Saturday, March 13, 2010


Posted by Darin Hayton on 03/13 at 10:30 PM

The latest in my Pluto project posts. This post, on the anniversary of the announcement of the discovery of a trans-Neptunian object, looks as some of those earliest announcements to see how they portrayed the discovery and who got credit for making it.

On 13 March 1930 Vesto Slipher, the director of the Lowell Observatory, announced to the world that the Lowell Observatory had found a trans-Neptunian object. The timing of the announcement was no accident: by reporting the discovery on the 149th anniversary of William Herschel’s discovery of Uranus and on Percival Lowell’s 75th birthday, the Lowell Observatory was attempting to rehabilitate Percival Lowell’s standing in the astronomical community by validating his mathematical work and by appropriating the anniversary of the first planetary discovery.

The Lowell Observatory Circular announcing the discovery of a trans-Neptunian body (13 March 1930)

Slipher’s goal to validate Lowell’s theoretical work is clear from the first sentence: “The finding of this object was a direct result of the search program set going in 1905 by Dr. Lowell in connection with his theoretical work on the dynamical evidence of a planet beyond Neptune.” Lowell’s reputation had suffered after his rather grandiose claims about life on Mars.1 The discovery of this trans-Neptunian body confirmed Lowell’s status as a proper astronomer and helped make up for his wild speculations about canals on Mars and the race of Martians suffering some horrible, planet-wide drought. Slipher’s announcement continued to praise the Lowell family, in this case Percival’s brother Lawrence, the president of Harvard University: “The earlier searching work, laborious and uncertain because of the less efficient instrumental means, could be resumed much more effectively early last year with the very efficient new Lawrence Lowell telescope specially designed for this particular problem.”

Only after giving pride of place to Percival and Lawrence did Slipher mention, in passing, Clyde Tombaugh: “Some weeks ago, on plates he made with this instrument [the Lawrence Lowell telescope], Mr. C. W. Tombaugh, assistant on the staff, using the Blink Comparator, found a very exceptional object, which since has been studied carefully.” Beyond this single mention, Tombaugh is not mentioned again in the circular. Slipher goes on to point out that “Astronomer Lampland” and “Astronomer E. C. Slipher” have photographed the object and observed it visually with the observatory’s large refractor. Moreover, the “new object was first recorded on the search plates of January 21 (1930), 23rd, adn 29th, and since February 19 it has been followed closely.” Lampland apparently did much of the work confirming that the object “conforms closely to the expected behavior of a Trans-Neptunian body, at about Lowell’s predicted distance.” Slipher concludes that “its position and distance appear to fit only those of an ojbect beyond Neptune, and one apparently fulfilling Lowell’s theoretical findings.” Clyde Tombaugh’s role in discovering this object was, apparently, of little significance.

Tombaugh’s marginal status in the initial announcement cannot be explained away by the circular’s brevity. Ten days later Slipher and Tombaugh wrote a short article for Science News-Letter describing for yet a broader audience the discovery of this trans-Neptunian planet. Once agin, this article is a paean to Percival Lowell:

Twenty-five years ago, Dr. Percival Lowell, director and founder of the Observatory at Flagstaff, Ariz., began a mathematical investigation for a planet beyond Neptune, based upon certain unaccounted for motions of the planet Uranus. The problem of locating such a body in the heavens was a very difficult one, and involved an enormous amount of intricate computations. In 1914 he announced in an extensive memoir as a result of his mathematical work, the position of the predicted body.
The search of the sky directed by Dr. Lowell’s theoretical investigation was begun by photography in 1905 and has been continued with interruptions to the present time. Use has been made of the best available instruments covering that band around the sky in which the planets travel. Early in 1929 the new Lawrence Lowell telescope, a special instrument for the research, was put in operation.2

Clearly Lowell deserves all the credit for both the intellectual work and the effort to start and direct the search for this planet. Even 15 years after his death Lowell was still directing the search. Tombaugh, by contrast, is given credit only for having “found an object on his plates with this telescope.” This image of Tombaugh as merely carrying out Lowell’s project is reinforced in Tombaugh’s own portion of the article: “In searching for the new planet I was carrying out a systematically arranged program and was fortunate in being assigned to this work with the splendid new Lowell photographic telescope.” Tombaugh admitted that although he had found the object on the photographic plates, he was “not a mathematician, and so the work on the planet is being carried on largely by the senior members of the observatory staff.”3 Even Tombaugh himself, at least initially, saw little agency in his own actions and assumed that he deserved little credit for having discovered this object.

Slipher and Tombaugh’s article in Science News-Letter announcing the discovery of the trans-Neptunian planet (Source: Science News-Letter (22 March 1930), 179)

The effort to celebrate Lowell’s extended beyond the staff at his eponymous observatory. A second article in the same issue of Science News-Letter, this one written by Harlow Shapely at Harvard and Frank Schlesinger at Yale, was even more insistent on Lowell’s credit and Tombaugh’s invisibility.

If this planet was found near the place predicted by the late Percival Lowell the discovery constitutes a great triumph for him and also for the present staff of the Lowell Observatory. To find so faint an object is an extremely difficult task and reflect great credit on Dr. Lampland and Dr. Slipher. … To Professor Percival Lowell, born in Boston on March 13, 1855, belongs the credit, though he died on November 12, 1916 and now rests in a stone mausoleum at the observatory he founded, close to the dome of the great telescope with which he did his work.4

Schlesinger continues, minimizing the efforts needed to discover Uranus—“Great as was Herschel’s discovery, Uranus was literally waiting to be picked up by some keen eye.”— and Neptune—“his [Lowell’s] was a task far more difficult than that of Leverrier or Adams.” Lowell’s task was doubly difficult for the calculations were more complicated than those needed to predict Neptune and the observations were more onerous than those needed to see Uranus. Clearly Percival Lowell’s hard work and brilliance deserve most of the credit for finding this new planet. If there is additional credit to be distributed, it should go to the Lowell Observatory astronomers:

C. W. Tombaugh was the astronomer who first actually observed it, but to the entire Lowell Observatory staff, including its director, Dr. V. M. Slipher, his brother E. C. Slipher, Dr. C. O. Lampland, K. P. Williams, T. B. Gill, G. H. Edwards, and J. C. Duncan belongs the credit for the third planetary discovery.5

The early reports of the discovery of that trans-Neptunian object we call Pluto expended considerable effort to celebrate Percival Lowell’s agency while, at the same time, effaced Clyde Tombaugh’s. By the 1970s, this relationship had inverted: Tombaugh is the hero of the story while Lowell is the eccentric aristocrat who provided the funds for the project. Like the announcement of Pluto’s discovery, that change was not accidental. Subsequent posts here will offer some explanations for how and why that shift occurred.

1See “Lowell’s Canals on Mars” for a brief account of his efforts to find life on Mars.
2V. M. Slipher, “The Sun’s New Trans-Neptunian Planet,” Science News-Letter (22 March 1930), 179.
2Clyde W. Tombaugh, “The Sun’s New Trans-Neptunian Planet,” Science News-Letter (22 March 1930), 179.
4Harlow Shapley and Frank Schlesinger, “Astronomers Acclaim New Planet,” Science News-Letter (22 March 1930), 180.
5Ibid., 186.

Tags: clyde tombaugh, percival lowell, pluto, uranus, v.m. slipher, william herschel