Editing Edwin Hubble (section)

===Universe goes beyond the Milky Way galaxy===
[[File:100inchHooker.jpg|thumb|upright=1.2|The {{convert|100|in|m|adj=on}} [[Mount Wilson Observatory#100-inch Hooker telescope|Hooker telescope]] at Mount Wilson Observatory that Hubble used to measure galaxy distances and a value for the rate of [[expansion of the universe]].]]
Edwin Hubble's arrival at Mount Wilson Observatory, California, in 1919 coincided roughly with the completion of the {{convert|100|in|m|adj=on}} [[Mount Wilson Observatory#100-inch Hooker telescope|Hooker Telescope]], then the world's largest. At that time, the prevailing view of the cosmos was that the universe consisted entirely of the [[Milky Way]] galaxy.

[[File:Hubble Tuning Fork diagram.svg|left|thumb|upright=1.5|Hubble's [[Hubble sequence|classification scheme]]]]
Using the Hooker Telescope at [[Mount Wilson Observatory|Mount Wilson]], Hubble identified [[Cepheid variable]]s, a [[Cosmic distance ladder#Standard candles|standard candle]] discovered by [[Henrietta Swan Leavitt]].<ref name="Henrietta"/> Comparing their [[Apparent magnitude|apparent luminosity]] to their intrinsic luminosity gives their distance from Earth.<ref>A Science Odyssey: People and Discoveries.</ref><ref>1929: Edwin Hubble Discovers the universe is expanding.</ref> Hubble found Cepheids in several [[Spiral galaxy#Spiral nebula|nebulae]], including the [[Andromeda Galaxy|Andromeda Nebula]] and [[Triangulum Galaxy|Triangulum Nebula]]. His observations, made in 1924, proved conclusively that these nebulae were much too distant to be part of the Milky Way and were, in fact, entire galaxies outside the Milky Way galaxy; thus, today they are no longer considered [[nebula]]e.

This was first [[Hypothesis|hypothesized]] as early as 1755 when [[Immanuel Kant]]'s ''General History of Nature and Theory of the Heavens'' appeared. Hubble's hypothesis [[Great Debate (astronomy)|was opposed]] by many in the astronomy establishment of the time, in particular by [[Harvard University]]{{En dash}}based [[Harlow Shapley#The Great Debate of 1920|Harlow Shapley]]. Despite the opposition, Hubble, then a thirty-five-year-old scientist, had his findings first published in ''[[The New York Times]]'' on {{nowrap|November 23}}, 1924,<ref name="SharovNovikov1993">{{cite book|last1=Sharov|first1=Aleksandr Sergeevich|last2=Novikov|first2=Igor Dmitrievich|title=Edwin Hubble, the discoverer of the Big Bang universe|url=https://books.google.com/books?id=ttEwkEdPc70C&pg=PA34|access-date=December 31, 2011|date=1993|publisher=Cambridge University Press|isbn=978-0-521-41617-7|page=34}}</ref> then presented them to other astronomers at the January 1, 1925, meeting of the [[American Astronomical Society]].<ref name="MB2">{{cite book |author=Bartusiak |first=Marcia |url=https://books.google.com/books?id=7XojzXh4_KEC&q=The+Day+We+Found+the+Universe |title=The Day We Found the Universe |date=2010 |publisher=Random House Digital, Inc |isbn=9780307276605 |pages=x–xi}}</ref> Hubble's results for the Andromeda galaxy were not formally published in a [[Peer review|peer-reviewed]] [[scientific journal]] until 1929.<ref>{{cite journal|first1=E. P.|last1=Hubble|author-link=Edwin Hubble|title=A spiral nebula as a stellar system, Messier 31|journal=[[The Astrophysical Journal]]|volume=69|page=103|date=1929|bibcode=1929ApJ....69..103H|doi=10.1086/143167|doi-access=free}}</ref>

Hubble's findings fundamentally changed the scientific view of the universe. Supporters state that Hubble's discovery of nebulae outside of our galaxy helped pave the way for future astronomers.<ref>{{cite news |date=2002 |title=life in the universe Astronomy Encyclopedia. Philip's. Credo Reference |location=London, England}}</ref> Although some of his more renowned colleagues simply scoffed at his results, Hubble published his findings. This published work earned him an award titled the American Association Prize and five hundred dollars from Burton E. Livingston of the Committee on Awards.<ref name="Gale E. Christianson 1996" />

Hubble also devised the most commonly used [[Galaxy morphological classification|system for classifying galaxies]], grouping them according to their appearance in photographic images. He arranged the different groups of galaxies in what became known as the Hubble sequence.<ref>{{cite book |author1=Block |first=David L. |url=https://books.google.com/books?id=HQh9hoLfoHoC&q=Hubble+sequence&pg=PA149 |title=Toward a new millennium in galaxy morphology |author2=Puerari |first2=Ivacircnio |author3=Stockton |first3=Alan |date=2000 |publisher=Springer |isbn=9780792361855 |pages=146–150}}</ref>