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Download Linking Asteroids and Meteorites through Reflectance Spectroscopy
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Survey of the Universe Tom Burbine [email protected] Quiz #4 • • • • Next Wednesday Covers up to today Cumulative You can bring in one 8 ½ by 11 inch piece of paper with anything written on it Cecilia Payne-Gaposchkin (1900-1979) • Payne argued that the great variation in stellar absorption lines was due to differing amounts of ionization (due to differing temperatures), not different abundances of elements Cecilia Payne-Gaposchkin (1900-1979) • She proposed that most stars were made up of Hydrogen and Helium • Her 1925 PhD Harvard thesis on these topics was voted best Astronomy thesis of the 20th century Hertzsprung-Russell Diagram • Ejnar Hertzsprung and Henry Norris Russell independently discovered this diagram’s usefulness • Both plotted spectral type (temperature) versus stellar luminosity • Saw trends in the plots • Did not plot randomly http://www.youtube.com/watch?v=01 U7ZUKVW8o Remember • Temperature on x-axis (vertical) does from higher to lower temperature • O – hottest • M - coldest Hertzsprung-Russell Diagram • Most stars fall along the main sequence • Stars at the top above the main sequence are called Supergiants • Stars between the Supergiants and main sequence are called Giants • Stars below the Main Sequence are called White Dwarfs wd white dwarfs • giant – a star with a radius between 10 and 100 times that of the Sun • dwarf – any star with a radius comparable to, or smaller than, that of the Sun Classifications • Sun is a G2 V • Betelgeuse is a M2 I Radius • Smallest stars on the main sequence fall on the bottom right • Largest stars on main sequence fall on the top left • At the same size, hotter stars are more luminous than cooler ones • At the same temperature, larger stars are more luminous than smaller ones Main Sequence Stars • Fuse Hydrogen into Helium for energy • On main sequence, mass tends to decrease with decreasing temperature What does this tell us • The star’s mass is directionally proportional to how luminous it is • L = M3.5 • More massive, the star must have a higher nuclear burning rate to maintain gravitational equilibrium • So more energy is produced Things to remember • 90% of classified stars are on main sequence • Main sequence stars are “young” stars • If a star is leaving the main sequence, it is at the end of its lifespan of burning hydrogen into helium Remember • Largest stars on main sequence are O stars • Largest stars that can exist are supergiants Classifications • • • • • Sun is a G2 V Betelgeuse is a M2 I Vega is a A0 V Sirius is a A1 V Arcturus is a K3 III Stellar Evolution • Changes that occur while stars age • The mass of a star is the main factor deciding its fate because mass determines the gravitational force and the amount of fuel Any Questions?