What are the criteria used in spectral classification of stars?
Spectral classification of stars is primarily based on their temperature, which is determined by analyzing their spectra, specifically the absorption lines. Stars are categorized into types O, B, A, F, G, K, and M, arranged from hottest to coolest. Each type is further subdivided into numerical subcategories (e.g., A0 to A9). Other criteria include luminosity and the presence of certain spectral lines.
What are the different spectral classes and what do they signify about the stars?
Spectral classes are designated as O, B, A, F, G, K, and M, indicating a star's temperature and color. O-type stars are the hottest and bluest, while M-type stars are the coolest and reddest. These classes also provide information about a star's chemical composition and intrinsic luminosity.
How does spectral classification help in understanding the lifecycle of a star?
Spectral classification helps in understanding the lifecycle of a star by categorizing stars based on their spectral characteristics, primarily temperature and intrinsic brightness, which are indicative of a star’s current stage in its life cycle, from formation to main sequence, and eventual decline as a giant or supergiant and then a remnant.
How was the spectral classification system developed and who were the key contributors?
The spectral classification system was developed by astronomers Henry Draper, Annie Jump Cannon, and Edward C. Pickering in the early 20th century. Draper initiated the cataloging of stellar spectra, while Cannon refined the classification into the Harvard system, classifying stars by temperature. Edward C. Pickering supported and directed the work at the Harvard College Observatory.
How does spectral classification influence our understanding of stellar temperatures and compositions?
Spectral classification categorizes stars based on their spectra, affecting our understanding of their temperatures and compositions. It helps determine a star's temperature by identifying specific absorption lines, indicating the presence of particular elements. This allows astronomers to infer chemical composition and evolutionary status, enhancing models of stellar life cycles.