Lecture 21 - The Milky Way I

Lecture 21 - The Milky Way I - The Milky Way I ASTRONOMY 3...

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The Milky Way I ASTRONOMY 3 Lesson 21 1 The view of the northern sky (left, as one could observe it from Earth’s north pole) and of the southern sky (right, as one would see it from the south pole). The band of light and dark clouds is the Milky Way - see http://canopus.physik.uni-potsdam.de/~axm/astrophot.html
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NATURE of the Universe Review of Lesson 20 Astronomy - The Milky Way I • A neutron star is the left-over of a massive star supernova. After their formation, neutron stars are hot, rotate fast and send out energetic beams of radiation. We call these pulsars. • Special relativity postulates that the speed of light is the same everywhere in the universe, and that nothing can move any faster. • General relativity adds gravity and acceleration. It states that mass warps space-time. This causes deflection of light as it passes close-by dense mass concentrations. • Nothing getting closer than the Schwarzschild radius to a black hole can escape - not even light. Observed black hole masses range from several times to million times the mass of the Sun. 2
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NATURE of the Universe Questions from Lesson 20 Astronomy - The Milky Way I Think about (questions from Lesson 20): • How many stars are in the Milky Way? • How big is the Milky Way? 3
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• Measuring the Milky Way • Structure of the Milky Way • The formation of the Milky Way NATURE of the Universe Today’s Topics Astronomy - The Milky Way I see also Lab 7 on “Structure and Motion of Spiral Galaxies” 4
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NATURE of the Universe Measuring the Milky Way Astronomy - The Milky Way I In a dark night, one can spot not only 1,000s of star, but also a faint band of light stretching across the sky. Ancient Greeks called this band Γαλαξιας - the “Milky Way” 5 The rising Milky Way as seen from Kitt Peak (photographed by Je f Hapeman)
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NATURE of the Universe Measuring the Milky Way Astronomy - The Milky Way I The Milky Way stretches across the whole sky as depicted in this 360° view This is where we are located within the disk of the Milky Way. Sun 6
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NATURE of the Universe Measuring the Milky Way Astronomy - The Milky Way I Observations by telescopes reveal that the Milky Way band is composed of millions of stars, nebulae and dark clouds. Our largest star catalog, the Guide Star Catalog 2, used by the Hubble Space Telescope and other observatories, lists almost 1 billion stars. Extrapolation over the whole Milky Way indicates that it houses 200 billion stars . How can we find out about the size, mass and structure of the Milky Way? 7 See http://hubblesite.org/newscenter/archive/releases/star/star%20field/1999/08/ for more infos on the star field depicted above.
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NATURE of the Universe Measuring the Milky Way Astronomy - The Milky Way I Distances to the most nearby stars can be computed from the angular parallax.
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This note was uploaded on 10/13/2008 for the course ASTR 3 taught by Professor Hauser during the Spring '07 term at UCLA.

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Lecture 21 - The Milky Way I - The Milky Way I ASTRONOMY 3...

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