SPECTRAL CLASS Meaning and
Definition
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Spectral class refers to a classification system used in astronomy to categorize and classify stars based on their spectral characteristics, specifically their spectral lines and temperature. It is a way to organize and understand the diverse range of stars found in the universe by grouping them into distinct classes according to their physical properties.
The classification of stars into spectral classes is primarily based on the strength and presence of specific absorption lines in their spectra. These lines are created by elements and molecules in the star's atmosphere, and they provide valuable information about its chemical composition and temperature.
The spectral classes are denoted with a letter symbol, such as O, B, A, F, G, K, and M, with O being the hottest and most massive stars, and M being the coolest and smallest stars. Each spectral class is further subdivided into numerical values from 0 to 9, with 0 representing the hottest and 9 representing the coolest stars within each particular class. For example, the Sun is classified as a G2 star, which means it belongs to the G spectral class and is moderately hot compared to other stars within its class.
Spectral class is an essential tool for astronomers, as it helps in studying and understanding the physical properties, evolutionary stage, and lifecycle of stars. It enables the identification and classification of stars based on their temperature and chemical composition, allowing astronomers to make comparisons and draw conclusions about the behavior and nature of stars in different regions of the universe.
Etymology of SPECTRAL CLASS
The word "spectral class" is a term commonly used in astronomy to categorize stars based on their spectra, which is the distribution of electromagnetic radiation emitted by the star. The term "spectral" refers to the spectrum of light emitted by a star, and "class" refers to the categorization or classification.
The etymology of the word "spectral" can be traced back to the Latin word "spectralis", which means "of or relating to a specter or ghost". It is derived from the Latin word "spectrum", meaning "appearance" or "image", and eventually evolved to refer to the distribution of colors when light is passed through a prism.
In the field of astronomy, the classification of stars based on their spectra was first introduced by the astronomers Annie Jump Cannon and Edward C. Pickering in the late 19th and early 20th centuries.
