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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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 • Irregular • The sizes of all three types span a wide range, from • dwarf galaxies that contain 100 million (10 8 ) stars • to giant galaxies that contain 1 trillion (10 12 ) stars
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Spiral Galaxies • have a disk component spheroidal component )
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Lec25 - Pop Quiz What kind of object is located at the ?...

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