The Role of Images in Astronomical Discovery Read online

  introduced diagrams, which are rough copies of those drawn at the telescope. They have

  been executed by the pantagraph process employed by the Patent Type Founding Company

  for reproducing the weather charts for the daily newspapers.”49

  Following Messier 51, many other spirals were identified and sketched. The search for

  spirality superseded the drive for resolvability into stars. Drawing gained favor as the indis-

  pensable tool of recording and spirality was soon found in several other “nebulae.” “Internal

  to the Rosse project there began a concerted effort to ‘resolve’ the nebulae not so much into

  stars but into a ‘few normal forms,’ the most powerful being, of course, the spiral.”50 The

  observers sometimes went overboard in seeing spirality where there was none, e.g. object

  h 311 (NGC 1514) turned out to be a planetary nebula, hence the comment of Wilhelm

  49 Fourth Earl of Rosse, Observations of Nebulae and Clusters of Stars Made with the Six-Foot and the Three-Foot Reflectors at Birr Castle from the Year 1848 up to the Year 1878, Scientific Transactions of the Royal Dublin Society, 1878, Vol. II, p. 4.

  50 O. W. Nasim, Observing by Hand: Sketching the Nebulae in the Nineteenth Century, Chicago: University of Chicago Press, 2013, p. 54.

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  2. Portraying Cosmic Whirlpools

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  Tempel about “spiral addiction” at Birr Castle. Nevertheless, the majority of objects identi-

  fied as spirals were confirmed as such by later observations, including well known galaxies

  such as Messier 99 in Coma Berenices, Messier 101 in Ursa Major and Messier 33 in Trian-

  gulum. “An interesting question: how many objects are actually spiral galaxies? A modern

  analysis yields a number of sixty-five (out of 71) – an astonishingly large fraction and a

  fine proof of the quality of the Birr Castle observations.”51 Some of the non-spiral objects

  were galaxies of other morphological types.

  The Rosse project cast its net broadly.52 The Birr Castle program surveyed the whole sky

  for more nebulae and star clusters. The program added thousands of objects to those already

  identified and catalogued. Missing objects were searched and classified, if needed, as spu-

  rious observations or objects mistaken for their incorrect positions on the sky. Parsons’

  son Lawrence, the Fourth Earl of Rosse, prepared a comprehensive article of the decades

  of work. It was published in The Scientific Transactions of the Royal Dublin Society.53

  Reading the paper and the observer’s notes, one comes across several mentions of spiral-

  ity. Moreover, from the many drawings and notes, it is clear that the Birr Castle observers

  also identified several other fundamental features of galaxy morphology, such as spheroids,

  ellipticals, edge-on orientations or spindle shapes, barred structures, etc. The Leviathan

  observers also discovered multiple groupings and clusters of “nebulae.”

  Meticulous and reliable observations of “nebulae,” many rendered in sketches and por-

  traits, were the first aim of Parsons’ empiricist enterprise. Textual notes added details on

  “resolvability,” characteristic features, etc. Parsons’ team continued to call them “nebulae,”

  cautious not to be carried away by the ongoing dispute about the nature of these mysterious

  objects. It is remarkable that, even through furious ongoing debates, the “Telescope Earl”

  remained neutral and objective, always keeping a cautious stand on the nature of “nebulae.”

  He never jumped on the Nebular Hypothesis bandwagon. Perhaps it was because he consid-

  ered himself first and foremost an engineer, with all his efforts directed to produce the most

  powerful machine ever to observe the sky. He was happy to leave the detailed analysis and

  interpretation to others whose minds and temperaments were more at ease with speculative

  work. Having built the very last of the great reflectors with metal mirrors, Parsons left a

  stunning legacy.

  A Prudent Pioneer Opening a New Era

  The technological achievements of Birr Castle, with the recordings and publications, were

  momentous in the history of astronomy. The telescopes, the model of their operation and

  management, the assiduity and rigor of the observing programs and the competence of the

  51 W. Steinicke, Birr Castle Observations of Non-Stellar Objects and the Development of Nebular Theories, in William Parsons, 3rd Earl of Rosse: Astronomy and the Castle in Nineteenth-Century Ireland, C. Mollan (editor), Manchester: Manchester University Press, 2016, pp. 250–252.

  52 See O. W. Nassim, Observing by Hand: Sketching the Nebulae in the Nineteenth Century, Chicago: University of Chicago Press, 2013, Chapters 1 and 2.

  53 Fourth Earl of Rosse, Observations of Nebulae and Clusters of Stars Made with the Six-Foot and the Three-Foot Reflectors at Birr Castle from the Year 1848 up to the Year 1878, Scientific Transactions of the Royal Dublin Society, 1878, Vol. II.

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  Part I – Images and the Cosmos

  Fig. 2.10 Transformational Image: The Spirality of Messier 51 (a) Messier 51 sketched. Por-

  trait of the spiral galaxy (left panel) by Leviathan observers. This is a negative representation,

  brighter regions shown darker. From 4th Earl of Rosse (1878), Scientific Transactions of the Royal

  Dublin Society. Courtesy of The George Peabody Library, The Sheridan Libraries, Johns Hopkins

  University.

  observers were key components for the success of the new observatory. These key elements

  carefully put together under William Parsons’ leadership prepared the way for the great

  reflectors of the twentieth century (Chapter 3). Although he was not always successful,

  he continuously had innovation on his mind. Parsons (with the probable assistance of the

  Countess) attempted to photograph the Moon using the 3-ft telescope. We know that he

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  2. Portraying Cosmic Whirlpools

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  Fig. 2.10 (b) Messier 51 photographed (right panel) with the Hubble Space Telescope. This is a neg-

  ative black-and-white reproduction, again with bright regions showing dark. Credit: NASA, ESA.

  Courtesy of Zoltan Levay (STScI).

  consulted the British photographic pioneer Henry Fox Talbot (1800–1877), but that effort

  failed. The early photographic material was just of too low a sensitivity, and the 3-ft mount

  lacked the tracking advantage of the equatorial mount.54 Parsons even tried to install a

  spectroscope on the 6-ft telescope. In all these efforts, the Rosse team brought observational

  54 William’s son, Lawrence the 4th Earl, later transformed the original 3-ft reflector with its Herschelian mounting into a refurbished 36-inch telescope with equatorial mounting and a water-powered drive.

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  Part I – Images and the Cosmos

  astronomy to another level of scientific rigour and technical know-how. “We may remark

  that the establishment at Birr Castle had in miniature many of the features of the modern

  observatory: a large telescope financed by a wealthy benefactor, a permanent skilled

  maintenance staff in optical and mechanical workshops, a small core of staff astronomers,

  and even an occasional ‘guest astronomer’ program with accommodation available in the

  Castle.”55


  Parsons and his team of observers were undeniable precursors: they opened a new astro-

  nomical field, research on galaxies. “The discoveries of spiral galaxies at Birr Castle, the

  excellent visual renditions made with the 72-inch Leviathan, and the main publications from

  this work in the Philosophical Transactions of the Royal Dublin Society for 1844, 1850,

  and 1861 reveal details of galaxy morphology that are beyond amazing: spiral arms, bars,

  rings, knots, nuclei, etc. The final summary of these observations in the Scientific Transac-

  tions of the Royal Dublin Society for 1879–1880 is in a way the first galaxy morphological

  atlas, even if galaxies are mixed with other ‘nebulae’.”56

  Unfortunately, neither Parsons nor his expert collaborators had any clue of the true nature

  of the “nebulae.” Fully aware of this, Parsons wrote: “I think we have no fair ground even

  for plausible conjecture; and as observations have accumulated, the subject has become,

  to my mind at least, more mysterious and more inapproachable.”57 It goes without saying

  that Parsons was right in his prudence at not letting the prejudiced mind see structure that

  did not exist and he warned his observing team to be most skeptical and restrained. Never-

  theless, observers had managed to put together the portraits of the main nebular silhouettes

  (Fig. 2.11).

  Notwithstanding major observational advances backed by superb images, a lot of skepti-

  cism remained with regard to the new images. Could spirality be an illusion from scattered

  light or an artefact of the instrument, for example circular patterns imprinted on the primary

  mirror during grinding and polishing? Further technical advances were needed to provide

  the answer. Better telescopes, not necessarily larger than the Leviathan, were a critical step.

  Throughout the later part of the nineteenth century, major improvements were made to

  reflecting and refracting telescopes, providing aficionados of “nebulae” with more optical

  power. John Herschel graciously recognized the men behind this progress and the significant

  technical improvements, as he wrote in 1864: “Thanks to the exertion of Lord Rosse, Mr.

  Lassell, Messrs. Nasmyth and de la Rue in England, and Messrs. Steinheil, Foucault and

  Porro in Germany and France, as regards reflecting telescopes, and to those of Fraunhofer,

  Meez, Cauchoix, Clarke, Cook, Secretan, Ross, and Dallmeyer as regards refractors.”58

  Great advances were made. Innovations included glass mirrors instead of metallic ones,

  optical coatings for better and durable reflection, sturdy mounting systems for accurate

  55 D. W. Dewhirst and M. Hoskin, The Rosse Spirals, Journal for the History of Astronomy, 1991, Vol. XXII, pp. 257–266.

  56 Ronald Buta, e-mail exchange with the author, 2012.

  57 C. Parsons (editor), The Scientific Papers of William Parsons, Third Earl of Rosse 1800–1867, Cambridge: Cambridge University Press, 2011.

  58 J. Herschel, General Catalogue of Nebulae and Clusters of Stars, Philosophical Transactions of the Royal Society of London, 1864, vol. 154, pp. 1–137.

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  2. Portraying Cosmic Whirlpools

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  Fig. 2.11 Sketches of several nebulae. Messier 51 (no. 6) and Messier 99 (no. 5) by William Par-

  sons and Messier 31 or Andromeda Galaxy, (no. 14) by George P. Bond are easily recognized. From

  Alexander (1852), On the Origin of the Forms and the Present Condition of Some of the Clusters of

  Stars, and Several of the Nebulae. Courtesy of John G. Wolbach Library, Harvard College Observa-

  tory, 2016.

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  Part I – Images and the Cosmos

  pointing of the telescope, and more precise clockwork for better tracking of celestial objects

  as the celestial sphere rotated. A new generation of telescopes and systematic observing

  approaches led to a re-organized exploration of the world of “nebulae.” All was falling into

  place for the entry of astrophotography, as photographic techniques made giant leaps in

  sensitivity and ease of use.

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  3

  From Celestial Snapshots to Photographing

  the Realm of Galaxies

  I wish to mention (i) That photography has now shown itself to be capable

  of giving us pictures of nebulae that are superior to those made by eye and

  hand. (ii) That anything that can be seen by the eye with a telescope of

  a certain size can be photographed, and, further than this, stars that are

  too faint to be seen in this telescope can yet be photographed by it with

  sufficient exposure.

  Andrew Ainslie Common 1

  A comparison of the best drawings and photographs of nebulae reveals

  at once the existence of considerable discrepancies between the forms

  depicted by methods so widely different. The actual nebulae, as pho-

  tographed, have almost no resemblances to the figures.

  James Keeler 2

  This series of telescopes, by revealing to all men, graphically, by means

  of exquisite photographs, a Universe of which the Earth, the Sun and the

  Milky Way are but an infinitesimal part, will bring to the world a greater

  Renaissance, a better Reformation, a broader science, a more inspiring

  education, a nobler civilization.

  George Ritchey 3

  How Daguerreotype and Photography Made Astrophotography

  Astronomy was one among many scientific disciplines that greatly benefited from the intro-

  duction of photography. In enabling true-to-nature representation, with the resulting “objec-

  tivity shock,” photography brought about a fundamental transformation. In several ways, it

  meant a revolutionary change in the recording of scientific objects and phenomena.

  1 A. A. Common, Telescopes for Astronomical Photography, Nature, 1884, Vol. 31, pp. 38–40.

  2 J. Keeler, Note on a Case of Differences between Drawings and Photographs of Nebulae, Publications of the Astronomical Society of the Pacific, 1895, Vol. 7, pp. 279–282.

  3 G. Ritchey, The Modern Reflecting Telescope and the New Astronomical Photography, Transactions of the Optical Society, 1928, Vol. 29, p. 197.

  59

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  Part I – Images and the Cosmos

  The Ideal Splash and the Distractions

  In order to illustrate this change, Lorraine Daston and Peter Galison most appropriately

  introduced the concept of “discovery shock.”4 To help us grasp the early impact of pho-

  tography, these authors described the momentous experiences of British physicist Arthur

  Mason Worthington (1852–1916). Starting in 1875, Worthington studied the physics of

  splashes or the behavior of splashing liquid drops, their dynamics and the evolution of their

  structure, using millisecond light flashes. From the latent images left on his retina for around

  10 milliseconds, Worthington depicted and drew the sequence of the evolving stages of the

  shape of splashing liquid drops. The sequences Worthington drew were of symmetrical and

  regularly shaped ribs, arms, bubbles and spouts; these certainly were pleasing to the eye.

  Worthington carefully produced many representative drawings that he published in profes-

  sional journals over several years.<
br />
  In 1894, Worthington managed to photograph the process. To his astonishment, the beau-

  tiful symmetry he thought he had faithfully captured was gone, shattered, as if it were a

  chimera. Instead, the photographs revealed greater irregularities than the majority of his

  drawings suggested. “Plunged into doubt, Worthington asked how it could have been that,

  for so many years, he had been depicting nothing but idealized mirages, however beauti-

  fully symmetrical.”5 Almost desperate, Worthington wrote “I have to confess that in looking

  over my original drawings I find records of many irregular and unsymmetrical figures, yet

  in compiling the history it has been inevitable that these should be rejected, if only because

  identical irregularities never recur. Thus the mind of the observer is filled with an ideal

  splash – an Auto-Splash – whose perfection may never be actually realized.”6

  A – P H OT O G R A P H I N G “ N E B U L A E , ” P I O N E E R I N G

  C E L E S T I A L P H OT O G R A P H Y

  Spiral Skeptics

  The development of scientific illustrations and the use of drawings had provided scientists

  from the seventeenth to the nineteenth century with an efficient way to ensure a greater

  degree of objectivity in describing geological landscapes, clouds, animals, plants, fossils

  and “nebulae.” By the middle of the nineteenth century, the tradition was solidly in place.

  But images of faint astronomical objects were flimsy. How real were the objects and features

  described and drawn by the observers using the Leviathan, even if it was the most power-

  ful telescope in operation? Were the drawings just fanciful reconstructions of the mind

  by imaginative observers? It was not an uncommon worry, especially as several observers

  of “nebulae” got carried away by curvilinear shapes they believed to have seen or cap-

  tured. With enthusiastic bias, some started seeing spirality where there was none, as in the

  well-observed Orion Nebula or Crab Nebula in the constellation of Taurus. Even the cau-

  tious George Bond stated from his observations that the Orion Nebula “may, in fact, be

  4 L. Daston and P. Galison, Objectivity, New York: Zone Books, 2007.

  5 L. Daston and P. Galison, Objectivity, New York: Zone Books, 2007, p. 13.

  6 A. Worthington, The Splash of a Drop. London: Society for Promoting Christian Knowledge, 1895, p. 74.