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Lec25 - Pop Quiz What kind of object is located at the...

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Pop Quiz What kind of object is located at the ?
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What’s at the galactic center? • S au (0.1 arcsec) = D pc *0.1= 8000 *0.1= 800 au Kepler’s 3rd law applied to orbit of object SO-2: Mass = S 3 au 3 /P 2 year = 800 3 /15 2 = 2.3 x 10 6 M sun ! => Supermassive Black Hole more than 2 million solar masses
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20. Galaxies: From Here to the Horizon Edwin Hubble (1889 – 1953) American astronomer Thus the explorations of space end on a note of uncertainty… Eventually, we reach the dim boundary – the utmost limits of our telescopes. There we measure shadows, and we search among ghostly errors of measurement for landmarks that are scarcely more substantial.
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A Universe of Galaxies In 1995, the Hubble Space Telescope observed a patch of sky in the Big Dipper for 10 days. many galaxies, each one an island of stars like our own Milky Way, were detected by counting them and correcting for the entire sky, we estimate that there are over 80 billion galaxies in the observable Universe We study the life cycles of galaxies in the same way we do stars. we piece together a life story by observing many different galaxies at various stages of their lives Studying life cycles of galaxies is more difficult than that of stars. young galaxies are only found at very great distances Movie. Click to play.
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A Universe of Galaxies Movie. Click to play.
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Classification of Galaxies Using a system invented by Edwin Hubble, astronomers classify galaxies into three major types: • Spiral • Elliptical
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