Extragalactic Astronomy: From Pioneers to Big Science
Date Issued
2016
Author(s)
•
D'ONOFRIO, MAURO
•
•
Lattis, James M.
•
Haynes, Martha P.
•
Giovanelli, Riccardo
•
Karachentseva, Valentina
•
Longair, Malcolm S.
•
Lindblad, Per-Olof
•
•
de Carvalho, Reinaldo Ramos
•
Kaifu, Norio
•
Bland-Hawthorn, Jonathan
•
Djorgovski, Stanislav George
•
Bianchi, Luciana
•
Calzetti, Daniela
•
Fabbiano, Giuseppina
•
Combes, Françoise
•
Chiosi, Cesare
•
Sulentic, Jack W.
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 [116]. 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. [116]), but they only sketched its shape in a notebook. They also
wrote that “the nebulæ are resolved [into stars] without exception” [116]. 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 [255] 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 [34] 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.
Coverage
From the Realm of the Nebulae to Populations of Galaxies
Volume
435
Start page
1
Ads BibCode
2016ASSL..435....1R
Rights
restricted
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