The Glass Universe

by Dava Sobel

Henry Norris Russell followed some of Hertzsprung’s same ideas to similar conclusions about size, brightness, and distance. Based on his own calculations, Russell posited that Miss Leavitt’s variables and their yellow counterparts in the Milky Way were all giants.

  Miss Leavitt herself did not pursue these lines of research. She advanced the hunt for new variables in her third of the sky and went on fine-tuning the magnitudes of the North Polar Sequence, allowing others to build on the strength of her relationship.

  • • •

  ON NANTUCKET ISLAND off the coast of Massachusetts, where Maria Mitchell had made her world-renowned comet discovery in 1847, a small observatory commemorated her good name. The Maria Mitchell Association occupied the astronomer’s birthplace on Vestal Street and a domed structure next door to it. The association was founded in 1902, thirteen years after Miss Mitchell’s death, by her cousin Lydia Swain Mitchell, who had also been born in the house on Vestal Street. Cousin Lydia, now Mrs. Charles Hinchman, lived in Philadelphia with her husband and children, but returned to Nantucket every summer, and felt a duty to keep the spirit of astronomy alive on the island. She frequently consulted the director of the Harvard College Observatory for advice, and asked him to recommend guest lecturers. For several years beginning in 1906, Annie Jump Cannon made a summer pilgrimage to Nantucket in this capacity. She also taught a correspondence course in astronomy and helped bring Ida Whiteside of the Wellesley Observatory and Professor Florence Harpham of the College for Women at Columbia, South Carolina, to the island as “summer observers.” At “Moon Nights,” the public got to look up through Maria Mitchell’s own 3-inch comet-seeker and also the 5-inch Alvan Clark telescope purchased for her in 1859 by a group of admirers called the Women of America. The popularity of the Vestal Street activities gave Mrs. Hinchman the idea of awarding a yearlong stipend to a young lady who could conduct research at the observatory while instructing the locals in star lore. An appeal to Andrew Carnegie garnered $10,000 toward the goal. In 1912 Margaret Harwood, a Harvard computer, received the first $1,000 astronomical fellowship of the Nantucket Maria Mitchell Association.

  Miss Harwood had joined the Harvard staff in 1907, recruited from that year’s Radcliffe graduating class by her astronomy professor, Arthur Searle. Having boarded with Arthur and Emma Searle and their daughters since her freshman year of college, Miss Harwood was a familiar face at the observatory even before day one of her employment. At first she assisted Searle, whom she called her “father in astronomy,” by computing the orbits of comets. She helped Miss Leavitt assess the photographic magnitudes of circumpolar variables on the glass plates, and learned from Miss Cannon how to observe them by telescope. Pickering enlisted her aid in recalculating the positions of sixteen thousand stars catalogued by the Bonds in the 1850s.

  The Maria Mitchell Association invited Miss Harwood to carry on her research at Harvard for the first half of her fellowship year, and then transfer in June to Nantucket, where they accommodated her through December in an upstairs bedroom of the Mitchell residence. Downstairs in the museum proper, her housemates included collections of Nantucket flora and fauna, fossil displays, and a library about equally divided between astronomy and natural history topics. On Monday nights in the parlor she gave a lecture that spilled out onto the lawn or into the next-door observatory for stargazing. When Professor Pickering visited, he declared the site, remote from the smoke and glare of cities, ideally suited to the study of asteroids by photographic telescope, and the association raised the funds to purchase such an instrument. Miss Harwood so thoroughly endeared herself to the Mitchell family members and the Vassar alumnae who endowed her position that they all looked forward to her return for a second season in the summer of 1913.

  On another island, far south of Nantucket, William Pickering established a one-man observatory at Mandeville, Jamaica. William had first tested Jamaica as an observing site in 1899, when he repaired there for a family vacation and noticed a pleasant clarity in the air. In October 1900, after convincing his brother of Jamaica’s suitability as an outpost in the Eros campaign, William returned for a six-month stay with his family and a new telescope at a rented Mandeville estate named Woodlawn. Unfortunately, he failed to get good pictures of Eros. In an attempt to salvage the expedition, he remained at Woodlawn through August 1901, photographing the Moon for a lunar atlas that he later published.

  Over the next several years, while William maintained a base at Cambridge, he pursued the Moon and planets from sites in California, Hawaii, Alaska, the Azores, and the Sandwich Islands. In 1911, when his risky investments failed and ruined William financially, Edward helped him relocate temporarily to the familiar Woodlawn grounds. The 11-inch Draper refractor accompanied William to what he euphemistically termed the Harvard Astronomical Station in Jamaica. Woodlawn, once a thousand-acre plantation, owned an ideal telescope mounting site on a patio previously used to dry coffee beans. William’s $2,500 annual salary stretched further in the Caribbean than in Cambridge, and he pronounced the seeing at Mandeville the equal of Flagstaff’s or Arequipa’s. He could see no reason to leave. Thus the tropical Woodlawn estate became the Woodlawn Observatory, and William Pickering its astronomical lord of the manor. Isolated and increasingly eccentric, he spoke out as he pleased about the Martian canals, the green vegetation on the red planet, and the likelihood that Mars supported some kind of animal life.

  • • •

  MISS CANNON HAD CLASSIFIED one hundred thousand stars when she set the work aside to spend the summer of 1913 in Europe with her sister, Mrs. Marshall. They planned to attend three major astronomy meetings on the continent, plus all the banquets, garden parties, excursions, and entertainments that such international congresses entailed. On her previous trip to Europe, with her friend and Wellesley classmate Sarah Potter in 1892, Miss Cannon had made the grand tour of popular tourist destinations, camera in hand. This time she would go as a respected astronomer and the only female officer in her professional organization. At the 1912 meeting of the Astronomical and Astrophysical Society of America, the members had voted to change their name to the American Astronomical Society and to make Miss Cannon their treasurer. Now she would seek out her foreign colleagues, many of whom she knew only by reputation or correspondence, in their native settings.

  “There are no women assistants,” Miss Cannon noted of the Royal Observatory, Greenwich. Travel broadened her appreciation for the singularity of Harvard’s large female staff, although she easily befriended men wherever she went. At Greenwich, “Without the slightest feeling of being out of place, without the smallest tinge of embarrassment, I discussed absorbing work with one and another.” That evening the astronomer royal, Frank Dyson, called for Miss Cannon and Mrs. Marshall at their London hotel and escorted them to a soiree at Burlington House, the headquarters of the Royal Astronomical Society and four other scientific fraternities. “Never has it been my good fortune to have such a kindly greeting, such hearty good will, such wonderful feeling of equality in the great world of research as among these great Englishmen.” At the society’s meeting a few days later, she gave a formal presentation about her recent investigation into the spectra of gaseous nebulae.

  Mrs. Marshall understandably avoided the scientific sessions, at which Miss Cannon inured herself to being the sole woman in a roomful of as many as ninety men. In Germany, she reported, “Not a single German woman attended these Hamburg meetings” of the Astronomische Gesellschaft. “Once or twice, two or three would come in for a few minutes but I was generally the only woman to sit through a session. This was not so pleasant but at the recesses the men were so kind that nothing seemed to matter, and at the luncheon women appeared in great numbers.”

  In Bonn, where the Solar Union gathered from July 30 to August 5, the astronomers were treated to a flyby visit of a military zeppelin, a side trip to the Gothic cathedral at Cologne, a riverboat ride up the Rhine, and a gala night in the Bonn observatory that prompted the E
nglish-speaking delegates to sing “They Are Jolly Good Fellows” to Director Friedrich Küstner and his wife and daughters. “Luncheon and indeed all meals in Germany,” observed Canadian astrophysicist John Stanley Plaskett, “are a much more important and solemn function than with us and take at least twice the time.”

  Pickering, an elder statesman in this community, spoke at several banquets during the week. He shared impressions of his previous stays in Bonn, a city he had long regarded as the world capital of photometry. It was here that the legendary Friedrich Wilhelm Argelander assembled the Bonner Durchmusterung star catalogue and perfected the Argelander method of studying variables by comparing them to their steady neighbors. Argelander’s own small telescope, still mounted at the Bonn observatory, proved an object of veneration for the visiting astronomers.

  Only about half the members of Pickering’s Committee on Spectral Classification, first convened at Mount Wilson, had come to the Bonn meeting. Those present included Henry Norris Russell, Karl Schwarzschild, Herbert Hall Turner, and of course Küstner, of the local observatory. They met Thursday afternoon, July 31, to polish their report before Friday’s discussion and vote. The group had considered incorporating some symbols into the Draper classification that would account for the widths of spectral lines, but ultimately rejected the idea. Rather than retrofit the Draper system, they preferred to look forward and explore the possibility of an entirely new design for stellar taxonomy.

  On Friday morning Chairman Pickering read the committee’s recommendation to the full assembly at the Physical Institute. He proposed postponing “the permanent and universal adoption” of any system until the committee could formulate a suitable revision. In the interim, however, everyone should foster the well-known and widely praised Draper classification. Approval of the resolution was swift and unanimous. Ditto the subresolution regarding a refinement originally suggested by Ejnar Hertzsprung and already practiced by Miss Cannon. It consisted of a zero subscript for lone letters. Going forward, A0 would denote a star of purely A-category attributes, showing no B tendencies whatever. The new A0 reduced plain A to a “rough” categorization.

  At the final session on August 5, the Solar Union dissolved its old committees and regrouped into new ones for the work to be done over the next three years, before they would all meet again in Rome.

  “When the names of committees were read,” wrote Miss Cannon, “I was very much surprised to find that I was put on the Committee on Classification of Stellar Spectra—and one of the novel experiences of the summer was to meet with this Committee. They sat at a long table, these men of many nations, and I was the only woman. Since I have done almost all the world’s work in this one branch, it was necessary for me to do most of the talking.”

  CHAPTER TEN

  The Pickering Fellows

  YEAR-END HOLIDAY GREETING CARDS from the Harvard College Observatory in 1913 featured a single gold star, with a word at each point naming the five stellar data: position, motion, brightness, spectrum, and color. On Miss Cannon’s card, Professor Pickering penned in his personal best wishes “for a Merry Classification and a Happy New Type of Spectrum.” Miss Cannon was classifying or reclassifying approximately five thousand stars per month. Along the way she reinstated two of Mrs. Fleming’s categories, N and R, putting R ahead of N. The alphabetical disorder of her system was ultimately conquered by a new mnemonic: Oh, Be A Fine Girl, Kiss Me Right Now!

  Astronomers from all over Europe and the United States, while awaiting publication of the revised Draper catalogue, often queried Miss Cannon about the spectrum of particular stars for their studies. One of her many regular correspondents, Herbert Hall Turner of Oxford, tendered his congratulations on March 13, 1914, regarding an honor “unanimously and cordially” conferred on her that very day. She received no official notice, however, until early May, when an embarrassed Arthur Stanley Eddington, secretary of the Royal Astronomical Society, apologized to Miss Cannon for the oversight.

  “A form of Diploma is being prepared, which you will receive before long,” Eddington promised, “but, of course, it was intended that you should be informed at once. The mistake seems to have been due to a misunderstanding between the President [Edmond Herbert Grove-Hills] and myself as to which one of us had undertaken the letter. Our best excuse is that the election of an Honorary Member is so rare an occurrence that we have no routine way of procedure, so that mistakes are not provided against.” Eight years had passed since Mrs. Fleming’s election, and by 1914 all the previous honorees, save for Lady Margaret Huggins, had passed on.

  Miss Leavitt’s work likewise drew wide attention, though not the formal accolades of the kind Miss Cannon reaped. Nor did Miss Leavitt travel to international gatherings, but remained at the observatory, sometimes in a supervisory capacity when other officers were away. Bailey, who often played that role, commended her fitness for it, with her nature “full of sunshine” and her ready perception of everything “worthy and lovable in others.”

  The stars that had led Miss Leavitt to her period-luminosity relation were called Cepheids, for the group archetype, Delta Cephei, in the constellation Cepheus, the King.* John Goodricke of England was the first, in 1785, to describe Delta Cephei’s pattern of variation—the sharp rise and slow ebb of brightness that proved characteristic of variable stars in other constellations as well. Some thirty Cepheids were known in the 1890s, before Solon Bailey began discovering scores more in the star clusters of the Southern Hemisphere. Later Miss Leavitt made their number legion. By mid-January 1914, when she had finished counting the variables in her third of the sky and concluded her many years of work on the North Polar Sequence, the Cepheids were beckoning new followers.

  Harlow Shapley, a young American astronomer completing graduate studies under Henry Norris Russell at Princeton, visited Harvard in March 1914. Pickering welcomed him in typical fashion, offering to provide any materials from the observatory that he wanted. Miss Cannon took him home to dinner, and when he went to call on Solon Bailey, upstairs by the observatory dome, he received advice that shaped the course of his career.

  “Bailey was pious and kind, a wonderful sort of man,” Shapley later rhapsodized, “but so New England it made you ache.” Shapley came from rural Missouri, and had worked as a crime reporter for a Kansas daily before pursuing his higher education. According to Shapley’s account of their conversation, possibly recorded in newspaperman’s shorthand, Bailey said, “I hoped you wanted to come up here; I have been wanting to ask you to do something. We hear that you are going to Mount Wilson. When you get there, why don’t you use the big telescope to make measures of stars in globular clusters?” Few besides Bailey found these stellar swarms appealing, and Bailey himself lacked access to a telescope large enough to probe them deeply, either from Cambridge or from Arequipa.

  As often as Shapley could gain his own observing time on Mount Wilson’s 60-inch reflecting telescope, he did as Bailey requested. “Within a month or two after I got to Mount Wilson,” Shapley recorded in a memoir, “Shapley and the globular clusters became synonyms.” In the clusters he found new examples of Miss Leavitt’s stars. Soon he developed a theory about their nature: The Cepheids were not closely orbiting pairs, as most astronomers believed, but enormous, isolated individuals. He could claim as much because their sudden surges in brightness seemed to indicate outbursts of some kind, not a pattern of eclipses by a partner star. The Cepheids owed their variation, Shapley hypothesized, to dramatic pulsations in temperature and diameter. He described them as “throbbing or vibrating masses of gas.”

  A number of new Cepheids found by Shapley displayed the long periods indicative of great brightness according to Miss Leavitt’s law. These gave Shapley a way to ascertain their positions and the distribution of the clusters in space. He adapted the techniques Ejnar Hertzsprung had used for deducing distances from period and magnitude, and began measuring the way out to some of the hundred clusters he could see.
He noticed a group of them—a “cluster of clusters”—huddled together in a section of the Milky Way, near the constellation Sagittarius, the Archer. He wondered what was so special about that particular area.

  • • •

  THE OUTBREAK OF THE GREAT WAR in Europe hobbled astronomy there and placed a new imperative on the United States, as Pickering saw things, to sustain all fields of scientific research. He found himself in what seemed an ideal position to aid fellow scientists, as the recently appointed executive chair of the new Committee of 100 on Research, established in 1914 by the American Association for the Advancement of Science. His efforts got off to a bad start, however, when his early official appeals on behalf of four physics and astronomy projects failed to win funding from the Carnegie Institution.

  As for the needs of his own institution, Pickering never tired of reminding President Lowell that Harvard contributed nothing to the observatory’s support. Fear of fire still fueled the director’s oft-repeated plea for more brick structures to replace the wooden ones, and he sighed with relief every time a manuscript series of observations found permanence in a published volume of the Annals. For several years up to and including 1914, expenses had exceeded income, forcing Pickering to curtail activities. In December 1914, however, the observatory received a large new sum under regrettable circumstances.

  “During the last year,” Pickering wrote in his annual report, “the Observatory has lost, by the death of Anna Palmer Draper, its most generous benefactor.” She had died at home in New York, of pneumonia, on December 8. “It rarely happens that a woman maintains for many years a great scientific enterprise, and by monthly subscriptions shows her unfailing interest in it. Mrs. Draper for nearly thirty years supported the Henry Draper Memorial, and by her will placed it upon a permanent foundation.”

  The terms of Mrs. Draper’s will promised the observatory the sum of $150,000, in addition to the quarter million she had already given, “for the purpose of caring for, preserving, studying and using the photographic plates of the Henry Draper Memorial.” Anticipating a lengthy probate, Mrs. Draper had instructed her executors to pay the observatory $4,000 the year of her death and $5,000 every year thereafter until her estate was settled, so the work of the memorial could continue uninterrupted. An article in the New York Times on December 20 about her several bequests mistakenly identified her husband as a former professor of astronomy at Harvard. She had willed her country house in Dobbs Ferry to a nephew on the Palmer side, and although she left legacies to niece and nephew Carlotta and Draper Maury, she made no allowance for their older sister, Antonia.