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Lecture 18 - galaxy • Globular clusters • Planetary...

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1. William and Caroline Herschel o William Herschel - first to attempt to map our Galaxy, composer, discovered Uranus Mapping the galaxy: saw the same number of stars in every direction He saw "holes" in the galaxy, thought you were seeing further if you saw more stars However, didn't know about dust and that there could be more things hidden behind them o Caroline (his sister) - discovered comets, nebulae, not quite as impressive as William but still important, used a very advanced telescope for their time 2. The Galaxy, circa 1922 o Dutch Astronomer Jacobus Kapteyn - estimated distances by putting together parallaxes, determined that the sun is still at the center o Not much different, and he underestimated the size of the galaxy 3. Why were so many astronomers so wrong? o Galaxy is dirty o "holes" are dust, stars are born out of dust 4. RR Lyrae Variables o Fast pulsating = high luminosity o Slow pulsating = low luminosity o From luminosity you can find distance 5. Class Vote Question o Which kind of astronomical object did Shapley use to locate the center of the
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Unformatted text preview: galaxy? • Globular clusters • Planetary nebulae • Supernova remnants • Giant molecular clouds • Open clusters 6. The Infrared Galaxy Unmasked o Not available in Shapleys time o We now have them and you can see through a lot of dust o Get a much clearer picture of the galaxy o See the true shape of the galaxy, not just the nearby stars 7. The populations of the Milky Way o Can help you figure out what part of the galaxy formed first 8. How does a spiral galaxy form? o Sort these components into order beginning with the first to form, and ending with the most recent • Galactic disk • Halo • Bulge • CORRECT ORDER>>>>>>> Halo, bulge, galactic disk 9. Mapping the galaxy in the radio o Any time you have an electron in the ground state of hydrogen, (the natural state) you expect to see the "spin- flip" action o Closer to the sun- moves slower, and vice versa...
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