Дава Собел – The Glass Universe: The Hidden History of the Women Who Took the Measure of the Stars (страница 12)

William had never been happier, never enjoyed better seeing—the astronomer’s term for atmospheric conditions. He loved the clear, still mountain air of the Andes that enabled him to resolve unprecedented fine detail on the surfaces of the Moon and planets. Although the solar system was not the focus of any Harvard program planned for Peru, the planets now absorbed William’s attention almost to the exclusion of photometry and spectroscopy. Despite his early devotion to photographic technique, William backslid into visual observing at Arequipa. The 13-inch Boyden telescope, with which he photographed the eclipse in California, had suffered some damage to its clock drive on the journey south, rendering it temporarily unfit for long-exposure photography. Until new parts were in place, William felt free to savor the view through the instrument. It had a reversible lens that rendered it equally fit for the eye or the camera. Even after the needed repairs to the 13-inch were completed, and it stood ready to photograph the spectra of the brightest southern stars, William preferred to peer through its eyepiece and sketch the landscape of Mars.

While William neglected his duty in Peru, Mantois in Paris honored other lens orders ahead of Harvard’s. Miss Bruce deputized J. Cleaves Dodge, an old family friend living in France, to visit the glazier in the hope of rousing him to action on her telescope.

“We are not in luck,” Miss Bruce told Pickering on October 1, 1891, “decidedly not— Accept my condolences. Here is another cause of delay— Before you see all those discs you will have discovered your first grey hair and I! I shall be in cool repose in Greenwood [Cemetery]. But read Mr. Dodge’s letter.”

The enclosure described a cordial, half-hour conversation in which M. Mantois explained to Mr. Dodge “the mysteries of Crown and Flint glass, which to manufacture and to manipulate, as he seems to do, one must be a real alchemist.” This was hardly an exaggeration. Telescope lenses required glass made from the highest-quality materials, mixed according to secret recipes, and heated for weeks at temperatures above one thousand degrees in guarded foundries. The terms “crown” and “flint” distinguished the two basic types of glass by the added quantities of lead in the latter. Used alone, either crown glass or flint glass yielded lenses that brought different wavelengths of light to different focal points, creating a jumble of color distortion known as chromatic aberration. United, however, crown and flint corrected each other. As Joseph von Fraunhofer demonstrated in the early nineteenth century, a “doublet,” formed by a convex lens of crown glass paired with a concave complement of flint glass, could bring the focal points into better alignment.

“The trouble in the making of the lenses,” Dodge’s report to Miss Bruce continued, “seems to be the numerous accidents that occur in the firing and baking of the very best specimens, and which no human intelligence can foretell.” Mantois had lost months to bad luck with a 40-inch lens commissioned by another university and could not yet say for certain when he might satisfy Harvard, willing though he was. Dodge reproduced a verbatim recital of the man’s plight: “M. Mantois said, ‘You see I am as interested as anyone in the completion of the work, for I am not paid anything till it is all finished, but I can only send that which is perfectly satisfactory. Besides I am constantly in a great state of anxiety as to the baking of the molds; I have tubes connected with my bed to warn me at night if the fires are cooling; and the falling asleep of one of the watchmen may cost me no end of trouble and expense.’” Dodge left Mantois’s establishment convinced that no other career in manufacturing “is attended with more chances of failure than this one of glazier for telescopes.”

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HAVING CLASSIFIED TEN THOUSAND STARS, Mina Fleming turned her organizational gift to the arrangement of the ever-multiplying glass plates. The myriad photographs filled many wooden chests shelves and cupboards in both the computing rooms and the library. She imagined they would soon exceed all available space in the observatory building. In the interim she filed them by telescope and by type—the chart plates that mapped each section of the sky, the group spectra, the individual bright spectra, the star trails, and so on—each one in a brown paper envelope, each envelope labeled by number, date, and other identifying details, all of which were repeated on index cards in a card catalogue. Rather than pile the plates in columns, she stood them on edge for easy access. Reason to revisit one or another stored plate arose daily as the assistants examined, measured, discussed, and performed computations upon each new batch of photographs. When, for example, Mrs. Fleming spotted a spectrum that struck her as characteristic of a variable star, she did not need to wait for future observations to confirm her hypothesis. The evidence of the past would bear her out in the now. She had only to consult her records to see which photographs included that portion of the heavens, then pull the relevant plates from the stacks and compare the star’s current state with all its previous manifestations.

“So you have, ready to hand and for your immediate use,” Mrs. Fleming pointed out in a summary of her method, “the material for which a visual observer might have to wait” a very long time, perhaps indefinitely. Moreover, the plates trumped any visual observer’s report, “for in the case of the observer, you have simply his statement of how the object appeared at a given time as seen by him alone, while here you have a photograph in which every star speaks for itself, and which can at any time, now or in the years to come, be compared with any other photographs of the same part of the sky.”

Early in 1891, after she had identified a new variable in the constellation of the Dolphin, and, with the director’s approval, published her finding in the Sidereal Messenger, two skilled observers from other institutions took it upon themselves to corroborate the discovery. Both contested her claim, declaring the star not variable. When those same two astronomers met to discuss their conclusions, however, they realized they had each been watching a different star, neither of which was in fact Mrs. Fleming’s star. “No such error,” she all but crowed, “could have occurred from the comparison of the photographic charts.”

Detecting new variable stars had become Mrs. Fleming’s forte. Although fewer than two hundred such inconstant lights were known when she joined the observatory staff, the decade of her employment flushed out a hundred more, of which she personally identified a score. She made her earliest finds while gauging magnitudes by the size of the speck a star created on a photographic plate, and then noting which specks changed size in subsequent pictures. Spectra gave her an easier means. Once she had familiarized herself with the spectral features of a few well-known variables, she could recognize similar traits in other stars, almost at a glance. For example, the presence of a few light hydrogen lines among the black ones signaled a variable star near the height of its brightness.

As Mrs. Fleming ferreted out new variables, she also kept a close watch on the old. The director was keen to monitor how the spectra of variable stars changed over time, and the ways that variations in brightness correlated with the appearance of the Fraunhofer lines.

In the spring of 1891, Mrs. Fleming noticed something unusual about the familiar variable called Beta Lyrae. Its changeable nature had been known for a hundred years, but now, looking at its magnified spectrum, she recognized the doubled lines signifying that Beta Lyrae belonged to the newly defined group of spectroscopic binaries—that this star was in fact two stars.

Miss Maury also took an interest in Beta Lyrae, even a proprietary interest, given that Lyra (the Harp) was a northern constellation, and she had charge of the approximately seven hundred brightest stars of the northern skies. Together with Pickering and Mrs. Fleming, she reviewed twenty-nine Draper Memorial plates that contained images of Beta Lyrae. Her analysis suggested this binary did not comprise identical twins, as was the case for Mizar and Beta Aurigae, but two stars of different classes, each varying at its own rate and for its own reasons. She began to frame a theory about the nature of their relationship.

Pickering had hoped to publish Miss Maury’s classification of the northern bright stars by the end of 1891, as a sequel to Mrs. Fleming’s 1890 “Draper Catalogue of Stellar Spectra.” Unfortunately, Miss Maury seemed nowhere near ready to release her results. Her two-tiered classification system, which addressed both the identity and the quality of the spectral lines, required a painstaking exactitude. Anything less would deny the complexity of the problem. Although her slow pace disturbed Pickering, he could hardly accuse her of slacking. She had taken on a second job as a teacher in the nearby Gilman School, while still pursuing her observatory work so assiduously that he feared she neglected her health. Mrs. Draper, too, grew impatient with her niece. After a visit to the observatory in early December, she wrote Pickering, “I do hope Antonia Maury will make an effort and finish more satisfactorily what she has in hand.”