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TEMPERATURE

TEMPERATURE. A star’s color depends on its surface temperature. How hot is Vega?. l max at 4600 Å. So, Wien’s law tells us. BB spectrum. Vega is 500 K hotter than the Sun. l ( Å ). SPECTRUM. Never Say Never.

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TEMPERATURE

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  1. TEMPERATURE

  2. A star’s color depends on its surface temperature

  3. How hot is Vega? lmaxat 4600 Å So, Wien’s law tells us BB spectrum Vega is 500 K hotter than the Sun l (Å)

  4. SPECTRUM

  5. Never Say Never “there is no conceivable means by which we shall one day determine the chemical composition of the stars” • Auguste Comte (1798 - 1857) • French Philosopher (bad prophet) • Founder of the Social Sciences • Espoused the philosophy of positivism – as seen on the Brazilian flag – “Love as a principle and order as the basis; progress as the goal.”

  6. Blackbody spectrum Continuous spectrum l l

  7. Classify Stars into groups based on Spectral Data

  8. The Spectral Sequence • In 1890, Edward Pickering and his assistant at Harvard classified thousands of stellar spectra at Harvard. • Named them ‘A’ through ‘Q’ • A. Cannon ‘improved’ the scheme and ordered it by temperature: O,B,A,F,G,K,M • Subdivided each into 0 through 9 (AO: hot – A9:cooler) E. Pickering and his housekeeper W. Fleming A. J. Cannon classifying one of 200,000 spectra by eye for 25¢ an hour ($6 today)

  9. Annie Jump Cannon (1863 - 1941) studied over 250,000 spectra as part of the Harvard Observatory program to classify stars

  10. Spectral Type Classification System O BAFGKM Oh Be A Fine Girl/Guy, Kiss Me (Long Time)! Only Brilliant Astronomers Find Glorious Knowledge Manning Large Telescopes Only Boring Astronomers Find Gratification Knowing Mnemonics Like That… 50,000 K 1,000 K Temperature

  11. MAGNITUDE

  12. Flowchart of Key Stellar Parameters

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