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Glossarbegriffe: Tagundnachtgleiche

Also known as Äquinoktium

Description: Das wahre Äquinoktium ist der Zeitpunkt, an dem die Sonne auf ihrer jährlichen Reise durch die Ekliptik den Himmelsäquator überquert. Das Wort leitet sich vom lateinischen aequinoctium ab, mit aequus (gleich) und nox (Genitiv noctis) (Nacht). Am Tag der Tagundnachtgleiche (auch Äquinoktium genannt) sind die Tages- und Nachtzeiten auf der ganzen Erde ungefähr gleich lang, nicht nur in Äquatornähe. Für einen Beobachter auf der Erde geht die Sonne genau in der östlichen Himmelsrichtung auf, bewegt sich an diesem Tag scheinbar entlang der Linie des Himmelsäquators und geht genau im Westen unter. Es gibt zwei Tagundnachtgleichen pro Jahr, eine um den 20. März und eine um den 23. September. Die März-Tagundnachtgleiche zeigt den scheinbaren Durchgang der Sonne in Richtung der nördlichen Hemisphäre an, die September-Tagundnachtgleiche den scheinbaren Durchgang der Sonne in Richtung Süden.

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Term and definition status: The original definition of this term in English have been approved by a research astronomer and a teacher
The translation of this term and its definition is still awaiting approval

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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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

Bildunterschriften: 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.
Bildnachweis: John Paul Pile/IAU OAE (CC BY 4.0)

License: CC-BY-4.0 Creative Commons Namensnennung 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

Bildunterschriften: 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.
Bildnachweis: Frank Niessen/IAU OAE (CC BY 4.0)

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


Fischaugenaufnahme dreier Bahnen der Sonne über den Himmel. Die höchste kreuzt fast die Bildmitte, die niedrigste erreicht nur ein Sechstel des Weges

Sonnenwende und Tagundnachtgleiche

Bildunterschriften: Dieses Bild verdeutlicht den Tagbogen der Sonne am Himmel während der Wintersonnenwende (unten), der Tagundnachtgleiche (Mitte) und der Sommersonnenwende (oben) und wurde zwischen dem 21. Dezember 2007 und dem 20. Juni 2008 in Bursa in der Türkei aufgenommen. Mit einem Fischaugenobjektiv hat der Fotograf die Positionen der Sonne in regelmäßigen Abständen von Sonnenaufgang bis Sonnenuntergang an den drei Tagen eingefangen, um die wechselnden Längen von Tag und Nacht im Laufe des Jahres zu veranschaulichen. Die Veränderungen der täglichen Bahn der Sonne über den Himmel, ihre Höhe zur Mittagszeit, die Positionen von Sonnenauf- und -untergang sowie die Länge eines Tages ergeben sich aus der Neigung der Erdachse relativ zu ihrer Umlaufbahn um die Sonne. Die Bilderserie wurde von einem Dach in Bursa aus aufgenommen und die Landschaft fügt dem Ganzen seine eigene Note hinzu, indem sie hier und da den Horizont verdeckt. Sie stellt in gewisser Weise ein Tagebuch dar, das eine eindrucksvolle Darstellung des Anblicks der Sonnenbahn von mittleren nördlichen Breitengraden aus bietet. Norden ist oben und Süden unten.
Bildnachweis: Tunç Tezel/IAU OAE (CC BY 4.0)

License: CC-BY-4.0 Creative Commons Namensnennung 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

Bildunterschriften: 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.
Bildnachweis: Marcella Giulia Pace/IAU OAE (CC BY 4.0)

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

Related Diagrams


Pisces appears as a SW-pointing v-shape with loops at the end of each line. The ecliptic runs WSW to ENE through Pisces.

Pisces Constellation Map

Bildunterschriften: The constellation Pisces along with its bright stars and surrounding constellations. Pisces is surrounded by (going clockwise from the top) Andromeda, Pegasus, Aquarius, Cetus, Aries and Triangulum. Pisces lies on the ecliptic (shown here as a blue line), this is the path the Sun appears to take across the sky over the course of a year. The Sun is in Pisces from mid March to mid April. Thus the Sun is in Pisces at the March equinox. At this point the ecliptic crosses the celestial equator. The Sun’s location at the spring equinox is used to set the zero point of the Right Ascension positional coordinate. The other planets of the Solar System can often be found in Pisces. Pisces spans the celestial equator and is thus visible at some time in the year from all of planet Earth. In the most arctic or antarctic regions of the world, some parts of the constellation may not be visible. Pisces is most visible in the evenings in the northern hemisphere autumn and southern hemisphere spring The grand design spiral galaxy M74 is marked on this diagram with a small red circle. The y-axis of this diagram is in degrees of declination and with north as up and the x-axis is in hours of right ascension with east to the left. The sizes of the stars marked here relate to the star's apparent magnitude, a measure of its apparent brightness. The larger dots represent brighter stars. The Greek letters mark the brightest stars in the constellation. These are ranked by brightness with the brightest star being labeled alpha, the second brightest beta, etc., although this ordering is not always followed exactly. The dotted boundary lines mark the IAU's boundaries of the constellations and the solid green lines mark one of the common forms used to represent the figures of the constellations. Neither the constellation boundaries, nor the lines joining the stars appear on the sky.
Bildnachweis: Adapted by the IAU Office of Astronomy for Education from the original by IAU/Sky & Telescope

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