The Glass Universe: The Hidden History of the Women Who Took the Measure of the Stars. Дава Собел
types, which he designated by Roman numerals. Secchi’s Class I contained brilliant blue-white stars such as Sirius and Vega, whose spectra shared four strong lines indicating the presence of hydrogen. Class II included the Sun and yellowish stars like it, with spectra full of many fine lines identifying iron, calcium, and other elements. Classes III and IV both consisted of red stars, differentiated by the patterns in their dark spectral bands.
Pickering challenged Mrs. Fleming to improve on this elementary class system. Whereas Secchi had sketched his spectra from direct observations of a few hundred stars, she would enjoy the advantage of the Henry Draper Memorial photographs, boasting thousands of spectra for her scrutiny. The glass plates preserved more faithful portrayals of the positions of Fraunhofer’s lines than drawings could ever provide. Also, the plates picked up lines at the far violet end of the spectrum, at wavelengths the eye could not see.
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MRS. FLEMING REMOVED EACH GLASS PLATE from its kraft paper sleeve without getting a single fingerprint on either of the eight-by-ten-inch surfaces. The trick was to hold the fragile packet by its side edges between her palms, set the bottom—open—end of the envelope on the lip of the specially designed stand, and then ease the paper up and off without letting go of the plate, as though undressing a baby. Making sure the emulsion faced away from her, she released her grip and let the glass settle into place. The wooden stand held the plate in a picture frame, tilted at a forty-five-degree angle. A mirror affixed to the flat base caught daylight from the computing room’s big windows and directed illumination up through the glass. Mrs. Fleming leaned in with her loupe for a privileged view of the stellar universe. She had often heard the director say, “A magnifying glass will show more in the photograph than a powerful telescope will show in the sky.”
Hundreds of spectra hung suspended on the plate. All were small—little more than one centimeter for the brighter stars, only half a centimeter for the fainter ones. Each had to be tagged with a new Henry Draper catalogue number, and also identified by its coordinates, which Mrs. Fleming determined using the millimeter and centimeter rules inscribed on the wooden plate frame. She read off these numbers to a colleague who sat beside her, penciling the information into a logbook. Later they would match the Henry Draper numbers to the stars’ existing names or numbers, if any, handed down from previous catalogues.
In the rune-like lines of the spectra, Mrs. Fleming read enough variety to quadruple the number of star categories recognized by Father Secchi. She replaced his Roman numerals, which quickly grew cumbersome, with Fraunhofer-style alphabetical order. The majority of stars fell into her A category because they displayed only the broad, dark lines due to hydrogen. The B spectra sported a few other dark lines in addition to those of hydrogen, and by her G category the presence of many more lines had become the norm. Type O bore only bright lines, and Q served her as a catchall category for peculiar spectra she could not otherwise pigeonhole.
Pickering applauded Mrs. Fleming’s efforts, even as he conceded the arbitrary, empirical nature of her classification. He predicted that in time, with ever more stars studied, the underlying reasons for the different spectral appearances would reveal themselves. Possibly different stellar temperatures were responsible, or different chemical blends, different stages of stellar development, or some combination of such factors—or something as yet unimagined.
In January 1887 Pickering hit on a way to enlarge some of the spectra from smudge-like traces to an impressive four inches by twenty-four. He astonished Mrs. Draper by sending her several examples. “It scarcely seems possible that stellar spectra can be taken which will bear the enlarging of those that you have sent me,” she wrote on January 23. “I wonder what Mr. Huggins will say when he sees them.” This question stimulated her to strengthen her support of the Henry Draper Memorial, which currently amounted to about $200 a month, by promising $8,000 or $9,000 per year in perpetuity.
There seemed no reason for Mrs. Draper to cling any longer to the dream of continuing her husband’s research herself. She thought it best to divest the Hastings observatory of his remaining telescopes, and donate the lot to Harvard. The largest, with its 28-inch-diameter mirror, would likely prove a significant aid in Pickering’s pursuits. Still she wavered. It had been one thing to part with the 11-inch-aperture refractor, now ensconced at Cambridge, but the 28-inch reflector preserved precious memories of her wedding day.
Henry had always preferred reflecting telescopes, which gathered light by means of a mirror in lieu of a lens, over refracting ones that could introduce spurious color effects. He had begun crafting his own mirrors right after medical school, and must have made a hundred in all, but the 28-inch was his great reflector. On November 12, 1867, the day after he and Anna exchanged marriage vows in her father’s living room, they went downtown together to shop for a glass disk—the kind used in skylights—large enough to form a mirror 28 inches across. They referred ever after to that excursion as “our wedding trip.” It took them years to grind and polish the disk to the desired curvature and apply the ultrathin coat of silver that transformed the glass into a perfect mirror.
The 28-inch reflector had enabled them to take their landmark first picture of the spectrum of Vega in 1872, as well as their unrivaled photograph of the so-called Great Nebula in Orion ten years later, and also their final series of stellar spectra images during the summer before Henry’s death. On one of those humid July nights, undone by overcast skies, the two of them had quit the observatory around midnight to retire. But as they neared their country house two miles away on Wickers Creek in Dobbs Ferry, they saw the clouds dissipating, so they turned the horses around and drove back to Hastings to resume their work. She remembered returning that way on numerous other occasions just to seize a few more hours—even long ago, when they thought they had all the time in the world.
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“MRS. DRAPER HAS DECIDED to send to Cambridge a 28-inch reflector and its mounting,” Pickering announced on March 1, 1887, in the first annual report of the Henry Draper Memorial. He praised the project’s benefactress for providing not only the instruments required for the project but also the means for keeping them actively employed by operators “during the whole of every clear night,” and for “reducing the results by a considerable force of computers,” and for publishing them as well. He hoped that other donors would follow her example by similarly endowing astronomy departments elsewhere with the means to function to their fullest.
In the spring of 1887, while Mrs. Draper negotiated with the Hudson River Railroad for a car to carry the 28-inch to Harvard, the observatory received another huge bounty—approximately $20,000, to be augmented by $11,000 annually—for the establishment of an auxiliary station on a mountaintop.
Pickering had been climbing mountains all his life. He began summiting in New England with youthful companions who called him “Pick” and even “Picky.” He later measured the heights of points of interest in New Hampshire’s White Mountains on solo treks with fifteen pounds of apparatus strapped to his back. In 1876, around the time he left the MIT physics department to direct Harvard’s observatory, he founded the Appalachian Mountain Club for fellow outdoorsmen, and served as its first president. Still an active member in 1887, he could well imagine the advantage of stationing a telescope at high altitude.
The source of the sudden windfall was the contested will of Uriah Boyden, an eccentric inventor and engineer who had received an honorary Harvard degree in 1853. When Boyden died in 1879, unmarried and childless, he allotted $230,000 to perch an observatory far above the atmospheric disturbances that plagued astronomers at sea level. Many noble institutions, including the National Academy of Sciences, vied for control of the Boyden estate, but Pickering convinced Boyden’s trustees that Harvard University was the most likely of the suitors to invest the money wisely, and the Harvard Observatory most fit to carry out the testator’s instructions. Triumphant after five years of polite wrangling, Pickering organized an exploratory expedition to the Colorado Rocky Mountains.
The Boyden Fund gave Pickering the means to hire his younger brother away from MIT. William, likewise a charter member of the Appalachian Mountain Club, thus became the director’s assistant and guide for the western reconnaissance. The brothers left Cambridge in June 1887 along with Lizzie Pickering, three junior volunteers from the observatory, and fourteen crates