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|Title:||Extragalactic Astronomy: From Pioneers to Big Science||Authors:||RAMPAZZO, Roberto
Lattis, James M.
Haynes, Martha P.
Longair, Malcolm S.
de Carvalho, Reinaldo Ramos
Djorgovski, Stanislav George
Sulentic, Jack W.
|Issue Date:||2016||Volume:||From the Realm of the Nebulae to Populations of Galaxies||Series:||ASTROPHYSICS AND SPACE SCIENCE LIBRARY||Number:||435||First Page:||1||Abstract:||At the beginning of the XIX century one of the scientific issues driving the research of astronomers, like the Herschels, was to test if all the nebulæ can be resolved into stars. This research continued uninterruptedly for many years surveying the nebulæ in the Charles Messier’s “Catalogue des n´ebuleuse et des amas d’´etoiles” published in 1780 and triggered the building of the cosmological telescopes of the time, among which the famous Leviathan of Parsonstown, a reflector with a mirror of 72 inch diameter (1,82m) at Birr Castle in Ireland . William Parsons, the Third Earl of Rosse, and other astronomers, such as Thomas Romney Robinson, re-observed with the Leviathan a large fraction of nebulæ already inspected byWilliam Herschel. They revealed the spiral structure of the Whirlpool nebula M51 for the first time in 1845 , (see e.g. ), but they only sketched its shape in a notebook. They also wrote that “the nebulæ are resolved [into stars] without exception” . However, the co-existence of stars and nebulosity was annotated by John Herschel describing the Magellanic Clouds in “Outlines of Astronomy”, published in 1849. The stellar nature of nebulæ remained therefore unsolved. The first photographic experiments started with Louis Daguerre in 1824, but only in 1839 Franc¸ois Arag`o presented this technique at the Acad´emie des Sciences in Paris. In 1900 photographic cameras were already in use in the astronomical context and photographs by James E. Keeler at the Lick Observatory showed that thousands of nebulæ have a spiral structure similar to M51. The first descriptive classification of nebulæ was devised by Max Wolf in 1908  while the spectra of spiral nebulæ started to be obtained in around 1913 by Vesto Slipher, who obtained the first measure of redshift. Photography began to dissect the structure of spiral nebulæ and Heber Curtis  in 1918 showed that “a band of absorbing or occulting matter is crossing some spiral nebulæ”. At the beginning of the 1920s times were mature enough to tackle the fundamental question about their nature: are these nebulæ part of the Galaxy or are separated Island Universes? This non-trivial question was the core of the Great Debate that took place in 1920 at the Smithsonian Institute in Washington D.C.. The first Chapter of this book briefly outline the history of astronomy of these years, introducing the work of the pioneers of extragalactic astronomy in the United States and in Europe (Section 1.2). Their different opinions about the nature of spiral nebulæ and about the impact of interstellar absorption are reviewed. This historical introduction brings us to the threshold of the Second World War (WWII). The war represented a watershed for the growth of extragalactic astronomy in several countries, whose effects are still present today. For a significant part of the XXth century astronomers didn’t know the scientific results of many colleagues affiliated to different institutes, because the world, and Europe in particular, was divided into blocks. For many years Journals publishing extra-galactic papers and even Catalogs were not easily accessible in many countries. Many authors used only their mother language, complicating the diffusion of scientific results. Only recently, the policy of using English as the standard language for science communication and that of giving free access to scientific papers, has been widely encouraged by Journals. Section 1.3 reports the interviews to several astronomers, active in many areas of the world, about the most important developments of extragalactic research after WWII. Astronomy is a science that has seen in these years a true revolution. Several international institutions were founded together with consortia leading to the accomplishment of ground based and space telescopes equipped with sophisticated instrumentations. In parallel, big international research teams started to work on well defined projects. Astronomers entered in the so-called Big Science era. Today they are no more alone at their telescopes working hard in the long cold winter nights, they are members of large teams and work on digital data that are stored in their computers. Quite often the youngest astronomers have never experienced a whole night at the telescope! Section 1.4 sketches the evolution of detectors and instruments. Their development at the focal planes of ground based telescopes and on board of space facilities determined an increase of spatial and spectral resolution, the widening of the electro-magnetic coverage from gamma-ray to radio, and the possibility of mapping the distant Universe providing the galaxy properties and distribution, and characterizing the different environments. Section 1.5 deals with the jump to atmospheric free observations provided by space facilities. The growth of space missions provided the first panchromatic view of galaxies. Our interviews sketch the most relevant space missions in the ultraviolet, infrared and X-ray wavelength intervals together with their main achievements. The explosion of computing power as well as the introduction of the World- Wide-Web network revolutionized our way of working and, as a consequence, also the extragalactic research field. The studies of galaxy evolution through computer simulations bore as soon as computers appeared. Semi-analytical and purely numerical approaches replaced the analytical ones. The interviews in Section 1.6 describe such a passage that has largely affected the present and future possibilities of understanding galaxies.||URI:||http://hdl.handle.net/20.500.12386/26593||URL:||https://link.springer.com/chapter/10.1007%2F978-3-319-31006-0_1||ISBN:||978-3-319-31004-6||DOI:||10.1007/978-3-319-31006-0_1||Bibcode ADS:||2016ASSL..435....1R||Fulltext:||reserved|
|Appears in Collections:||2.01 Capitoli o saggi in libro|
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