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Glossary term: Sun Path (Day Arc)

Description: The Sun's path or day arc traces the apparent motion of the Sun in the sky, as seen by an observer at a fixed position on Earth. Each day, the path traces out an arc, starting with sunrise in the eastern part of the sky and ending with sunset in the western part. Only at the spring and autumn equinoxes does the Sun rise exactly due east and set exactly due west. At the winter solstice, the arc is shortest and lowest in the sky. From then on, the length of that arc, and with it the length of the day, increases, and each successive arc is higher in the sky than the day before, reaching maximum height, and maximum day length, at the summer solstice. This process then repeats in the opposite order, again reaching the shortest, lowest arc at winter solstice.

North of the Arctic Circle and south of the Antarctic Circle the Sun does not rise for extended periods in winter or set for extended periods in summer. Hence, they can have nights that last several months in the winter and days that last several months in the summer. During one of these polar days the Sun travels around the sky in a circle, moving from a high point at midday to a low point at midnight without ever crossing the horizon.

The set of solar arcs can be captured in a long-term exposure image called a solargraph.

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Term and definition status: This term and its definition have been approved by a research astronomer and a teacher

The OAE Multilingual Glossary is a project of the IAU Office of Astronomy for Education (OAE) in collaboration with the IAU Office of Astronomy Outreach (OAO). The terms and definitions were chosen, written and reviewed by a collective effort from the OAE, the OAE Centers and Nodes, the OAE National Astronomy Education Coordinators (NAECs) and other volunteers. You can find a full list of credits here. All glossary terms and their definitions are released under a Creative Commons CC BY-4.0 license and should be credited to "IAU OAE".

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The Sun sinks from the top left of the image towards the middle. This path is reflected in the surface of the lake.

The Last Hour of the Day

Caption: This image, taken on 2 May 1997 at Lake Scaffaiolo in Italy, masterfully captures the Sun's descent in a sequence of mirrored reflections on the placid waters. Its breathtaking representation of time showcases the serene beauty of the surroundings, and stands as a timeless testament to the fleeting moments of the day’s final hour.
Credit: Fabrizio Melandri/IAU OAE (CC BY 4.0)

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons


12 images of sunset. Sunset moves from the left at the top, to the right in the middle, and back to the left at the bottom

Where the Sun Sets Every Month

Caption: Taken with a smartphone from San Rafael, Bulacan, Philippines, this series of images capture the changing position of sunset over the year owing to Earth’s axial tilt and orbit around the Sun. From January to December 2022, each image reflects the changing backdrop and position of the Sun at dusk. Observe the changing foliage and the appearance of an electricity pole in October. This collection serves as a visual testament to the celestial dance between Earth and the Sun, and the natural transformations on the ground.
Credit: John Paul Pile/IAU OAE (CC BY 4.0)

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons


24 images of the Sun around the edge of a circular image. In the lowest image, a black circle blocks the centre of the Sun.

The Eclipse Clock-Eclipse on a Polar Day

Caption: Constructed by combining multiple images over the course of a 24-hour period, the image was captured in Union Glacier, Antarctica, during the total solar eclipse of 4 December 2021, and showcases the day arc of the Sun. It illustrates the unique phenomenon of a polar day, during which the Sun travels around the sky without setting. During polar days, areas within the polar circles experience 24 hours of continuous daylight, and the Sun doesn’t set for an extended period. The image also offers a rare perspective of a solar eclipse, where the Moon passes between the Sun and Earth, and as viewed from Earth. This can be seen in the lower image of the Sun, where the Moon covers the solar disc.
Credit: Stephanie Ziyi Ye/IAU OAE (CC BY 4.0)

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons


Seven images of the Sun. From the left it sinks, reaching its lowest in the centre image, before rising higher to the right.

When the Sun Bounces

Caption: This image was taken at Norway's North Cape. Owing to the latitude of this location, the Sun never truly sets during the summer months, from around April to August. This results in the unique spectacle of continuous daylight, known as a polar day. This captivating series of images, taken in 2022, showcases the Sun's relentless journey across the horizon every 30 minutes. At its lowest point in the sky, the Sun does not set, but appears to bounce off the horizon. The globe on the far right in the photo stands as a sentinel, marking the northernmost point of the European continental mainland.
Credit: Milos Obert/IAU OAE (CC BY 4.0)

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons


Curved bright lines rise from the left, peaking on the right. The further to the left a line rises, the higher it peaks.

The Path of the Sun

Caption: This enchanting image, captured in Germany between 21 June 2018 and 21 December 2018, is a poetic blend of art and science, showcasing nature's rhythm and the passage of time. It combines images taken at different times of day over the course of six months. Each curve tracks the Sun’s path (or arc) across the sky on a particular day. The sweeping arc of the Sun is distorted here by the projection, making it appear like a curve. The position of the daily arc across the sky changes with the Sun’s seasonal movement in the sky. Captured using a simple pinhole camera fashioned from a coffee can, it shows the Sun's journey over the course of six months, and the gradual shift of the daily arc from the summer, when it is higher in the sky, to its lowest arc at the winter solstice. Gaps in the Sun’s path represent days or times of day when the Sun was obscured by clouds. This image is a vivid testament to the changing seasons, revealing the Sun's dance in the sky as days grow shorter or longer.
Credit: Frank Niessen/IAU OAE (CC BY 4.0)

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons


Three paths of the Sun across the sky. The highest almost crosses the middle of the image, the lowest is one sixth of the way

Solstices and Equinox

Caption: This captivating image showcases the journey of the Sun through the sky during the winter solstice (bottom), equinox (middle), and summer solstice (top) in Bursa, Turkey, between 21 December 2007 and 20 June 2008. Using a fisheye lens, the photographer captured the Sun's positions at regular intervals from sunrise to sunset on the three different days, illustrating the changing lengths of day and night throughout the year. The variations in the Sun’s daily path across the sky, its height at midday, and the positions of sunrise and sunset, as well as the length of a day, depend on Earth’s axial tilt relative to its orbit around the Sun. The series was taken from a rooftop in Bursa, where the local terrain adds its own unique touch by occasionally obstructing the horizon. Oriented with north at the top and south at the bottom, this visual diary serves as a stunning representation of the Sun’s path for those residing in mid-northern latitudes.
Credit: Tunç Tezel/IAU OAE (CC BY 4.0)

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons


Many images of the sunset in a montage. The Sun’s setting position changes from the left in winter to the right in summer.

Occasive Amplitude

Caption: Captured from Gatto Corvino village in Sicily, this composite showcases the Sun setting at various points over the sea from the winter to the summer solstice (2016–2017). The centre frame marks due west. As Earth orbits the Sun, the position of the setting (and rising) Sun changes from being northward of due west (east) in summer to southward of due west (east) in winter. During the equinoxes — when day and night are of equal length — the Sun rises directly in the east and sets directly in the west. The changing location of the Sun on the horizon is due to Earth’s axial tilt as it orbits the Sun. In temperate regions of Earth, the Sun’s height above the horizon at noon is at its highest and lowest points in the sky on the summer and winter solstices respectively.
Credit: Marcella Giulia Pace/IAU OAE (CC BY 4.0)

License: CC-BY-4.0 Creative Commons Attribution 4.0 International (CC BY 4.0) icons

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