Glossarbegriffe: O-Stern

Also known as Stern der Spektralklasse O oder Stern des Spektraltyps O

Description: Ein Stern mit der Spektralklasse "O". Astronomen erkennen Sterne vom Spektraltyp O daran, dass in ihren Spektren Absorptionslinien von ionisiertem Helium zu sehen sind. Sie haben typische (effektive) Temperaturen zwischen etwa 10.000 Kelvin (K) und 30.000 K. Im Vergleich zu anderen Sternen erscheinen sie dem menschlichen Auge bläulich-weiß, außer Extinktionseffekte (entweder durch die Erdatmosphäre oder durch das interstellare Medium) spielen eine Rolle. Sterne vom Typ O sind die heißesten und blauesten Sterne auf der Hauptreihe im Hertzsprung-Russell-Diagramm. O-Sterne auf der Hauptreihe haben die höchsten Massen (mehr als 15 Sonnenmassen) und die kürzeste Lebensdauer beim Wasserstoffbrennen und sind daher meist in und um Sternentstehungsgebiete zu finden.

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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".

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

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