Stellar classification (Wikipedia)In astronomy, stellar classification is the classification of stars based on their spectral characteristics. Electromagnetic radiation from the star is analyzed by splitting it with a prism or diffraction grating into a spectrum exhibiting the rainbow of colors interspersed with spectral lines. Each line indicates a particular chemical element or molecule, with the line strength indicating the abundance of that element. The strengths of the different spectral lines vary mainly due to the temperature of the photosphere, although in some cases there are true abundance differences. The spectral class of a star is a short code primarily summarizing the ionization state, giving an objective measure of the photosphere’s temperature.
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Agatha Christie (Wikipedia)Dame Agatha Mary Clarissa Christie, Lady Mallowan, DBE (née Miller; 15 September 1890 – 12 January 1976) was an English writer known for her 66 detective novels and 14 short story collections, particularly those revolving around fictional detectives Hercule Poirot and Miss Marple. She also wrote the world’s longest-running play, the murder mystery The Mousetrap, which has been performed in the West End since 1952. A writer during the “Golden Age of Detective Fiction”, Christie has been called the “Queen of Crime”. She also wrote six novels under the pseudonym Mary Westmacott. In 1971, she was made a Dame (DBE) by Queen Elizabeth II for her contributions to literature. Guinness World Records lists Christie as the best-selling fiction writer of all time, her novels having sold more than two billion copies.