The term "calcium triplet" typically refers to a specific feature observed in the spectrum of stars, particularly in the ultraviolet and visible light ranges. This feature consists of three closely spaced absorption lines associated with ionized calcium (Ca II). The calcium triplet lines are prominent in the spectra of late-type stars, especially red giants, and are most commonly observed in the following wavelengths: 1. **H and K lines** (3968 Å and 3934 Å) 2.
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