Menu
Home
People
Places
Arts
History
Plants & Animals
Science
Life & Culture
Technology
Reference.org
Galactocentrism
open-in-new
<h2 id="harlow-shapley-and-galactocentrism">Harlow Shapley and galactocentrism</h2> <p>Shapley had been studying the <a href="/facts/Asymmetry/U009nepR">asymmetrical</a> distribution of globular clusters, estimating the distance and location of individual objects by using <a href="/facts/Variable_stars/Ac8mp2gy">variable stars</a> as <a href="/facts/Standard_candle/Xae3hVvK">standard candles</a>. Globular clusters contain many <a href="/facts/Cepheid_variable/WQXaAFmW">cepheid variable</a> stars, whose precise relationship between luminosity and variability period was established by <a href="/facts/Henrietta_Swan_Leavitt/FI5xRzHN">Henrietta Leavitt</a> in 1908.<a class="footnote-ref" id="fnref:10" href="#fn:10"><sup>10</sup></a> Using cepheid and <a href="/facts/RR_Lyrae_variable/vjoHuKUe">RR Lyrae variables</a> to systematically chart the distribution of globular clusters, Shapley discovered that the stars in the Milky Way orbited a common center thousands of light years away from the <a href="/facts/Sun/CadPCVHh">Sun</a>.<a class="footnote-ref" id="fnref:11" href="#fn:11"><sup>11</sup></a> The <a href="/facts/Galactic_Center/TI4MwWwM">Galactic Center</a> was determined to be in the direction of the <a href="/facts/Sagittarius_(constellation)/ljtU4DQ2">Sagittarius constellation</a>, approximately 50,000 <a href="/facts/Light-year/IGc5NdQb">light-years</a> from us.<a class="footnote-ref" id="fnref:12" href="#fn:12"><sup>12</sup></a> </p> <p>In 1920 <a href="/facts/Heber_Doust_Curtis/KaGog5aI">Heber Doust Curtis</a> and Harlow Shapley participated in the <a href="/facts/Great_Debate_(astronomy)/aF4mJfJe">Great Debate</a> on the nature of nebulae and <a href="/facts/Galaxy/zCyUvEf7">galaxies</a>, and the size of the universe. Shapley believed that distant nebulae were relatively small and lay within the Milky Way Galaxy. Curtis advocated the now-accepted view that nebulae were farther away, and that other galaxies apart from the <a href="/facts/Milky_Way/ulF6lccN">Milky Way</a> therefore existed.<a class="footnote-ref" id="fnref:13" href="#fn:13"><sup>13</sup></a> By 1925, <a href="/facts/Edwin_Hubble/fpX3JlbJ">Edwin Hubble</a> had confirmed that many objects previously thought to be clouds of dust and gas and classified as "<a href="/facts/Nebulae/hG6coklY">nebulae</a>" were actually <a href="/facts/Galaxy/zCyUvEf7">galaxies</a> beyond the Milky Way.<a class="footnote-ref" id="fnref:14" href="#fn:14"><sup>14</sup></a><a class="footnote-ref" id="fnref:15" href="#fn:15"><sup>15</sup></a><a class="footnote-ref" id="fnref:16" href="#fn:16"><sup>16</sup></a> </p> <blockquote><p>"The realization, only a few decades ago, that our Galaxy is not unique and central in the universe ranks with the acceptance of the Copernican system as one of the great advances in cosmological thought." <a href="/facts/George_O._Abell/q3HwuP1G">George O. Abell</a><a class="footnote-ref" id="fnref:17" href="#fn:17"><sup>17</sup></a> </p></blockquote> <p>When astronomers realized that starlight can be absorbed by clouds of gas and dust, <a href="/facts/Infrared/44XdJNcc">infrared</a> radiation was used to penetrate the dust clouds.<a class="footnote-ref" id="fnref:18" href="#fn:18"><sup>18</sup></a> Estimates dating after 2000 locate the Solar System within the range 24–28.4 <a href="/facts/Light-year/IGc5NdQb">kilolight-years</a> (7.4–8.7 <a href="/facts/Parsec/SwSsk57J">kiloparsecs</a>) from the <a href="/facts/Galactic_Center/TI4MwWwM">Galactic Center</a> of the Milky Way galaxy.<a class="footnote-ref" id="fnref:19" href="#fn:19"><sup>19</sup></a> </p> <h2 id="shift-from-galactocentrism-to-acentrism">Shift from galactocentrism to acentrism</h2> <p>Hubble's observations of redshift in light from distant galaxies indicated that the universe was <a href="/facts/Expansion_of_the_universe/f6Uvt79B">expanding</a> and acentric.<a class="footnote-ref" id="fnref:20" href="#fn:20"><sup>20</sup></a> As a result, galactocentrism was abandoned in favor of the <a href="/facts/Big_Bang/I5T1vTnv">Big Bang</a> model of the acentric expanding universe. Further assumptions, such as the <a href="/facts/Copernican_principle/9cvC9Wc7">Copernican principle</a>, the <a href="/facts/Cosmological_principle/snaj0VNu">cosmological principle</a>, <a href="/facts/Dark_energy/6bWIYewA">dark energy</a>, and <a href="/facts/Dark_matter/y5HgX55N">dark matter</a>, eventually lead to the current model of cosmology, <a href="/facts/Lambda-CDM/DmlhJHQU">Lambda-CDM</a>. </p> <h2 id="references">References</h2> <ol> <li id="fn:1"><p>"Definition of galactocentric". Merriam-Webster Dictionary. Retrieved 6 June 2018. <a href="https://www.merriam-webster.com/dictionary/galactocentric" target="_blank">https://www.merriam-webster.com/dictionary/galactocentric</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li> <li id="fn:2"><p>"Definition of galactocentric in English". English Oxford Living Dictionaries. Retrieved 6 June 2018.[dead link] <a href="https://en.oxforddictionaries.com/definition/galactocentric" target="_blank">https://en.oxforddictionaries.com/definition/galactocentric</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li> <li id="fn:3"><p>Harrison, Edward Robert (2000), Cosmology: The Science of the Universe, Cambridge University Press, pp. 67–71, ISBN 978-0-521-66148-5 <a href="978-0-521-66148-5" target="_blank">978-0-521-66148-5</a> <a href="#fnref:3" class="footnote-back-ref">↩</a></p></li> <li id="fn:4"><p>Berendzen, Richard (1975). "Geocentric to heliocentric to galactocentric to acentric: the continuing assault to the egocentric". Vistas in Astronomy. 17 (1): 65–83. Bibcode:1975VA.....17...65B. doi:10.1016/0083-6656(75)90049-5. Retrieved 26 August 2020. <a href="https://www.sciencedirect.com/science/article/abs/pii/0083665675900495" target="_blank">https://www.sciencedirect.com/science/article/abs/pii/0083665675900495</a> <a href="#fnref:4" class="footnote-back-ref">↩</a></p></li> <li id="fn:5"><p>Bergh, Sidney van den (2011). "Hubble and Shapley—Two Early Giants of Observational Cosmology". Journal of the Royal Astronomical Society of Canada. 105 (6): 245. arXiv:1110.2445. Bibcode:2011JRASC.105..245V. <a href="/wiki/ArXiv_(identifier)" target="_blank">/wiki/ArXiv_(identifier)</a> <a href="#fnref:5" class="footnote-back-ref">↩</a></p></li> <li id="fn:6"><p>van de Kamp, Peter (October 1965), "The Galactocentric Revolution, A Reminiscent Narrative", Publications of the Astronomical Society of the Pacific, 77 (458): 324–328, Bibcode:1965PASP...77..325V, doi:10.1086/128228 <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:6" class="footnote-back-ref">↩</a></p></li> <li id="fn:7"><p>Berendzen, Richard (1975). "Geocentric to heliocentric to galactocentric to acentric: the continuing assault to the egocentric". Vistas in Astronomy. 17 (1): 65–83. Bibcode:1975VA.....17...65B. doi:10.1016/0083-6656(75)90049-5. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:7" class="footnote-back-ref">↩</a></p></li> <li id="fn:8"><p>Berendzen, Richard (1975). "Geocentric to heliocentric to galactocentric to acentric: the continuing assault to the egocentric". Vistas in Astronomy. 17 (1): 65–83. Bibcode:1975VA.....17...65B. doi:10.1016/0083-6656(75)90049-5. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:8" class="footnote-back-ref">↩</a></p></li> <li id="fn:9"><p>Berendzen, Richard (1975). "Geocentric to heliocentric to galactocentric to acentric: the continuing assault to the egocentric". Vistas in Astronomy. 17 (1): 65–83. Bibcode:1975VA.....17...65B. doi:10.1016/0083-6656(75)90049-5. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:9" class="footnote-back-ref">↩</a></p></li> <li id="fn:10"><p>van de Kamp, Peter (October 1965), "The Galactocentric Revolution, A Reminiscent Narrative", Publications of the Astronomical Society of the Pacific, 77 (458): 324–328, Bibcode:1965PASP...77..325V, doi:10.1086/128228 <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:10" class="footnote-back-ref">↩</a></p></li> <li id="fn:11"><p>Kopal, Z. (1972), "'Great Debate:' Obituary of Harlow Shapley", Nature, 240 (5381), NASA: 429–430, Bibcode:1972Natur.240..429., doi:10.1038/240429a0 <a href="https://antwrp.gsfc.nasa.gov/htmltest/gifcity/shapley_obit.html" target="_blank">https://antwrp.gsfc.nasa.gov/htmltest/gifcity/shapley_obit.html</a> <a href="#fnref:11" class="footnote-back-ref">↩</a></p></li> <li id="fn:12"><p>Kopal, Z. (1972), "'Great Debate:' Obituary of Harlow Shapley", Nature, 240 (5381), NASA: 429–430, Bibcode:1972Natur.240..429., doi:10.1038/240429a0 <a href="https://antwrp.gsfc.nasa.gov/htmltest/gifcity/shapley_obit.html" target="_blank">https://antwrp.gsfc.nasa.gov/htmltest/gifcity/shapley_obit.html</a> <a href="#fnref:12" class="footnote-back-ref">↩</a></p></li> <li id="fn:13"><p>Berendzen, Richard (1975). "Geocentric to heliocentric to galactocentric to acentric: the continuing assault to the egocentric". Vistas in Astronomy. 17 (1): 65–83. Bibcode:1975VA.....17...65B. doi:10.1016/0083-6656(75)90049-5. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:13" class="footnote-back-ref">↩</a></p></li> <li id="fn:14"><p>Roberts, Jacob (2017). "A Giant of Astronomy". Distillations. 3 (3): 6–11. Retrieved May 16, 2018. <a href="https://www.sciencehistory.org/distillations/magazine/a-giant-of-astronomy" target="_blank">https://www.sciencehistory.org/distillations/magazine/a-giant-of-astronomy</a> <a href="#fnref:14" class="footnote-back-ref">↩</a></p></li> <li id="fn:15"><p>Hubble, Edwin (December 1926). "Extragalactic nebulae". Astrophysical Journal. 64 (64): 321–369. Bibcode:1926ApJ....64..321H. doi:10.1086/143018. <a href="https://doi.org/10.1086%2F143018" target="_blank">https://doi.org/10.1086%2F143018</a> <a href="#fnref:15" class="footnote-back-ref">↩</a></p></li> <li id="fn:16"><p>Hetherington, Edith W.; Hetherington, Norriss S. (2009). Astronomy and culture. Santa Barbara, Calif.: Greenwood Press/ABC-CLIO. p. 174. ISBN 978-0313345364. <a href="978-0313345364" target="_blank">978-0313345364</a> <a href="#fnref:16" class="footnote-back-ref">↩</a></p></li> <li id="fn:17"><p>Berendzen, Richard (1975). "Geocentric to heliocentric to galactocentric to acentric: the continuing assault to the egocentric". Vistas in Astronomy. 17 (1): 65–83. Bibcode:1975VA.....17...65B. doi:10.1016/0083-6656(75)90049-5. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:17" class="footnote-back-ref">↩</a></p></li> <li id="fn:18"><p>"Meet the Stargazers". WHYY. Retrieved 6 June 2018. <a href="https://www.pbs.org/seeinginthedark/meet-the-stargazers/in-history.html" target="_blank">https://www.pbs.org/seeinginthedark/meet-the-stargazers/in-history.html</a> <a href="#fnref:18" class="footnote-back-ref">↩</a></p></li> <li id="fn:19"><p>Francis, Charles; Anderson, Erik (June 2014). "Two estimates of the distance to the Galactic Centre". Monthly Notices of the Royal Astronomical Society. 441 (2): 1105–1114. arXiv:1309.2629. Bibcode:2014MNRAS.441.1105F. doi:10.1093/mnras/stu631. S2CID 119235554. <a href="https://doi.org/10.1093%2Fmnras%2Fstu631" target="_blank">https://doi.org/10.1093%2Fmnras%2Fstu631</a> <a href="#fnref:19" class="footnote-back-ref">↩</a></p></li> <li id="fn:20"><p>Berendzen, Richard (1975). "Geocentric to heliocentric to galactocentric to acentric: the continuing assault to the egocentric". Vistas in Astronomy. 17 (1): 65–83. Bibcode:1975VA.....17...65B. doi:10.1016/0083-6656(75)90049-5. <a href="/wiki/Bibcode_(identifier)" target="_blank">/wiki/Bibcode_(identifier)</a> <a href="#fnref:20" class="footnote-back-ref">↩</a></p></li> </ol>