Glossarbegriffe: M-Stern

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

Description: Ein Stern mit der Spektralklasse "M". Astronomen erkennen M-Sterne an molekularen Absorptionslinien in ihren Spektren, vor allem von Titanoxid. Sie haben typische (effektive) Temperaturen zwischen etwa 2500 Kelvin (K) und 3700 K. Im Vergleich zu anderen Sternen erscheinen sie dem menschlichen Auge rot. Hauptreihensterne mit dem Spektraltyp M werden als Rote Zwerge bezeichnet. Sterne des Spektraltyps M können aber auch Rote Riesen oder Rote Überriesen sein. Rote Riesen oder Rote Überriesen sind hauptsächlich M-Sterne, können aber auch K-Sterne sein, oder zu exotischeren Spektralklassen mit starken Kohlenstofflinien gehören. Beteigeuze im Sternbild Orion ist ein Überriese vom Typ M.

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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 choppy line increasing at longer wavelengths with large wide dips and a few sharper dips.

Spectrum of an M-type star

Bildunterschriften: The spectrum of the M-type star 2MASS J15581272+8457104. 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, ions and molecules of different elements in the star’s atmosphere. These atoms, ions and molecules 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 atmospheres of M-type stars are cool enough for some chemical compounds to form. These are often referred to as molecules in astronomy, even if they are not strictly molecules in chemistry. These molecules produce so many lines in an M-type star’s spectrum that the lines appear to merge together in huge bands that remove large chunks from the spectrum. In M-type stars, titanium oxide has a large number of these bands in visible light, dominating huge regions of the spectrum.
Bildnachweis: IAU OAE/SDSS/Niall Deacon

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