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Glossary term: כוכב מסוג A

Also known as כוכב

Description: כוכב מסוג ספקטרלי "A". אסטרונומים מזהים כוכבים מסוג A על ידי נוכחות קווי ספיגה חזקים של מימן בספקטרום שלהם. הטמפרטורה האופיינית (האפקטיבית) שלהם נעה בין 7400 קלווין (K) ל-10,000 K. בהשוואה לכוכבים אחרים, הם נראים לבנים או לבנים-כחלחלים לעין האנושית, אלא אם כן הם מושפעים מהאדמה הבין-כוכבית או האטמוספרית. סיריוס, הכוכב הבהיר ביותר בשמי הלילה, ווגה, הכוכב שלפיו נמדדת בהירותם של כל הכוכבים האחרים בסולם המגניטודה הנראית, הם כוכבים מסוג A.

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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

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

Spectrum of an A-type star

Caption: 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.
Credit: IAU OAE/SDSS/Niall Deacon

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