空的重要性。
Credit: Slamat Riyadi/IAU OAE (CC BY 4.0)

Caption: This video shows the Milky Way’s sprawling brilliance across the celestial expanse. Among the stars’ grand theatre, the Southern Cross constellation claims its place in the scene, distinguished by its distinctive cross shape as seen in the top of this video and slightly to the right just over the Milky Way, slowly disappearing as the video progresses. This celestial marker, a prominent feature in the southern hemisphere, holds cultural and navigational significance, having served as a navigational guidepost for centuries. Accompanying the Milky Way’s grandeur are the two Magellanic clouds, celestial companions seen dancing in the distant sky. The Carina Nebula adds its ethereal glow to the cosmic panorama, painting a radiant hue against the darkness. In the midst of this celestial ballet, a gentle green hue envelops the atmosphere, a phenomenon known as airglow, adding a touch of subtle luminescence to the night sky. The terrestrial also makes an appearance, with planes flying overhead and vehicles driving between observatory buildings. This time-lapse, taken from the La Silla Observatory in Chile, is a window to the captivating dance of stars, offering a glimpse into the awe-inspiring beauty of our galaxy and the celestial landmarks that grace the southern sky.
Credit: José Rodrigues/IAU OAE (CC BY 4.0)

Caption: Taken from San Pedro de Atacama, Chile, in June 2023, this time-lapse reveals the celestial ballet that unfolds as the Southern Cross takes its majestic journey across the sky, pointing the way to the South Celestial Pole around which the sky rotates, until it gracefully sets. The star-studded canvas showcases the grandeur of the Milky Way, adorned by the rotating Large and Small Magellanic Clouds swirling around the Southern Celestial Pole. The prominent constellations of Crux, Centaurus, Scorpius, and the former Argo Navis (Carina, Puppis, Vela) are also visible. The spectacle begins just after nightfall, capturing the radiant descent of Canopus, a beacon about to dip below the horizon. Throughout the sequence, there is a subtle presence of passing aeroplanes, fleeting headlights of cars, drifting clouds, and the ethereal airglow. At a stunning moment, a vivid meteor streaked across the sky, a breathtaking fireball briefly igniting the right lower corner around the 41st second mark. As the sequence progresses, the rising moon elegantly illuminates the landscape, casting its glow upon an ancient tree trunk resting on the dry, dusty grounds of the Salar de Atacama. This captivating journey through the night skies concludes before the break of dawn, offering a glimpse into the celestial marvels that are woven into the nocturnal tapestry of San Pedro de Atacama.
Credit: Uwe Reichert/IAU OAE (CC BY 4.0)

Caption: This time-lapse captures the movement of the stars alongside the majestic 64-metre Sardinia Radio Telescope (SRT) from the National Institute of Astrophysics (INAF), with special attention to the renowned Big Dipper against the backdrop of the celestial sphere. The camera pans as the famous asterism sinks in the sky while planes fly past and the radio telescope rotates. The harmonious interplay between the stellar pathways and the colossal dish of the radio telescope creates a mesmerising visual ode to the cosmic ballet taken in September 2019.
Credit: Antonio Finazzi/IAU OAE (CC BY 4.0)

Caption: 这张拍摄于2022年10月的照片是在印度阿马尔提亚村（Amartiya）帕诺提耶（Panotiya）的黑夜中拍摄的，展现了夜空中美丽的星轨。摄影师仅用一部智能手机和一个三脚架就捕捉到了这些星轨——它们是我们星球自转的视觉证据，因为每一条星轨都代表着地球自转时恒星的明显运动，创造出令人着迷的宇宙光影编舞。恒星有不同的颜色，有的闪着蓝光，有的泛白，暗示着它们不同的温度和组成。此外，一架飞机的细微轨迹与永恒的星空之舞短暂的交汇在一起，宁静的星空与下方熙熙攘攘的生命活动形成了鲜明对比。
Credit: Govind Gurjar/IAU OAE (CC BY 4.0)

Caption: The Big Dipper asterism gracefully moves above the otherworldly tufa formations of Mono Lake, California. The time-lapse captures the Big Dipper’s movement across the northern horizon until its inferior conjunction. At Mono Lake’s latitude (+38°), the stars of the Big Dipper remain circumpolar, except for Alkaid. The North Star sits 38° above the horizon, just outside the field of view in the top right. The lunar illumination bathes the landscape in a soft glow, gradually fading as the Moon sets, cloaking the scene in darkness.
Credit: Fabrizio Melandri/IAU OAE (CC BY 4.0)

Caption: A cosmic journey unfolds across continents in this time-lapse video which captures both iconic constellations from diverse corners of the world. Starting in China, the Big Dipper graces the night sky, a steadfast guide embedded in cultural narratives. Its luminance marks the beginning of this celestial odyssey. The two pointer stars on the end of the Big Dipper point to the North Star (Polaris) which appears to remain stationary as the sky rotates. From Nepal’s lofty peaks, the Big Dipper’s familiarity persists, a reliable fixture in the shifting panorama of the rotating planet. Moving to Chile, the Southern Cross adorns the firmament, emblematic of the southern skies. Frames from Chile showcase this constellation accompanied by the Milky Way Galaxy. In Namibia, a telescope from the H.E.S.S. Observatory appears in the video. Later, nestled beneath sheltering trees, the Big Dipper persists in its celestial prominence, appearing against a canvas of stars. Using varied techniques — fisheye lenses, static cameras, and Earth's movement-tracking — each frame unveils the Cross’s grandeur against diverse landscapes. These sequences — marked by star trails and Earth’s rotation—highlight the enduring presence of the Big Dipper and Southern Cross, bridging cultures and celestial beauty across hemispheres.
Credit: Jianfeng Dai/IAU OAE (CC BY 4.0)