A remarkable sammelband containing 17 separately-paginated offprints from the Astrophysical Journal, of which 15 are by Hubble, documenting his discoveries on the size, structure, and properties of the universe in the period 1925-43.

N.p. N.p, 1925-1943.

A remarkable and comprehensive collection of offprints, including 15 by Hubble (1889-1953) and two by his assistant Milton Humason (1891-1972), tracing the evolving understanding of galaxies in the period 1925-43. The present volume contains all but two of the papers published in this period singled out for detailed discussion in the National Academy of Sciences’ biographical memoir of Hubble.Edwin Hubble, by his inspired use of the largest telescope of his time, the 100-inch reflector of the Mount Wilson Observatory, revolutionized our knowledge of the size, structure, and properties of the universe” (Mayall, p. 175). “Edwin Hubble’s cosmological researches established the existence of other galaxies and an expanding universe. Instruments, observations and theories available to Hubble were accessible to others as well, but it was Hubble who forged a brilliant synthesis, which he then demonstrated in persuasive fashion … Hubble’s cosmology [is] one of the great accomplishments of the human intellect” (Hetherington). The collection notably includes (Nos. 1 to 4 in the list of contents below) the papers in which Hubble settled the ‘Great Debate’ as to whether ‘nebulae’ were objects within the Milky Way, as advocated by Harlow Shapley, or ‘island universes’ similar to but outside it, the view championed by Heber Curtis. In No. 1, Hubble wrote that NGC 6822 was “the first object definitely assigned to a region outside the galactic system.” “In 1929 Hubble published his epochal paper on M31, the great Andromeda Nebula. Based on 350 photographic plates taken at Mount Wilson, his study provided evidence that M31 is a giant stellar system like the Milky Way Galaxy” (Britannica). These observations “ultimately established that our universe was a thousand trillion times larger than previously believed, filled with myriad galaxies like our own. This discovery dramatically reshaped how humans understood their place in the cosmos” (Bartusiak). Other papers (Nos. 6, 7, 13) provide observational evidence in support of Hubble’s epochal discovery in 1929 of the ‘expanding universe’ – that galaxies recede from us with a velocity proportional to their distance (that paper is not present here – it was not published in the Astrophysical Journal), while Nos. 12 & 16 discuss the implications of Hubble’s observations for deciding among the competing models of the expanding universe. “In addition to his renowned study of the red-shifts of nebulae, Hubble undertook a detailed and comprehensive study of the nebulae as individuals, and he set up in 1926 a classification system generally used as the standard to the present time [No. 3]. A revision of this system based on manuscript notes left by Hubble has recently been included by Allan Sandage in his discussion of the magnificent collection of photographs reproduced in The Hubble Atlas of Galaxies (Carnegie Institution of Washington, Publication No. 618, 1961)” (Mayall, p. 187). ‘The distribution of extra-galactic nebulae’ (No. 10), the longest scientific paper of Hubble’s career, he reported his conclusions from the observation of 80,000 extragalactic nebulae. “With the aid of charts and graphs, the author, who was still referring to his work as ‘reconnaissance,’ declared his hypothesis confirmed … On the broadest scale available to humankind, the universe is indeed homogeneous” (Christianson, p. 236). None of the offprints offered here are listed on ABPC/RBH.

Provenance: William A. Baum (1924-2012), American astronomer (signature on front free endpaper, a few marginal pencil annotations in text). “Baum returned to Caltech after the war and obtained his PhD in physics in 1950. He was offered a position at Mt. Wilson and Palomar Observatories, where he developed instrumentation capable of counting individual photoelectrons during long exposures with the Hale 200-inch telescope at Palomar. He worked with astronomers such as Edwin Hubble, Walter Baade, Allan Sandage and Halton Arp” (http://www.azarchivesonline.org/xtf/view?docId=ead/lowell/WA_Baum.xml).

“Centuries of speculation about the possible existence of island universes similar to our galaxy were coming to a head early in the twentieth century, with attention focusing on spiral nebulae. In favour of the view that the spiral nebulae were external galaxies was their resemblance to the hypothetical spiral structure of the Milky Way. Also, V. M. Slipher’s discovery at the Lowell Observatory beginning in 1912 that spiral nebulae have extraordinarily high radial velocities (velocity components in the line of sight) gave new life to the theory that these objects were distant stellar systems, although the subsequent discovery of a few stars in our galaxy that also have high radial velocities somewhat weakened the argument.

“Opposing an extragalactic nature was the absence of observable spiral nebulae in lower galactic latitudes, which seemed to link the spirals physically to our stellar system, although the observed distribution could also be attributed to a hypothetical encircling opaque material. Observations of bright novae in spiral nebulae also argued for short distances to the spirals, until much fainter novae not in conflict with the island universe theory were detected beginning in 1917. The most compelling argument against regarding the spiral nebulae as external galaxies was Adriaan van Maanen’s claimed measurement at the Mount Wilson Observatory of internal motions in the spiral nebula M101, the import of which was explained forcibly by Harlow Shapley. If spiral nebulae were extragalactic systems comparable in size to our own galaxy (estimates of whose size Shapley had recently increased significantly) and were rotating with a period of 85,000 years (as reported by van Maanen), the outer edges of the nebulae would be traveling faster than the speed of light. Hubble had no conclusive evidence in 1917 regarding the nature of spiral nebulae, though he thought that ‘the Great spirals with their enormous radial velocities and insensible proper motions apparently lie outside our system’.

“Following service in World War I, Hubble went to the Mount Wilson Observatory. There photographic plates taken with a new 100-inch telescope revealed the presence of variable stars in the irregular nebula NGC 6822 and in several spiral nebulae. Cepheid variable stars would be the key to measuring distances and settling the debate over whether the nebulae were outside our galaxy. While determining the periods of variable stars in the Small Megallanic Cloud, Henrietta Leavitt of Harvard had found it ‘worthy of notice that … the brighter variables have the longer periods.’ Since stars in this distant nebulae were all at approximately the same distance from the earth, there existed a common scale that could be used to convert the measured apparent magnitudes, a function of intrinsic brightness and distance, into absolute magnitude. The period-luminosity relation was soon calibrated, primarily by Shapley on a few nearby Cepheids in our own galaxy whose distances were determined trigonometrically, in a calculation as brilliant as it was bold. Shapley used the new and still unproven relation to measure distances to globular clusters of stars and outline the frame of our galaxy.

“Writing to Shapley in 1923, Hubble informed him that he had found variable stars in NGC 6822 and intended to hunt for more and investigate their periods and light curves. Shapley wrote back, ‘What a powerful instrument the 100-inch is in bringing out those desperately faint nebulae.’ But Hubble’s success had not followed automatically from access to the 100-inch telescope. Shapley, who had moved from Mount Wilson to the Harvard Observatory in 1921, might have extended his own work to spiral nebulae … It was Hubble, inspired by the island universe theory, who presciently focused his attention on a consequential problem, searching for variable stars in spiral nebulae, finding them, and using them to advance our understanding of the universe.

“Employing the period-luminosity relation for Cepheid variable starts to calculate the absolute magnitude from the observed period and then comparing this estimated intrinsic magnitude to the observed magnitude diminished due to the distance of the nebula, Hubble derived distances placing spiral nebulae far beyond the boundary of our galaxy. Early in 1924 he wrote to Shapley, ‘You will be interested to hear that I have found a Cepheid variable in the Andromeda nebula (M31)’ … And in 1923, before examining M31, Hubble had already found in NGC 6822 indications of Cepheids, to be fully established as such after more observations in 1924 [No. 1].

“When Hubble’s letter arrived, Shapley remarked, ‘Here is the letter that has destroyed my universe’ … In August 1924 Hubble had more variables and was beginning to theorize about the significance of his data … Hubble’s discovery of Cepheids in spiral nebulae and the distance determination confirming that spiral nebulae are independent galaxies was announced on 1 January 1925 at an Astronomical Society meeting. This preliminary paper was followed by further work presented in convincingly voluminous and thorough detail over the next four years [Nos. 1, 2, 4]. Hubble strengthened his case with evidence from novae, from the observed colors of the brightest stars, and from star counts, leaving van Maanen’s claimed rotations as the only shadow on an otherwise consistent picture of spiral nebulae as island universes …

“For a decade Hubble largely ignored the discrepancy … In the early 1930s, though, following a tentative revival of interest in van Maanen’s results, Hubble took up the problem again. An astronomer’s plates were considered private property, and Hubble would have to take new photographs to check van Maanen’s measurements … He invited to participate in the new measurements Seth Nicholson, whose earlier measures van Maanen had claimed as corroboration. Nicholson did not explicitly recant his earlier testimony, but observers could easily have formed that impression. Hubble published a brief note pointing to van Maanen’s results as the outstanding discrepancy in the conception of nebulae as extragalactic systems and presenting a table of his own remeasures of four spiral nebula, results establishing the existence of systematic errors in van Maanen’s rotations [No. 11]” (Hetherington).

Hubble’s most famous discovery is that of the expanding universe, reported in the Proceedings of the National Academy of Sciences in 1929, ‘A Relation between Distance and Radial Velocity among Extra-Galactic Nebulae.’ “By 1929 Hubble had obtained distances for eighteen isolated galaxies and for four members of the Virgo cluster. In that year he used this somewhat restricted body of data to make the most remarkable of all his discoveries and the one that made his name famous far beyond the ranks of professional astronomers. This was what is now known as Hubble’s law of proportionality of distance and radial velocity of galaxies” (DSB).

Much of the work in determining radial velocities of nebulae was carried out by Milton Humason, who had started work as a janitor at Mount Wilson in 1917, but became a staff member in 1919 and worked closely with Hubble for many years. “To establish his now-famous relation between radial velocity and distance, Hubble needed data for many more extragalactic nebulae. In 1929, from two spectrograms of 33- and 45-hour exposures, Humason obtained a radial velocity for the galaxy NGC 7619 of +3,779 km/sec, over twice as great as the highest previously known velocity. Within less than a year, Humason again doubled the highest radial velocity known … In 1930, soon after this work, Humason put into operation a specially designed spectrograph more than twice as fast as his former instruments … By the next year, Humason could report radial velocities of 46 galaxies … Hubble and Humason used these velocities in their 1931 paper [No. 7] on the velocity-distance relation. With the much larger body of data now available, they confirmed the linear velocity-distance relation first documented by Hubble in 1929” (Encyclopedia of Cosmology). “By 1935, [Hubble] and Humason had velocities for 100 additional nebulae at distances as much as 30 to 40 times further than the Virgo cluster [No. 13]. The scientific case was unimpeachable” (Hetherington, p. 147).

Various models of the expanding universe had been proposed, notably by the Belgian astronomer Georges Lemaître, by E. A. Milne at Oxford, and by Fritz Zwicky, a physicist at the California Institute of Technology. “Hubble ostensibly took up the problem of discriminating on the basis of observations among Lemaître’s, Milne’s and Zwicky’s models of the universe. He was joined by Richard Tolman (1881-1948), a theoretical physicist at the California Institute of Technology who had developed the mathematical foundations of relativistic cosmology …

“Hubble and Tolman [No. 12] began with the observed fact of red shifts in the light from distant nebulae, which they were inclined to interpret as Doppler shifts due to recessional motions. Not wanting to neglect prematurely the possibility of other causes, however, they continued to use the phrase ‘apparent velocity of recession’ and discussed methods of distinguishing between recessional motion and some other cause of the red shifts. Before the link between theory and observation could be forged, various complicating factors in the treatment of the data also had to be dealt with. Theoretical relations were calculated in each case for real and apparent velocities of recession. Hubble and Tolman formulated methods for interpreting the nature of the red shifts, but in their published paper they did not report a definite conclusion. Given the many observational problems any conclusion could be only tentative” (Hetherington, pp. 148-9).

In ‘Effects of red shifts on the distribution of nebulae’ (No. 16), “Hubble added two additional groups of nebular counts to the three groups already discussed in his 1935 paper with Tolman. After a detailed analysis of the observational data, and a comparison with the theoretical models computed with Tolman, Hubble found that ‘the observations may be fitted into either of two quite different types of universes. If the red-shifts are velocity shifts, the model is closed, small and dense. It is rapidly expanding, but over a long period the rate of expansion has been steadily diminishing … On the other hand, if red-shifts are not primarily due to velocity shifts, … the velocity-distance relation is linear; the distribution of nebulae is uniform; there is no evidence of expansion, no trace of curvature, no restriction to the time scale. The sample, it seems, is too small to indicate the particular type of universe we inhabit’” (Mayall, pp. 202-3).

The first systematic classification of nebulae was attempted by William Herschel in his paper titled ‘Catalogue of One Thousand New Nebulae and Clusters of Stars’ (1786). Later Lord Rosse (1850) gave the term ‘spiral’ to some of Herschel’s nebulae by using his new 1.8m telescope, the ‘Leviathan of Parsonstown’. The classification scheme of Herschel was considered unwieldy and complicated, but was probably the only one referred to consistently until the early twentieth century. Today Hubble, in his ‘Extra-galactic nebulae’ [No. 3], is credited with the first usable classification scheme of galaxies.

In Part I of this paper, Hubble set forth his classification of nebulae, with detailed discussion of his classification of extragalactic nebulae. He emphasized that ‘the basis of the classification is descriptive and entirely independent of any theory.’ The photographs of typical elliptical, irregular, normal, and barred spirals appearing in this paper are perhaps the most familiar set of photographs in present-day astronomy books …

“Part II of this paper contains a statistical study of some 400 extragalactic nebulae …

Finally, using what observational evidence was available, he determined the mean density of nebulae in space, and applied this result in the theory of general relativity to get the radius of curvature of the finite universe – ‘600 times the distance at which normal nebulae can be detected with the 100-inch reflector.’ This calculation represented the boldest probe of the universe yet made, and it greatly stimulated theoretical work in cosmology” (Mayall, pp. 192-3).

“Hubble’s seminal paper, simply called ‘Extra-galactic nebulae’” (Christianson, p. 176), was intended by Hubble as a confirmation of the theory of galaxy evolution put forward by the English astronomer James Jeans in 1919. “The passing years would cast doubt on the premise of nebular evolution outlined by Hubble. Jeans, whose champion Hubble had become, was eventually forced to admit that all attempts to explain dynamically the origin and development of the spiral arms were failures – and remain so to this day. Conversely, Hubble’s somewhat modified classification scheme has weathered the test of time and continues to serve as the accepted standard for the vast majority of galaxies. The great astronomer Walter Baade, Hubble’s colleague at Mount Wilson for more than two decades, spoke eloquently of the genius of its formulator during a lecture given at Harvard in 1958:

‘I have used [the classification scheme] for thirty years, and, although I have searched obstinately for systems that do not fit it, the number of such systems that I finally found – systems that really present difficulties to Hubble’s classification – is so small that I can count it on the fingers of my hand’” (Christianson, p. 177).

In the introduction to ‘The distribution of extra-galactic nebulae’ (No. 10), “containing an immense amount of new material, Hubble referred to his work on distance estimates of the nebulae as giving a ‘hasty sketch of some of the general features of the Observable Region as a unit. The next step,’ he said, ‘was to follow the reconnaissance with a survey – to repeat carefully the explorations with an eye to accuracy and completeness’ … This paper, 69 pages in length, incorporates counts of about 80,000 nebulae identified on photographs taken with the Mount Wilson 60- and 100-inch reflectors. In this work, generally recognized as a classic, Hubble obtained on a firm quantitative basis, for the first time, information on the large-scale occurrence of obscuring matter along the plane of the galaxy, on the numbers of the nebulae to successively fainter magnitude limits, on the tendency of nebulae to cluster, and on the average density of matter in extragalactic space. The impact of these new data on cosmology and galactic structure investigations can hardly be overestimated. There are innumerable references to this work in many subsequent papers by theorists and observers” (Mayall, pp. 200-201).

Distribution of luminosity in elliptical nebulae’ (No. 5) is an initial attempt to understand the internal structure of galaxies by examining the variation of their brightness from the centre to the outer edges. Hubble concluded this paper by noting that ‘The nuclei of the nebulae appear to be relatively more concentrated, and in the outer regions the luminosity falls off faster than the density, as would be expected in the case of finite rotating bodies such as the nebulae.’ At the time, no elliptical nebula had been resolved into stars, and this result was available for consideration by rival theories of ellipticals as gaseous or stellar systems” (Mayall, p. 196). Nos. 15 &16 also study the brightness of nebulae, but this time comparing it for all the nebulae in a given volume of space. “Hubble wrote in The Realm of the Nebulae (p. 59), ‘The relative numbers of giants and dwarfs and normal objects – more precisely, the frequency-distribution of absolute magnitudes among these nebulae – form the ‘luminosity-function.’ It was assumed that the luminosity-function remains constant throughout the regions covered by the surveys – that the function is independent of distance or direction – that the giants do not tend to congregate in one region and the dwarfs in another region. The assumption has not been fully established by direct observations, but it seems reasonable and it is consistent with all information available at the present time’” (Mayall, p. 203).

In the last paper in this collection, ‘The direction of rotation in spiral nebulae’ (No. 17), Hubble returned to his old interest in the formation of spiral nebulae. “He was particularly hopeful of determining the direction of nebular rotation, which had also preoccupied such prominent astronomers as Vesto Slipher and Bertil Lindblad. There were only three possible answers to the question: the arms may be trailing behind the central regions in all spirals, as Slipher believed; the arms may be leading the rotation, as Lindblad postulated; or the direction of rotation may vary from nebula to nebula … The breakthrough had come during a run in early February 1941 … he had enjoyed three nights of excellent seeing, enabling him to obtain the spectrum of a critical test nebula, the only one among a thousand such objects whose visual orientation was almost perfect. It was as he had always thought: the spiral arms trail behind the more rapidly rotating nucleus. In the months ahead he succeeded in establishing the same rotational pattern in three more spirals, and by inference added another eleven to the fold … Perhaps in time this discovery would shed light on the evolution of the universe, as Hubble had hoped to do when he first developed his classification scheme for the nebulae” (Christianson, p. 290).


  1. HUBBLE, Edwin. N.G.C. 6822, a remote stellar system. Separately-paginated offprint from Astrophysical Journal 62 (1925) (journal pagination 409-433). Contributions from the Mount Wilson Observatory No. 304. Pp. [1], 2-25, with two full-page photographic plates.
  2. HUBBLE, Edwin. A spiral nebula as a stellar system. Messier 33. Separately-paginated offprint from Astrophysical Journal 63 (1926) (journal pagination 236-274). Contributions from the Mount Wilson Observatory No. 310. Pp. [1], 2-39, with four full-page photographic plates.
  3. HUBBLE, Edwin. Extra-galactic nebulae. Separately-paginated offprint from Astrophysical Journal 64 (1926) (journal pagination 321-369). Contributions from the Mount Wilson Observatory No. 314. Pp. [1], 2-49, with three full-page photographic plates. (8/83)
  4. HUBBLE, Edwin. A spiral nebula as a stellar system. Messier 31. Separately-paginated offprint from Astrophysical Journal 69 (1929) (journal pagination 103-158). Contributions from the Mount Wilson Observatory No. 376. Pp. [1], 2-55, [1], with six full-page photographic plates.
  5. HUBBLE, Edwin. Distribution of luminosity in elliptical nebulae. Separately-paginated offprint from Astrophysical Journal 71 (1930) (journal pagination 231-276). Contributions from the Mount Wilson Observatory No. 398. Pp. [1], 2-46, [2, blank], with one full-page photographic plate.
  6. HUMASON, Milton. Apparent velocity shifts in the spectra of faint nebulae. Separately-paginated offprint from Astrophysical Journal 74 (1931) (journal pagination 35-42). Contributions from the Mount Wilson Observatory No. 426. Pp. [1], 2-8, with two full-page photographic plates.
  7. HUBBLE, Edwin & HUMASON, Milton. The velocity-distance relation among extra-galactic nebulae. Separately-paginated offprint from Astrophysical Journal 74 (1931) (journal pagination 43-80). Contributions from the Mount Wilson Observatory No. 427. Pp. [1], 2-38, [2, blank].
  8. HUBBLE, Edwin. Nebulous objects in Messier 31 provisionally identified as globular clusters. Separately-paginated offprint from Astrophysical Journal 76 (1932) (journal pagination 44-69). Contributions from the Mount Wilson Observatory No. 452. Pp. [1], 2-26, with four full-page photographic plates.
  9. HUBBLE, Edwin. The surface brightness of threshold images. Separately-paginated offprint from Astrophysical Journal 76 (1932) (journal pagination 106-116). Contributions from the Mount Wilson Observatory No. 453. Pp. [1], 2-11, [1, blank].
  10. HUBBLE, Edwin. The distribution of extra-galactic nebulae. Separately-paginated offprint from Astrophysical Journal 79 (1934) (journal pagination 8-76). Contributions from the Mount Wilson Observatory No. 485. Pp. [1], 2-69, [3, blank]. (11/33)
  11. HUBBLE, Edwin. Angular rotations of spiral nebulae. Separately-paginated offprint from Astrophysical Journal 81 (1935) (journal pagination 334-335). Contributions from the Mount Wilson Observatory No. 514. Pp. [1], 2, [2, blank]. (11/20)
  12. HUBBLE, Edwin & TOLMAN, Richard. Two methods of investigating the nature of the nebular red-shift. Separately-paginated offprint from Astrophysical Journal 82 (1935) (journal pagination 302-337). Contributions from the Mount Wilson Observatory No. 527. Pp. [1], 2-36.
  13. HUMASON, Milton. The apparent radial velocities of 10 extra-galactic nebulae. Separately-paginated offprint from Astrophysical Journal 83 (1936) (journal pagination 10-22). Contributions from the Mount Wilson Observatory No. 531. Pp. [1], 2-13, [2, blank], with one full-page photographic plates.
  14. HUBBLE, Edwin. The luminosity function of nebulae. I. The luminosity function of resolved nebulae as indicated by their brightest stars. Separately-paginated offprint from Astrophysical Journal 84 (1936) (journal pagination 158-179). Contributions from the Mount Wilson Observatory No. 548. Pp. [1], 2-22.
  15. HUBBLE, Edwin. The luminosity function of nebulae. II. The luminosity function as indicated by residuals in velocity-magnitude relations. Separately-paginated offprint from Astrophysical Journal 84 (1936) (journal pagination 270-295). Contributions from the Mount Wilson Observatory No. 549. Pp. [1], 2-26.
  16. HUBBLE, Edwin. Effects of red shifts on the distribution of nebulae. Separately-paginated offprint from Astrophysical Journal 84 (1936) (journal pagination 517-554). Contributions from the Mount Wilson Observatory No. 557. Pp. [1], 2-38, [2, blank].
  17. HUBBLE, Edwin. The direction of rotation in spiral nebulae. Separately-paginated offprint from Astrophysical Journal 97 (1943) (journal pagination 112-118). Contributions from the Mount Wilson Observatory No. 674. Pp. [1], 2-7, [1, blank], with four full-page photographic plates. (13/44)

Bartusiak, The day we found the universe, 2009. Christianson, Edwin Hubble, 1995. Hetherington, ‘Hubble’s cosmology,’ American Scientist 78 (1990), pp. 142-151. Mayall, ‘Edwin Powell Hubble 1889-1953,’ Biographical Memoirs, National Academy of Sciences, 1970.

Seventeen offprints bound in one volume, large 8vo (249 x 164mm), numerous diagrams and tables in text. Mid-twentieth-century cloth, spine gilt lettered (‘Galaxies / Hubble / and / Humason’), typescript table of contents at front. Fine.

Item #5430

Price: $12,500.00

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