Glossarbegriffe: Spektrum

Redirected from Emissionslinie

Description: Ein Regenbogen entsteht, wenn Wassertröpfchen das Licht in die Spektralfarben Violett, Blau, Grün, Gelb, Orange und Rot zerlegen. Jede Farbe entspricht einem Bereich von Wellenlängen, und die Regenbogenfarben sind in der Reihenfolge zunehmender Wellenlänge von violett bis rot angeordnet. Diese Art von zerlegtem Licht oder allgemeiner von elektromagnetischer Strahlung nach Wellenlängen wird als Spektrum bezeichnet.

Elektromagnetische Strahlung ist eine Mischung aus Lichtteilchen, die "Photonen" genannt werden. Um ein Spektrum (beispielsweise von der Sonne oder von einem anderen astronomischen Objekt) zu erstellen, sortiert man die Photonen nach ihrer Energie und hält fest, wie viele Photonen es in jedem Energiebereich gibt. Nach einem Grundgesetz der Quantenmechanik ist dies gleichbedeutend mit der Sortierung des Lichts nach der Frequenz - eine weitere Möglichkeit, ein Spektrum zu erfassen.

Wenn die Energiemenge gleichmäßig mit der Wellenlänge (oder der Photonenenergie oder der Frequenz) variiert,
wird das Spektrum als kontinuierlich bezeichnet. Im Gegensatz dazu werden scharfe Einbrüche oder Spitzen in einem Spektrum bei bestimmten Wellenlängen als Absorptions- bzw. Emissionslinien bezeichnet. Solche Linien entstehen aufgrund von
Übergängen zwischen verschiedenen Energieniveaus innerhalb von Atomen oder Molekülen (oder sogar Atomkernen), die entweder Strahlung bei bestimmten Wellenlängen absorbieren oder emittieren. Im sichtbaren Licht zeigen Sterne beispielsweise kontinuierliche Spektren mit Absorptionslinien. Diese Linien geben Aufschluss über die chemische Zusammensetzung eines Sterns. Die Analyse von Spektren wird als Spektroskopie bezeichnet; Instrumente, die die Aufnahme von Spektren ermöglichen, werden Spektroskope, Spektrometer oder Spektrographen genannt.

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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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A composite showing four rainbows. Each is centred on different points

24 Hours of Rainbow

Bildunterschriften: This panoramic view taken with a smartphone of Livorno, Italy, showcases a series of vivid rainbows captured on three different days in December 2021. Rainbows are the result of sunlight being refracted by water droplets suspended in the air, typically after rainfall or during misty conditions. The water droplets act like a prism, breaking up (refracting) the sunlight into the various colours. The different wavelengths of light are refracted by different amounts, which is why we see this layering of colours. The photographer skillfully merged the most remarkable shots taken on different days to highlight the diverse sizes and brilliance of these rainbows. The locations at which the rainbows appear to be centred are different because each rainbow appeared when the Sun was at a different position in the sky. This composite image beautifully captures the transient yet mesmerising allure of rainbows, illustrating their fleeting appearance and gradual dissipation influenced by the shifting atmospheric conditions.
Bildnachweis: Fabrizio Guasconi/IAU OAE (CC BY 4.0)

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Related Diagrams

A smooth line declining at longer wavelengths with a few sharp dips.

Spectrum of an O-type star

Bildunterschriften: The spectrum of the O-type star HD 235673 with wavelength in nanometers on the x-axis and flux on the y-axis. The top part of the plot shows the same spectrum but with bright patches for wavelengths with high flux and dark patches for wavelengths with low flux. The colour of the line between 400 nm and 700 nm roughly corresponds to the colour the human eye would see light of that wavelength. Below 400 nm and above 700 nm, where the human eye can see little to no light, the lines are coloured blue and red respectively. The black lines show spectral absorption lines caused by atoms and ions of different elements in the star’s atmosphere. These atoms and ions absorb at specific wavelengths, causing sharp, dark lines in the spectra. How strong these lines are depends on the temperature of the star’s atmosphere. Two stars made from the same mix of elements could have spectra with vastly different sets of lines in their spectra if they have different temperatures in their atmospheres. For O-type stars the most important features are a small number of lines caused by ionized helium. These lines are stronger in O-type stars than in cooler stars. Lines from helium atoms and hydrogen atoms also appear in the spectrum. The spectrum has more flux at the blue end of the spectrum than at the red end of the spectrum.
Bildnachweis: IAU OAE/SDSS/Niall Deacon

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

Spectrum of a B-type star

Bildunterschriften: The spectrum of the B-type star HD 258982. The colour of the line between 400 nm and 700 nm roughly corresponds to the colour the human eye would see light of that wavelength. Below 400 nm and above 700 nm, where the human eye can see little to no light, the lines are coloured blue and red respectively. The black lines show spectral absorption lines caused by atoms and ions of different elements in the star’s atmosphere. These atoms and ions absorb at specific wavelengths, causing sharp, dark lines in the spectra. How strong these lines are depends on the temperature of the star’s atmosphere. Two stars made from the same mix of elements could have spectra with vastly different sets of lines in their spectra if they have different temperatures in their atmospheres. For B-type stars the most important lines are caused by helium atoms. These lines are strongest in B-type stars and weaker in hotter and cooler types. Lines from hydrogen atoms are also present but are not as strong as in cooler A-type stars.
Bildnachweis: IAU OAE/SDSS/Niall Deacon

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

A smooth line peaking about 420 nm then declining at longer wavelengths with a few fairly broad dips.

Spectrum of an A-type star

Bildunterschriften: The spectrum of the A-type star BD-11 1212. The colour of the line between 400 nm and 700 nm roughly corresponds to the colour the human eye would see light of that wavelength. Below 400 nm and above 700 nm, where the human eye can see little to no light, the lines are coloured blue and red respectively. The black lines show spectral absorption lines caused by atoms and ions of different elements in the star’s atmosphere. These atoms and ions absorb at specific wavelengths, causing sharp, dark lines in the spectra. How strong these lines are depends on the temperature of the star’s atmosphere. Two stars made from the same mix of elements could have spectra with vastly different sets of lines in their spectra if they have different temperatures in their atmospheres. Lines from hydrogen atoms dominate the spectra of A-type stars and are strongest at this spectral type.
Bildnachweis: IAU OAE/SDSS/Niall Deacon

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

A relatively smooth line peaking about 430 nm then declining at longer wavelengths with a few fairly broad dips.

Spectrum of an F-type star

Bildunterschriften: The spectrum of the F-type star 2MASS J22243289+4937443. The colour of the line between 400 nm and 700 nm roughly corresponds to the colour the human eye would see light of that wavelength. Below 400 nm and above 700 nm, where the human eye can see little to no light, the lines are coloured blue and red respectively. The black lines show spectral absorption lines caused by atoms and ions of different elements in the star’s atmosphere. These atoms and ions absorb at specific wavelengths, causing sharp, dark lines in the spectra. How strong these lines are depends on the temperature of the star’s atmosphere. Two stars made from the same mix of elements could have spectra with vastly different sets of lines in their spectra if they have different temperatures in their atmospheres. The lines from hydrogen atoms that are strongest in A-type stars are still relatively strong in F-type stars but lines from metals, particularly ionised calcium begin to become strong at this spectral type.
Bildnachweis: IAU OAE/SDSS/Niall Deacon

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

A quite ragged line peaking about 470 nm then declining at longer wavelengths with a few deeper dips.

Spectrum of a G-type star

Bildunterschriften: The spectrum of the G-type star UCAC4 700-069569. The colour of the line between 400 nm and 700 nm roughly corresponds to the colour the human eye would see light of that wavelength. Below 400 nm and above 700 nm, where the human eye can see little to no light, the lines are coloured blue and red respectively. The black lines show spectral absorption lines caused by atoms and ions of different elements in the star’s atmosphere. These atoms and ions absorb at specific wavelengths, causing sharp, dark lines in the spectra. How strong these lines are depends on the temperature of the star’s atmosphere. Two stars made from the same mix of elements could have spectra with vastly different sets of lines in their spectra if they have different temperatures in their atmospheres. In G-type stars lines from hydrogen atoms are weaker than in F-type stars and lines from ionised calcium stronger. Lines from metal atoms such as atoms of iron, sodium and calcium also begin to become prominent.
Bildnachweis: IAU OAE/SDSS/Niall Deacon

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

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