Discoveries 1917 100” Hooker Telescope on Mt

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Discoveries 1917 100” Hooker telescope on Mt. Wilson 1920 “Debate on the Scale of the Universe” Interpretaon of the “Spiral Nebulae” Harlow Shapley “only gas clouds” within a single galacc Universe Sun far from the center Heber CurGs Sun at the center of our relavely small galaxy all the spiral nebulae are other galaxies Measure the size – HOW?? Fall 2018 1 Yardstck 1.Brightness (magnitude) 2.Parallax 3.Cepheid Variables November 23, 1924 Edwin Hubble, 35, published in the New York Times his discovery that there were many galaxies further away from the Milky Way. Fall 2018 2 MMilkyilky Way 1838 Discovery of stellar parallax 1838 Discovery of stellar parallax (F.Bessel) ) 1 1 1 Parsec = Parsec = = = 3.263.26 ly P (arcsec) (arcsec) 1 1 Mpc = 10= 106 parsecs = 3.26 million lightyears parsecs = 3.26 million lightyears Fall 2018 Fall 2018 213 Cepheid Variables At Harvard (Society For the Collegiate InstrucGon of Women) Oberlin and Radcliff Colleges she was capGvated by Astronomy. Variable stars vary periodically in brightness HenrieUa LeaviU HenrieUa found ~50) Cepheid variables Fall 2018 4 Edwin Hubble ! Confirmed the extra galacGc nature of nebulae using Cepheid variable yardsGck ! Observed that every galaxy appears to be moving away from every other one Farthest ones moving faster Fall 2018 5 Velocit measurement Doppler Effect Aer Einstein Fall 2018 6 Speed vs. Distance Fall 2018 7 Hubble Constant Not constant! Fall 2018 8 What is going on? Q1 Moving away? – the track back and find where they started Finally Copernicus is verified – we are not at the center of the Solar system – we are not at the center of the Galaxy – we are not at the center of the Universe Q2 Where are they going? For a Gme it was thought that Gravity would pull it all together Fall 2018 9 Technical Advances 200 in Hale telescope Hubble Space Telescope Palomar Observatory Fall 2018 10 Cosmological Principle ! Space is homogenous ! Space is isotropic Looks the same from any posi5on Fall 2018 11 Deep Field No stars in our galaxy Deep field (north) Deep field (south) Homogeneity is observed on scales large compared to distances between galaxies Fall 2018 12 Geomety -1 0 1 2 3 4 Distance between them (equal spacing) Elas5c string Distance depends on 5me Fall 2018 13 Geomety-2 expansion Fall 2018 14 .

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Chapter I Review Papers Harlow Shapley
Chapter I Review Papers Harlow Shapley Downloaded from https://www.cambridge.org/core. IP address: 170.106.40.40, on 25 Sep 2021 at 08:30:59, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0074180900042340 Helen Sawyer Hogg and Willis Shapley remembering Willis Shapley fielding questions on his father Downloaded from https://www.cambridge.org/core. IP address: 170.106.40.40, on 25 Sep 2021 at 08:30:59, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S0074180900042340 SHAPLEY'S DEBATE Michael Hoskin Cambridge University The attempt to make three-dimensional sense of the Milky Way goes back to a most unlikely origin: the English antiquary of the early eighteenth century, William Stukeley, remembered today for associating the Druids with Stonehenge. Stukeley came from Lincolnshire and so was a fellow-countryman of Isaac Newton, and as a result he was privileged to talk with the great man from time to time. In his Memoirs of Newton Stukeley records one conversation they had in about 1720, in which Stukeley proposed that the Sun and the brightest stars of the night sky make up what we today would term a globular cluster, and this cluster is surrounded by a gap, outside of which lie the small stars of the Milky Way in the form of a flattened ring. Stukeley's remarkable suggestion was recorded only in his manuscript memoirs, and had no effect on the subsequent history of astronomy.
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Our Milky Way.Key
Our Milky Way Learning Objectives ! What is the Milky Way? The Herschels thought we were at the center of our Galaxy...why were they wrong? ! How did Shapley prove we aren’t at the center? What are globular clusters? Cepheid Variable stars? ! How do we use Cepheid Variables to measure distance? ! What are the components of our Galaxy? What color are old stars? Young stars? Does our Galaxy get older or younger as you move out (i.e. from the disk to the halo)? ! How do we know our Galaxy is a spiral galaxy? ! Do stars in our Galaxy’s disk orbit as Kepler’s Laws would predict? What is a rotation curve? Why does our Galaxy’s rotation curve suggest dark matter exists? The Milky Way ! Our Galaxy is a collection of stars, nebulae, molecular clouds, and stellar remnants ! All bound together by gravity ! Connected by the stellar evolution cycle Determining the Shape of our Galaxy ! The number of 6400 ly stars were counted in all directions from 1300 ly the Sun by Sun Caroline Herschel and her brother William ! They assumed that all stars have the same brightness and that space contains no dust – these are incorrect assumptions ! They thus concluded that the Sun is at the center of the Universe - which is not true The Importance of Dust ! Dust dims and reddens starlight ! There is more dust toward the center of the Galaxy ! Consequence: We underestimate the number of stars in one direction ! We appear to be near the center, but we’re not Us Star Sun Can’t see stars here (if we’re looking for blue light from them) How Do We Find the Galactic Center?
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At the Harvard Observatory
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- How Telescopes Changed our Understanding of our Universe - Suggested Script PRESENTATION NOTE: This presentation can take 45 minutes to an hour. To shorten it, you may want to allow your audience to vote on the three or four questions they would like discussed. See Slide 3 for the questions covered in this presentation. 1. 400 years ago, before telescopes, our understanding of the universe was very different. This is what was believed: We live on a spherical ball orbited by the rest of a finite, spherical universe. Earth does not move. It is the center of the universe. Our Sun orbits the Earth, as do all the other planets and the Moon. The stars are distant objects, always perfect and unchanging. How did telescopes & associated technologies unlock the secrets of the universe and help us toward the understanding we have today where Earth is no longer at the center of the universe? Instead, we know that ours is a small planet orbiting a star in the suburbs of a large galaxy filled with billions of other stars and planets, surrounded by billions of other galaxies becoming increasingly ever distant from each other by the expansion of space. This is the story of how telescopes continuously changed our understanding of the universe and our place in it - transforming our view of our universe. And we still have much more to discover! 2. Before telescopes, we could only use our eyes and a variety of measuring instruments to plot the positions and movements of objects in the sky to create a limited understanding of our universe.
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1929NL Homeed.Pdf
National Aeronautics and Space Administration Home Edition Age of the Universe: Cosmic Times Size of the Universe: 2 Billion Years 1929 280 Million Light Years Andromeda Nebula lies outside the Milky Way Galaxy Spiral Nebulae are indeed “Island Universes” stronomer Edwin Hubble, inch reflector partially resolved a of the Mount Wilson few of the nearest, neighboring AObservatory at Pasadena, [spiral] nebulae into swarms of California, has solved the mystery stars.” One of the nearby nebulae of the spiral nebulae. The spiral Dr. Hubble photographed was the nebulae look like hazy pin-wheels Andromeda Nebula. He estimates in the sky. He has determined it is as large as the Milky Way that these objects are much more and holds as much matter. It may distant than previously thought. contain some three to four billion Therefore, they are distant galaxies stars that produce one-billion times and not part of our own Milky Way the light of the Sun. galaxy. In the process, Dr. Hubble was also able to determine the These photographs showed there distance to the spiral Andromeda were individual stars in the nebula. Nebula. They also showed some of the stars changed in brightness over Dr. Hubble’s observations support time. Known as Cepheid variable Image credit: Hale Observatories, courtesy AIP Emilio Segre Visual Archives the views Dr. Heber Curtis stars, these stars were the key Edwin Hubble at Mount Wilson Obser- expressed in a debate with Dr. to determining distances to the vatory Harlow Shapley in 1920. Curtis nebulae. The true brightness of stated that bright diffuse nebulae the Cepheids in the nebulae Swan Leavitt of the Harvard College are fairly close to Earth and are Hubble studied was known from Observatory and by Dr.
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The Cosmic Web: Mysterious Architecture
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Henry Norris Russell
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Connecting the Scientific and Socialist Virtues of Anton Pannekoek
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Early Edition
National Aeronautics and Space Administration Early Edition Age of the Universe: Cosmic Times Size of the Universe: Infinite 1919 300,000 Light Years Sun’s Gravity Bends Starlight— Einstein’s Theory Triumphs ir Joseph Thompson said, Sir Joseph made this announce stein said that the change in the “One of the greatest...of ment at a meeting of both the light’s position could be measured Sachievements in the history Royal Society and the Royal As by taking photographs of the star of human thought” was a new pre tronomical Society in London on when its light is passing close to diction Dr. Albert Einstein made. November 6, 1919. A large num the Sun, then photographed again This prediction was proven true ber of astronomers and physicists later in the year when the distant during the total eclipse of the Sun were at the meeting. Everyone star’s light is not passing close on May 29, 1919. His prediction was very excited, and they all to the Sun. These photographs was that light bends around large, agreed that observations made must be taken very carefully and massive objects like the Sun. during the eclipse proved Dr. Ein very precisely. However, what makes the predic stein’s prediction to be correct. Dr. tion different from other predic Albert Einstein is a Professor of Dr. Einstein’s General Theory of tions is that Einstein said the light Physics at the University of Ber Relativity explains that “gravity” bends around objects twice as lin and also the Director of Kaiser and “inertia” are the same.
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