To determine the spectral class of a star, you typically need the following pieces of spectrum data:
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Absorption Lines: The presence and strength of absorption lines in the star's spectrum is crucial. Different elements and molecules absorb light at specific wavelengths, and the pattern of these lines can indicate the star's composition, temperature, and pressure.
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Temperature: The effective temperature of the star can be derived from the spectral data by analyzing the distribution of the emitted radiation, often using Wien's Law or by fitting the spectrum to theoretical models.
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Spectral Features: Specific features such as hydrogen lines (e.g., Balmer series), helium lines, and metal lines (like those of calcium, iron, and magnesium) are key indicators for classifying the star. The strength and width of these lines also provide information about the star's physical properties.
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Continuum Radiation: The general shape of the continuum radiation (the background light spectrum) can also provide context for temperature and classifying luminosity.
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Luminosity Class: Additional information, such as the luminosity of the star (which may require distance measurements), helps distinguish between different luminosity classes (e.g., dwarf, giant) within the same spectral class.
By combining all these aspects, astronomers can classify a star into one of the spectral classes (O, B, A, F, G, K, M), which is based primarily on temperature, spectral characteristics, and a range of properties associated with each class.
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