The Glass Universe

by Dava Sobel

  The following month gave both Pickering and Miss Bruce genuine cause for shared happiness. “I hold out my hand to grasp yours,” she effused on September 9, when she heard that the lenses for the large photographic telescope had passed their first examination. “Let us rejoice.”

  In October, as though in atonement, William resumed photography at Arequipa for the Henry Draper Memorial. By the end of December 1892 he had shipped two thousand plates to Cambridge.

  • • •

  ALMOST FROM THE MOMENT stars began amassing on Harvard’s glass photographic plates, the director developed a dread of their destruction by fire. The larger the collection grew, the more devastating the contemplation of its loss, should the wooden observatory building ignite. Virtually everyone of Pickering’s acquaintance had lost something of value to a conflagration. Mrs. Draper’s family, for one, owned a theater in Union Square that burned to the ground in 1888, and its reconstruction continued to cause her grief. Consequently she had become something of an expert on fireproof paint, periodically urging its application to the observatory.

  Pickering favored an alternate solution. In 1893 he announced the completion of a two-story “fire-proof building,” made entirely of brick, for the safe storage of glass plates and manuscripts of yet-to-be published results. The Brick Building, as everyone soon came to call it, crowned Pickering’s fifteen years of site improvements, from the numerous telescope domes and sheds to the neighboring house on Madison Street that had been transformed into a photography workshop and darkroom. In the words of journalist Daniel Baker, whom Miss Bruce commissioned to write up the observatory’s history, the hilltop once dominated by a single edifice had become a “little city of science.”

  Mrs. Fleming oversaw the packing of the thirty thousand plates into three hundred crates. On March 2, 1893, workers rigged a block and tackle from the roof of the observatory’s west wing to a window of the new repository. Then they slid the approximately eight tons of plates down the rope skyway at the rapid clip of a crate per minute. Despite the precarious flight, not one piece of glass cracked or shattered.

  Naturally Mrs. Fleming and most of the computers followed the plates into the new space, to remain close to them. They traveled at ground level by a wooden walkway over the muddy intervening ditch. When Miss Maury returned to join them in the spring, Pickering asked for her promise to complete her classification before the end of the year or turn over the work to someone else, and she signed a statement saying that she would.

  There were now seventeen women computing at the observatory. In other words, nearly half of the observatory’s forty assistants were female—a fact Mrs. Fleming intended to emphasize in her invited remarks for the upcoming Congress of Astronomy and Astro-Physics in Chicago.

  The name of the congress called attention to astronomy’s increasing emphasis on the physical nature of the stars through spectroscopy. Some self-styled astro-physicists were already distancing themselves from the more traditional observers who concentrated on stellar positions or cometary orbits. George Ellery Hale trumpeted the new trend. He had been briefly associated with Harvard while a student at MIT, before establishing his own Kenwood Observatory in his native Chicago in 1890. It was Hale who prevailed upon the editor of the Sidereal Messenger to change the publication’s name to Astronomy and Astro-Physics in 1892. And it was again Hale who organized the August 1893 Congress of Astronomy and Astro-Physics. By timing the meeting to coincide with the Chicago World’s Fair, or Columbian Exposition, he added incentive for astronomers from either coast and other continents to undertake the journey.

  Hale invited Pickering to present the opening address to fellow scientists at the conference, as well as a broader, less technical talk to inform the fair-going public about the fabric of the stars. Hale also requested an exhibit’s worth of photographs documenting the work of the Harvard College Observatory and its physical plants in Cambridge and Arequipa. Pickering included photographs of the women at work in the new Brick Building.

  Pickering began preparing the text for his popular address well in advance. “Our only knowledge of the constitution of the stars,” it began, “is derived from a study of their spectra.”

  Mrs. Fleming also prepared an invited paper for the Astronomy and Astro-Physics congress. The previous summer in Chicago had seen the two women’s rights federations merged into one “National American Woman Suffrage Association.” This year, soon after the Exposition opened in May 1893, suffragettes Julia Ward Howe and Susan B. Anthony had made impassioned presentations. Though Mrs. Fleming fully affirmed the principle of equality, she was not an American citizen, and the feminist struggle for the right to vote was not her fight. The cause she championed was equality for women in astronomy: “While we cannot maintain that in everything woman is man’s equal,” Mrs. Fleming averred in her Chicago contribution, “yet in many things her patience, perseverance and method make her his superior. Therefore, let us hope that in astronomy, which now affords a large field for woman’s work and skill, she may, as has been the case in several other sciences, at least prove herself his equal.”

  The White City of the Columbian Exposition, with its two hundred grand structures, held numerous fascinations for Anna Draper, who visited the fair in mid-June. The Woman’s Building had been designed by Sophia Hayden, the first of her sex to receive a degree in architecture from MIT, and its interior bore murals and paintings executed by well-known female artists such as Mary Cassatt. Other not-to-be-missed highlights included the Electricity Building’s seventy-foot-tall tower of lightbulbs and the Hall of Agriculture’s fifteen-hundred-pound copy—in chocolate—of the Venus de Milo. Inside the Manufacturers’ Building, Mrs. Draper stared up at the mammoth mounting pier and tube of a new telescope that would soon move to a permanent home on the shores of Lake Geneva in Wisconsin. The tube stood empty. Its 40-inch object glass—the very monster that had vied with the Bruce lens for priority in Mantois’s Paris establishment—still lay hundreds of miles back East, on the lathe at Alvan Clark & Sons.

  By late summer, progress on the Bruce telescope had reached a critical stage. Only William Pickering was free to represent the Harvard Observatory at the astronomy conference in Chicago. When Mrs. Fleming’s speech was read aloud for her at the session held Friday, August 25, William seconded her statements in praise of the efficient women’s force in Cambridge. The next day he presented his own report, titled “Is the Moon a Dead Planet?,” in which he answered his own question with an emphatic “No.”

  In early September the first piece of giant iron superstructure for the Bruce telescope made its slow way up Summerhouse Hill. Placement of the two-ton bed plate occupied six men and four horses for a full day. Edward Pickering watched the “ponderous affair” of assembly wear on for two more months before he got the proof he needed to declare the whole grand giant-telescope enterprise entirely worthwhile.

  “We have obtained some remarkable photographs,” he wrote Miss Bruce on November 19. “I can now safely report its assured success, and can congratulate you on having the finest photographic telescope in the world.”

  CHAPTER FOUR

  Stella Nova

  NOTHING IN THE SKY SURPRISED an astronomer more than the sudden apparition of a new star where none had been seen before. When the legendary Tycho Brahe of Denmark glanced skyward one night and beheld such a sight, he declared it “the greatest wonder that has ever shown itself in the whole of nature since the beginning of the world.” De nova stella, Tycho’s eyewitness account of the 1572 marvel, argued that Aristotle had been wrong to call the heavens immutable. Surely the abrupt appearance of the new star and its subsequent disappearance a year later proved that change could occur in the realm beyond the Moon.

  Not long after Tycho died in 1601, another nova burst into splendor. Both Galileo in Padua and Johannes Kepler in Prague observed the brilliant new star of 1604, which was so bright as to be visible in the daytime for more than
three weeks. Although no comparable naked-eye nova ever materialized over the following centuries, a few fortunate astronomers who happened to be pointing their telescopes to the right place at the right time discovered seven more novae between 1670 and 1892. Then Mina Fleming found one. On October 26, 1893, while hunched over her light lectern with a magnifying glass during a routine perusal of a photographic plate newly arrived from Peru, she seized on a star with the peculiar spectrum unique to a nova—a dozen prominent hydrogen lines, all of them bright.

  The director cabled the exciting news to Solon Bailey, who had taken the photograph more than three months earlier, on July 10. Pickering hoped new pictures by Bailey would disclose what, if anything, remained of the nova. Meanwhile Mrs. Fleming looked back in time through the plates to see what had preceded it, but found no trace in prior photographs of the same region. The star must have been dim indeed before its leap from obscurity to seventh magnitude.

  The nova lay in a constellation defined and named in the mid-eighteenth century by Nicolas Louis de Lacaille, a French astronomer, on a voyage south. Where others might have seen beasts or deities, Lacaille perceived fourteen instruments of modern science, from Microscopium and Telescopium to Antlia (air pump) and Norma (originally Norma et Regula, for the surveyor’s square and rule). Now, thanks to Mrs. Fleming, the small, inconspicuous Norma gained fame as the home of the first nova to be detected by spectral photography. It was only the tenth such star to have been observed in recorded history, and it was hers.

  Nova Normae’s most recent predecessor, the new star of 1891, had been espied visually through the telescope of an Edinburgh amateur, who alerted the Scottish astronomer royal by anonymous postcard. The timely aviso allowed observatories in Oxford and Potsdam to photograph the nova within days of its discovery. Now Pickering placed a picture of that nova’s spectrum next to Nova Normae’s. The two were virtually identical. Together, they made the ideal illustration for the announcement of the new discovery “by Mrs. M. Fleming,” which Pickering submitted in early November to Astronomy and Astro-Physics. “The similarity of these two new stars is interesting,” he pointed out in his article, “because if confirmed by other new stars it will indicate that they belong to a distinct class resembling each other in composition or physical condition.” Even more important, their similarity had enabled Mrs. Fleming to make the discovery, and might lead her to others as she continued sifting through the spectra collected for the Henry Draper Memorial.

  Pickering regarded the nova—any nova—as the ultimate variable star. Novae figured first among the five types of variables he defined. Just as astronomers had divided the multitudes of stars into color or brightness or spectral categories in the ongoing effort to comprehend their nature, so, too, the rarer variable stars could be grouped by their behavior. A nova, a “new” or “temporary star,” flared and faded just once in a lifetime. Its brief glory thus distinguished Type I from the “long-period” variables of Type II, which underwent the slow, cyclical changes of one or two years’ duration, monitored by Pickering’s volunteer amateur corps. Type III experienced only slight changes, not easily followed via small telescopes; Type IV varied continuously in short time spans; and Type V revealed themselves to be “eclipsing binaries,” or pairs of stars that periodically blocked each other’s light.

  One could only wonder at the cause of a nova’s rapid rise to brightness. Something—a stellar collision, perhaps?—made the star release and ignite enormous quantities of hydrogen gas. The spectra of the two recent novae presented perfect portraits of incandescent hydrogen. Had Pickering become aware of the outburst sooner, instead of fifteen weeks after the fact, he might have tracked Nova Normae through its slow decline, watching the bright lines fade to dark, and the spectrum resume the semblance of a normal star.

  • • •

  SOLON BAILEY SUFFERED NO REMORSE at not having noticed Nova Normae himself. He had been entrusted with the day-to-day operation of the Arequipa station, the nightly rounds of photography, and the timely transfer of photographic plates to Harvard. Although he looked at every image to make sure it passed muster, the detailed scrutiny fell, as always, to the Cambridge staff of assistants and computers. He gladly added his voice to the chorus of congratulatory wishes now surrounding Mrs. Fleming.

  Since Bailey’s return to Arequipa in late February 1893, he had grown enamored of the great globular clusters of stars visible in the pristine southern skies. These objects, each a mere fuzz patch or hazy star to the unaided eye, appeared through a field glass as globes of nebulous light, dense at the core and fading gently toward the borders. Viewed through the 13-inch Boyden telescope, such clusters resolved into swarms of stellar bees. The abundance of individual components challenged Bailey to take a census of their populations. He began by capturing a single cluster in a two-hour exposure made the night of May 19, 1893. On a separate glass plate he ruled lines to produce a grid of four hundred tiny boxes. Laying the grid over the glass negative, and placing the pair under a microscope, he counted the stars in each compartment. “The cross-hairs of the eyepiece divided each square into four sub-squares,” he reported to Astronomy and Astro-Physics in June, “which served to prevent confusion in counting.” Even so, he asked Ruth Bailey to count, too, for confirmation. When he saw that his wife’s tally somewhat exceeded his own, he averaged their results to arrive at a total of at least 6,389 stars in the cluster called Omega Centauri. “There can be no doubt, however,” he added, given the difficulty of assessing the closely packed center, “that the whole number of stars comprising this splendid cluster is very much greater.” Then he proceeded to gauge the brightness of the individual cluster members, one row at a time, by comparing each star to its neighbors, in sequence—8.7, 9.5, 8.8, 8.5, 9, 8.8, 9.2, and so on.

  Bailey thought he might devote his life to the study of clusters, but not at the expense of his regular duties. He kept up the steady flow of chart plates and spectra plates. He outfitted a new meteorology station—the world’s highest—at the summit of El Misti with the help of his older brother, Hinman. Their younger brother, Marshall, disaffected by the exhausting work of the initial Peruvian expedition, had declined a second stint at Arequipa and enrolled instead in the College of Physicians and Surgeons in Baltimore.

  The globular clusters soon proved themselves fertile hunting grounds for variable stars. Mrs. Fleming picked out the first one in Omega Centauri in August, and Pickering found another a few days later. As these discoveries multiplied, a malcontent from within the Harvard ranks undermined their validity by attacking the observatory’s procedures.

  Seth Carlo Chandler, a variable star aficionado, had served under Pickering from 1881 to 1886 as a research associate and calculator of comet orbits. After leaving his post, he continued his affiliation with the observatory by helping to issue telegraph alerts of comet sightings and other time-sensitive information to the global astronomy community. In 1888 he released a catalogue of variable stars, complete with his own detailed numerical analyses of their variability. Like Pickering, he appreciated and encouraged the contributions of amateur volunteers to the study of variables, but he differed with the director on the best methods for discovering such stars. Chandler preferred the time-honored techniques of visual observing. Because he distrusted detections made via spectral photography, he omitted nearly all of Mrs. Fleming’s recent finds from his second variable star catalogue, published in 1893. Adding further insult in a supplement, he characterized more than a dozen of her discoveries as “alleged but unconfirmed.” Worse, in February 1894, in the respected international journal Astronomische Nachrichten, Chandler impeached the integrity of the entire Harvard Photometry study published in the observatory’s Annals. He cited fifteen “serious errors” in the monitoring of variable stars with Pickering’s meridian photometer. In each of these cases, the magnitude listed for a given date conflicted with other reliable observers’ reports, or with the known pattern of the variable in questio
n, indicating that the photometer had been focused on the wrong star. Possibly the instrument was fatally flawed. If it never pointed reliably, then misidentification might be rampant, and the work worthless.

  A colleague of Chandler’s digested the charges for public consumption in the pages of the Boston Evening Transcript on March 17, 1894, asserting that “adverse statements so sweeping and from so well-known an authority as Dr. Chandler call for an explanation which shall be satisfactory to scientific men.”

  It was said of Pickering that he loved to discuss but refused to dispute. Forced to make some rejoinder, he wrote a brief letter to the Transcript’s editor, printed March 20. He called the attack “unwarranted,” adding that the questions raised in it were “scientific in their character” and therefore “unsuited to a discussion in a daily journal.” He promised a full reply “through the proper channels.” Meanwhile the press in New York and Boston continued to harp on the story.

  Mrs. Draper heard of the fracas firsthand from Pickering and also read all about it in the New York Evening Post. It struck her as ludicrous for Chandler to assail Pickering’s photometric work—work that had been rewarded with the gold medal of the Royal Astronomical Society, the Henry Draper Medal of the National Academy of Sciences, and the Benjamin Valz Prize from the French Academy of Sciences. In her opinion, Pickering’s achievements had excited Chandler’s jealousy.

  The May 1894 issue of the Nachrichten carried Pickering’s official response. He conceded that the fifteen variable stars pointed out by Chandler had indeed been wrongly identified in the Annals, but they were isolated and understandable instances. As for Chandler’s broader accusation, well, “It is somewhat as though it should be argued from a physician’s losing twenty percent of his cholera patients that he had been equally unfortunate in his general practice.”