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Glossarbegriffe: Stellare Aktivität

Also known as Sternaktivität

Description: "Aktivität" ist ein Sammelbegriff für die verschiedenen Auswirkungen, die Magnetfelder auf Sterne haben. Sterne mit starken Magnetfeldern haben mehr Sternflecken auf ihrer Oberfläche. Stellare Magnetfelder sind wahrscheinlich auch die Wärmequelle für die Korona eines Sterns, sodass Sterne mit starken Magnetfeldern mehr Röntgen- und Ultraviolettstrahlung aus ihrer Korona aufweisen. Die Aktivität lässt sich auch im Spektrum des Sterns erkennen, insbesondere in der Emission der H-alpha-Linie (einer Spektrallinie von angeregtem Wasserstoff). Zusammengenommen quantifizieren diese Effekte grob die "Aktivität" eines Sterns. Massereiche Sterne (mit dem Spektraltyp O, B und frühes A) haben in der Regel eine geringe Aktivität. Die Aktivität nimmt bei Sternen mit geringerer Masse zu und erreicht ihren Höhepunkt bei Roten Zwergen (M-Zwergen). Junge Sterne sind aktiver als alte Sterne. Die Sonne folgt einem Aktivitätszyklus von 11 Jahren, der sich in einer unterschiedlichen Anzahl von Sonnenflecken niederschlägt (Sonnenfleckenzyklus).

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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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Image showing groups of sunspots as dark patches which lie in bands above and below the Sun's equator

Sunspots

Bildunterschriften: In this image the sun peppered with groups of sunspots over almost nine days between July and August 2012. The sunspots seen in this image have been sources of the solar flares and coronal mass ejections (CME). In this image particulary, the sun is approaching solar maximum in its cycle (solar cycle), where we see many spots forming along the suns' equator. These sunspots and activity are seen in the southern hemisphere, before then most of the activity was on the northern hemisphere.
Bildnachweis: NASA/SDO/HMI credit link

License: PD Public Domain icons


The Sun in ultraviolet appears as a circle. The flare is a bright patch in the upper right 3/4 of the way from the center

Solar flare

Bildunterschriften: This image shows the mid-level solar flare that was observed in March 2022 by the Solar Dynamic Observatory (SDO). The SDO observes the Sun activity, hence it shows the regions on the Sun where there is activity. A solar flare is brief brightening on the sun's surface, this particular flare is an M-class, which means that it is a tenth of the size of the most intense flares, namely the X-flares. Solar flares are barely visible with the naked eye, thus the SDO. The image here, is captured in extreme ultravoilet light that was colourized by red in the SDO, the flare appears in the upper of the solar disk.
Bildnachweis: NASA/SDO credit link

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