The Day We Found the Universe (18 page)

Henrietta Leavitt's historic 1912 graph showing how a Cepheid's
brightness increases as the variable star's period gets longer
(From
Harvard College Observatory Circular,
No. 173
[
1912
]
, Figure 2
)

Cepheids stood ready to be the perfect standard candles, but first she needed to know the
true
brightness of at least one, the luminosity she would observe if she were essentially right next to the star. If she could determine the brightness of just one, her graph would let her know all the others. Once her graph was calibrated in this way, an astronomer could pick out a far-off Cepheid anywhere in the sky, measure its period, and infer its actual luminosity. The distance to the Cepheid then followed: By measuring the Cepheid's
apparent
brightness in the sky (a much fainter magnitude), you could figure out how far away it must be to appear that dim. Cepheids held the promise of being astronomy's handiest cosmic measuring tape. Astronomers could at last gauge the distance to celestial objects farther out than they ever conceived possible. Leavitt knew this, but she wasn't one to state things so daringly. Besides, Pickering chose his women computers “to work, not to think,” according to one Harvard astronomer. So, in a far quieter tone, Leavitt simply wrote at the close of her paper, “It is to be hoped, also, that the parallaxes [essentially, distances] of some variables of this type may be measured.”

What was needed was an indisputable distance to a bona fide Cepheid. But Leavitt's going to a telescope to pursue an answer was out of the question, not only because women were denied access to the best telescopes at the time (generally considered man's work) but because of her frail condition. Given her deafness and frequent illnesses, she had been advised by her doctor to avoid the chilly night air, an environment habitually faced by observers. She came to believe the cold aggravated her hearing condition. If she had the know-how, she could have carried out a calculation from her desk, using stellar data from previously published work, but Pickering held the strong conviction that his observatory's prime function was to collect and classify data, rather than apply it to solve problems. The accumulation of facts was Pickering's prime directive, so he quickly assigned Leavitt another task, a project on stellar magnitudes that he considered far more important. She respectfully carried out her boss's directive without objection for a number of years. Back in her room at the observatory, she continued to work on the stars photographed by others. Cecilia Payne-Gaposchkin, who came to the Harvard Observatory in the 1920s, called this “a harsh decision, which condemned a brilliant scientist to uncongenial work, and probably set back the study of variable stars for several decades.” Yet Leavitt's effort was not wasted. In the end her delegated work served as the basis for an internationally accepted system of stellar magnitudes.

But her desire to pursue the variables never left her; it only awaited the proper time to act on it. Soon after Pickering's death, Leavitt at last divulged her most cherished interest to the observatory's new director, Harlow Shapley. Once he arrived at Harvard in 1920, she lost no time in asking his advice on advancing her research on the stars in the Magellanic Clouds. By then Shapley had already calibrated the Cepheids, but he told Leavitt he would like to see a deeper investigation of the short-period variables, stars that pulse over a matter of hours instead of many days. “[It's] of enormous importance in the present discussions of the distances of globular clusters and the size of the galactic system,” he said. Moreover, does the same period-luminosity law also work for stars in the Large Magellanic Cloud? he asked. He wished her success on tackling these questions.

But just as she was on the verge of completing her prolonged stellar magnitude project—possibly when she would have at last gone back to her work on the Cepheids—Henrietta Leavitt passed away at the age of fifty-three. She had faced a long and grueling struggle with stomach cancer. By the time of her death, on December 12, 1921, she had discovered some twenty-four hundred variable stars, about half the number then known to exist. Her contributions at Harvard had been unique, making it difficult for them to replace her. “Miss Leavitt had no understudy competent to take up her work,” Shapley told a colleague the day after her death. Unaware of her passing, a member of the Royal Swedish Academy of Sciences four years later contacted the Harvard Observatory to inquire about her discovery, intending to use the information to nominate her for a Nobel Prize in Physics. But by the rules of the award, the names of deceased individuals could not be submitted.

Empire Builder

I
n 1914 the world was plunged into turmoil as the Allied and Central powers rapidly faced off in the War to End All Wars, the four-year conflict that demolished old empires and reshaped the modern world. And yet, in this time of devastating upheaval, astronomy experienced some of its greatest discoveries. Vesto Slipher was measuring the fleeing spirals, Heber Curtis was ferreting out new ones, and Harlow Shapley was gearing up to move our Sun from its hallowed position at the center of the known universe. While the landscape of global politics was being redesigned, so too was our cosmos.

The Milky Way had long been pictured as relatively small, at most around 20,000 to 30,000 lightyears wide (estimates at this time varied), but in 1918 Shapley radically increased our galaxy's girth to some 300,000 lightyears. Moreover, he declared that our solar system was situated a good 65,000 lightyears from the galaxy's heart. Barely recovered from its Copernican shift from the center of the solar system, Earth was demoted once again. The Milky Way's overall width was later amended, adjusted downward to some 100,000 lightyears when better calibrations were undertaken, but even then it was far vaster than anyone had previously imagined.

Shapley would never have had this opportunity were it not for the astounding foresight and boundless fortitude of George Ellery Hale. A noted solar astronomer, Hale discovered that there were magnetic fields in sunspots, a sensational finding in its day, for it was the first magnetic field detected beyond Earth. He also cofounded the
Astrophysical Journal
(along with James Keeler) and helped transform the Throop College of Technology into the California Institute of Technology. But Hale made his most valuable contributions to astronomy as an administrator. It was largely through his focused efforts over several decades that America wrenched the baton from Europe in astronomical leadership. Hale nearly single-handedly orchestrated the construction of four great telescopes in the United States, each larger and more advanced than the one before. In carrying out this colossal endeavor, he allowed Shapley to revamp the Milky Way and the astronomers who followed to reveal the true vastness of the universe and the amazing diversity of its celestial inhabitants. Astronomer Allan Sandage of the Carnegie Observatories is convinced that astronomers “owe
all
to Hale and his dreams and positive actions to put those dreams into glass and steel. Where would world astronomy be today if Hale had not been an ‘empire builder’?”

Hale took unique advantage of the magnificent productivity of his era. It was once jokingly noted that American astronomy became preeminent at this time because of two discoveries: Pickering discovered women and Hale discovered money. American industrialists were amassing great fortunes, capital that was just waiting to be tapped for philanthropic undertakings in an era before the federal income tax was permanently established. Of all the sciences in the Gilded Age, astronomy was the most popular destiny for private support in the United States. One reason is that astronomy held out the promise of a shiny white dome on a mountain, for all to look up and admire. Hale, too, commented that the public regards “astronomical research with a feeling of awe which is not accorded to other branches of science [because of] its power of searching out mysterious phenomena in the infinite regions of space.”

Hale himself was the very personification of this union of money with science at the turn of the twentieth century. Hale's father, William, had secured sizable riches as the manufacturer of hydraulic elevators, produced for the many skyscrapers that began to dot the Chicago urban landscape after the Great Fire of 1871. His company also supplied them for Paris's Eiffel Tower. Some of the capital from these enterprising ventures offered Hale as a teenager sufficient funds to construct his own spectroscopic observatory in the attic of the family mansion in the Hyde Park section of Chicago, where he avidly studied the Sun's spectrum, alongside his books, laboratory equipment, and fossil collection. He was a precocious boy with a formidable power of concentration—always curious and always devising new ways to study the natural world. He chose the Sun as his target of interest because, as the closest star, he hoped it might better reveal the secrets of stellar evolution. Shortly after his twentieth birthday in 1888, he confirmed that the element carbon resided in the Sun, a matter then in great debate. Before Hale even graduated from college, he developed a new instrument—the spectroheliograph—that enabled astronomers to photograph the surface of the Sun and its fiery prominences as never before. It imaged the Sun in one chosen wavelength of light, a spectral band being emitted by a specific chemical element of interest. Science was still reeling in the late 1800s from the magnificent discoveries in geology and biology that so beautifully demonstrated the gradual changes that occurred over Earth's history: new species evolving and landscapes continually sculpted by natural forces. Hale was seeking evidence of a similar dynamic within the universe itself.

Upon graduating from the Massachusetts Institute of Technology, class of 1890, Hale married his childhood sweetheart, Evelina Conklin, and took an extended honeymoon trip to Niagara Falls, Colorado, San Francisco, and Yosemite. But he was most excited, while out in California, to get a personal tour of Lick Observatory. There, he had the opportunity to work one night with James Keeler, as the Lick astronomer was observing planetary nebulae. Hale was mightily impressed and never forgot his first glimpse of the 36-inch refracting telescope, then the world's largest, its long tube “reaching up toward the heavens in the great dome,” he later recalled. Hale primarily studied the Sun, Keeler the stars and nebulae, but both were fervent advocates of spectroscopy. They became fast friends.

Within two years of his return to Chicago, Hale became an associate professor at the newly reorganized University of Chicago. With the university's promise of future funding for a larger telescope, he allowed the university to use his personal observatory, grandly christened the “Kenwood Physical Observatory.” The complex was built right next door to the Hale family mansion and housed both a 12-inch refractor, paid for by his father, and his revolutionary spectroheliograph. “I would not consider [joining the faculty]
for a moment
were it not for the prospect of some day getting the use of a big telescope to carry out some of my pet schemes,” he told an acquaintance.

That prospect arrived sooner rather than later, due solely to Hale's resourcefulness. After attending the latest meeting of the American Association for the Advancement of Science in Rochester, New York, in the summer of 1892, he went out to cool off on his hotel's veranda and overheard a conversation about two 40-inch telescope lenses that had unexpectedly become available. The glass disks had been made for a planned observatory in southern California that was aimed at surpassing Lick in telescopic power. A real estate boom had brought sudden wealth to the Los Angeles area, and for the sake of regional pride developers were eager to erect their own grand astronomical monument—until the promoters went broke when the land bubble burst. For Hale, so eager to acquire a large telescope for his solar investigations, ready access to such lenses was a stroke of luck. A lens forty inches wide had nearly 25 percent more surface area than the Lick's 36-inch lens and so would gather 25 percent more light, a huge and treasured gain for any astronomer. Given the brush-off by a bevy of Chicago's wealthiest businessmen to sponsor the purchase of the lenses, Hale at last convinced Chicago's streetcar magnate, Charles Tyson Yerkes, to fund construction of the giant instrument. Hale's work as an astronomer provided the scientific arguments for this bold step; his family's wealth and position gave him the self-confidence, even though he was only twenty-four years old, to win over Yerkes in financing such a grand scheme.