Starlight Detectives

by Alan Hirshfeld

  In mid-1904, after initial testing with a solar telescope imported from Yerkes, the Carnegie Institution granted Hale $40,000 to build a larger version of the instrument. Again, no money was included for completion of the sixty-inch reflector. Hale pushed ahead with the solar research in the hope that the results would stimulate a larger infusion of funds. Once asked about his uncanny ability to procure private and institutional support for his work, Hale responded, “The gods bring threads to a web begun.”

  On December 20, 1904, a year to the day after his arrival in Pasadena, the threads arrived. Hale was ascending Mount Wilson when he was called to a trailside way station. Over a crackly telephone line, the mountain’s only direct link to the outside world, an operator read out a telegram from Washington, DC: the Carnegie Institution had just allocated the full request of $310,000 to establish and operate the Mount Wilson Solar Observatory, with explicit authorization to mount the sixty-inch reflector. Hale resigned from Yerkes two weeks later to take up his new directorial post. (Hale’s final visit to Yerkes occurred in 1932. On his way out, he stepped into the dome of the great refractor, doffed his hat, and uttered, “Noble instrument.”)

  The Monastery building on Mount Wilson, photographed in 1905.

  The following summer, the state-of-the-art Snow Solar Telescope, formerly in operation at Yerkes, was transferred to Mount Wilson. Its thirty-inch, motorized, flat mirror directed sunlight horizontally to a second flat mirror, which in turn illuminated an image-forming concave reflector of sixty-feet focal length. The six-inch-wide solar image could be viewed directly or photographed; alternatively, the light could be deflected into a stationary spectrograph, either for line analysis or to photograph the Sun’s disk at a chosen wavelength. Secured to a concrete footing, the spectrograph used by Hale was far larger than any designed to hang from the end of a movable telescope.

  In 1908, Hale built the world’s first solar tower telescope—essentially a vertical version of the Snow instrument, sixty feet tall—to mitigate the image-distorting effects of heat rising from the ground. Four years later came a 150-foot tower telescope, capable of projecting a sixteen-inch-wide image of the Sun. Its spectrograph was fully twenty times as precise as the unit Hale had used at his original Kenwood Observatory. With the various solar instruments, Hale determined that sunspots are centers of intense magnetism, the first sign of magnetic activity on another world and arguably Hale’s greatest discovery. His observations also provided a springboard toward an understanding of the temperature-based variance of stellar spectral lines.

  Meanwhile, the sixty-inch reflector was readied in George Ritchey’s workshop in Pasadena, then hauled to the summit by mule train, along with 150 tons of construction and mounting materials. On December 20, 1908, four years after being funded, the sixty-inch took its first photograph. Like its groundbreaking antecedents by Henry Draper, Andrew Common, and Isaac Roberts, this latest exposure of the Orion Nebula immediately raised the measure of excellence in deep-space imaging. The instrument’s unprecedented light-gathering capacity permitted photographic and spectroscopic studies of the brighter spiral nebulae; the presence of novae—eruptive stars—in these systems plus the Andromeda Nebula’s Sun-like spectrum convinced Hale that spirals are remote stellar aggregations like the Milky Way. And as utilized by a young Harlow Shapley, Harvard Observatory’s future director, to assess the spatial distribution of globular star clusters, the sixty-inch helped ascertain the size of our galaxy and Earth’s location within it.

  Still in operation, the sixty-inch reflector is a masterpiece of engineering, featuring innovations that came to define research telescopes in its wake. For superior stability, the one-ton mirror nestles close to the instrument’s stubby, cast-iron support arms. The accumulated weight of glass and metal—altogether some twenty-two tons—floats in a trough of mercury. The driving gear alone spans ten feet, its periphery notched with 1,080 teeth. The telescope’s most radical design element at the time was not its gaping aperture, but its multifaceted utility: one instrument to serve a variety of research needs, from low-magnification, wide-field imaging to high-magnification, high-dispersion spectroscopy. The various optical paths are enabled through a set of exchangeable secondary mirrors, each configuration optimized for the particular sort of photographic or spectroscopic work being conducted. Gathered photons can be deflected out the side of the tube near the top, into lightweight cameras or spectrographs; or they can emerge near the bottom, which is better suited to bulkier apparatus. For ultrahigh-dispersion spectral work, photons can even be directed through the mounting’s hollow polar axis into an auxiliary, temperature-controlled chamber, housing a large, fixed spectrograph.

  Mount Wilson Observatory’s sixty-inch reflector fitted with a spectrograph, circa 1910.

  With the sixty-inch, no longer was it necessary for heavy, astrophysical equipment to jut from the tail of a movable telescope tube. And no longer did astronomers have to balance atop a ladder to access the high-up Newtonian focus. The telescope’s compactness reduces the size, hence, the cost of the observatory structure. Yet its multireflection optical path confers effective focal lengths up to 150 feet.

  With the various telescopes up and running, and his family ensconced below, George Hale spent much of his time in the rough, granite splendor of the Monastery. Life atop Mount Wilson alternated between the exhilarating and the mundane. Hale worked his willing staff year-round in unheated observatories; during the coldest nights, fingers and toes grew numb and lashes froze to the eyepiece. Midnight lunch consisted of hardtack and hot chocolate. Women, liquor, and coffee were forbidden. Mountain lions roamed the peak. Yet to Hale and his single-minded constituency, Mount Wilson was heaven.

  Mount Wilson Observatory staff pictured in front of the Monastery in 1906. George Ellery Hale, photographic assistant Ferdinand Ellerman, Walter S. Adams, and Edward Emerson Barnard are seated, respectively, third, fifth, sixth, and seventh from the left.

  When supplies ran low, Hale hiked down the old trail, bicycled into town, then hiked back up. (When off-mountain, he sped around on a three-wheeled Indian motorcycle, trading it in for a car after a collision with a trolley.) Hale viewed his resident colleagues as a scientific elite. Dinner in the Monastery was jacket-and-tie formal. Personalized napkin rings were laid around the table in rank order, with that evening’s large-telescope observer always seated at the table’s head. After dinner, Hale led discussions about astronomy or recited poetry. There was, according to staff astronomer Harold Babcock, “a sense of great events in the making.”

  The formative years at Mount Wilson were not without emotional challenge to George Hale and his family. In supporting her husband’s scientific efforts, Evelina Hale bore the brunt of the household responsibilities and the raising of their children. In 1906, entirely spent, she checked herself into a sanitarium for a rest cure. Hale was similarly seized by a complex array of maladies his physician summed up as “brain exhaustion.” Insomnia, headaches, and agitation were his constant companions; an innate melancholy turned into bouts of depression. Despite his active social and professional engagement, he feared he would sink into the reclusive habits of his mother and wind up a room-confined invalid. The doctor’s proposed cure was as distressing as the illness: cut back on work, adopt a balanced life. Discontented with his much-lauded accomplishments and his part-time fatherhood, Hale proved unable to rein in the full-gallop pace forced by his own outsized aspirations. His symptoms only worsened when he embarked—for a third time—on a quest to build the largest telescope in the world.

  During the summer of 1906, with Evelina confined to the sanitarium and the sixty-inch reflector still two years shy of completion, Hale spent a weekend at the estate of Los Angeles businessman John D. Hooker. After dinner, talk turned to astronomy. Hale could not help but notice Hooker’s keen interest in the subject. Sensing an opportunity, he brought up the construction of the record-setting sixty-inch telescope, then launched into a recitation about what might be accom
plished with an even larger reflector of, say, eighty-four inches. Before the week was out, Hooker offered $45,000 to cast the new glass disk and shape it into an astronomical mirror. But he insisted on a diameter of one hundred inches, worried that anything smaller might be surpassed within a few years. Hooker further stressed that the additional cost of designing, mounting, and housing the instrument was Hale’s problem. (That sum, $600,000, was eventually to be granted by the Carnegie Institution.)

  By the autumn of 1906, George Hale found himself with a half-finished sixty-inch reflector and a four-and-a-half-ton, one-hundred-inch glass lozenge on order from France; a pair of mammoth, untested telescope mounts, the latter a design concept utterly dependent on the anticipated success of the former; an institutional budget, vast by contemporary standards, yet too paltry to realize his grand schemes; a world-weary wife and a boy and a girl grown accustomed to his all-too-frequent good-byes; and, in the face of all these obstacles, an irrepressible will to push farther and fainter into the cosmos and bring the denizens of those unexplored realms under the purview of the human mind.

  The one-hundred-inch disk completed its overseas and overland journey from the Saint-Gobain foundry in France to Pasadena on December 7, 1908, the same day the sixty-inch mirror was lowered into its mountaintop cradle. Peeling back the protective coverings, Hale and Ritchey were horrified to find that the gargantuan glass was flawed. Three melts had been required to fill the capacious mold, and this had left a bubble-strewn layer with each successive pour. How such a tripartite structure might react to changes in temperature or spatial orientation was anyone’s guess. At Hale’s insistence, a second disk was poured at Saint-Gobain, but this one cracked during cooling. In yet a third attempt, the bubbles appeared again.

  By 1910, against Ritchey’s stiff opposition, Hale decided to proceed with the disk at hand. As best he could determine, the worrisome bubbles would not pock the mirror’s surface after it was scoured to its proper one-and-a-quarter-inch depth. As to the disk’s structural integrity—with no viable alternative, it was a risk Hale was willing to take. Five years of troublesome grinding, polishing, and testing ensued. Ritchey grew combative, insisting to everyone who would listen—including John D. Hooker, the project’s funder—that the massive effort would end in disaster. Hale was forced to ban Ritchey from the workspace and hire a replacement. During this period, Hale’s mental state deteriorated. “Congestion of my head,” he wrote a colleague, “is caused chiefly by worry, excitement, responsibility, discussion of any scientific subject, attendance at scientific meetings, lecturing . . . and continued mental work.”

  In January 1911, Andrew Carnegie injected another ten million dollars into his institution, expressing among his wishes that the one-hundred-inch telescope be completed. To Hale, the news was at once affirming and anxiety provoking. In this most vulnerable period of his life, he had staked both his reputation and his self-worth on a high-risk, technological gamble. Evelina grew despondent over her husband’s behavior, confiding to a sympathetic acquaintance: “He immediately began to make plans for years ahead and so worked himself up to almost the breaking point. I wished Carnegie could keep his millions to himself.” Barely six months after Carnegie’s endowment, Hale admitted himself to a sanitarium, the first of four eventual breakdowns. In the years-long aftermath, as his telescope crept toward completion, Hale strayed in and out of his self-described “neurasthenic quagmire.”

  Mount Wilson Observatory’s one-hundred-inch reflector telescope.

  The final bolt was tightened on the one-hundred-inch reflector in the autumn of 1917. The assembled behemoth weighed a hundred tons and sat on a house-sized pier of reinforced concrete. Within the pier were a mirror-maintenance shop and photographic darkroom, as well as the instrument’s star-tracking clockwork, which impelled a seventeen-foot drive wheel. The open-sided tube pivots within a rectangular steel cradle whose ends rotate almost friction-free upon mercury bearings. Despite the mirror’s extensive—and favorable—laboratory testing, Ritchey’s dire predictions of disaster hung in the air. Ultimate judgment rested on a direct view of the cosmos. Hale had to see with his own eyes whether his years of effort had paid off.

  On November 2, 1917, George Hale, Walter Adams, George Ritchey, and visiting English poet Alfred Noyes gathered for the Hooker telescope’s “first light.” Also present was a phalanx of laborers—machinists, carpenters, electricians—who had come to witness the birth of their monumental creation. After nightfall, an array of electric motors slewed the instrument eastward toward Jupiter. As the planet’s light beamed out of the eyepiece, Hale’s face must have betrayed his anguish. In place of the majestic Jovian globe appeared a kaleidoscopic mish-mash of six overlapping images that swelled across the field of view. The cause was unmistakable: the mirror was warped into a half-dozen facets, each generating its own off-kilter likeness of the planet.

  Hale suggested hopefully that the mirror might have expanded from the Sun’s heat when workmen opened the dome earlier that day; more cooling-off time might bring it back to shape. The alternative was almost too awful to contemplate: the mirror might be warping under its own weight. There was scant improvement over the next several hours, when the men adjourned to the Monastery. Around 3:00 a.m., Hale and Adams reconvened under the dome. This time, the telescope was directed at a bright star. Hale peered into the eyepiece, then shouted with joy at the prospect: a single, razor-sharp image. The mirror had equilibrated with the cool night air, its delicate arc restored. Glimpses of the Moon and Saturn clinched the case. Hale’s present nightmare was over, his dream at last ready to unfold.

  Mount Wilson’s new reflector had nearly three times the light-collecting area of the sixty-inch, and from its mile-high vantage point, was capable of probing depths of space beyond the reach of any other instrument in the world. No surprise that the attention of astronomers was turned to Mount Wilson as its great glass eye probed the heavens. Hale built the instrument, not for his own use, but for deep-sky specialists of the current and coming generations. At his insistence, the design pressed the technological limits of the era, and expressed his confidence that optical and engineering obstacles would be surmounted as they arose. The one-hundred-inch reflector was conceived as a telescope of the future as much as of the present.

  So elastic was the new instrument’s capabilities that Nobel-Prize-winning physicist Albert Michelson and astronomer Francis Pease realized that they could use it to measure the angular diameter of stars outside the solar system. To secure their results, the scientists bolted a twenty-foot-long optical device called an interferometer across the upper end of the telescope’s tube. In 1920, Michelson and Pease measured the angular width of Betelgeuse, in Orion, long suspected of being a giant star. Given an estimate of the star’s distance, they transformed the angular diameter into a physical span, confirming that Betelgeuse is indeed gargantuan compared to the Sun. The measurement created a sensation in the scientific community: an explicit example of the power of astrophysical observation. (Michelson relied on Pease for the astronomical component of the work. Once asked to identify a particular bright star in the sky—none other than Betelgeuse itself!—Michelson replied, “How the devil should I know?”)

  Finding himself unable to sustain his multitude of responsibilities, Hale resigned as director of Mount Wilson Observatory in 1922. He spent much of the subsequent time traveling, reading, and writing for the general public. Now and then, his interior eye ventured into the blackness beyond the reach of the Hooker reflector and conjured an instrument to overleap that frontier. He and his colleagues speculated about telescopes as large as three hundred inches. “Starlight is falling on every square mile of the earth’s surface,” Hale lamented in Harper’s Magazine in April 1928, “and the best we can do at present is to gather up and concentrate the rays that strike an area one hundred inches in diameter.” Readers learned that development of a much bigger reflector was feasible—if only sufficient money could be found.

  On
a whim, Hale sent a copy of his article to the Education Board at the Rockefeller Foundation. Their intense interest in the idea took him by surprise. He wrote to Lick Observatory’s Robert G. Aitken, “An article of mine on large telescopes, shot like an arrow into the blue, seems to have hit a 200" reflector.” By year’s end, Hale had negotiated a joint appropriation of six-million dollars from the Rockefeller Foundation, Carnegie Institution, and California Institute of Technology for construction of the giant instrument. Completed in 1947, nine years after Hale’s death, and named in his honor, the two-hundred-inch reflector on Palomar Mountain would mark the fourth time George Hale had fostered the largest telescope in the world. In a draft introduction to his book, Ten Years’ Work of a Mountain Observatory, Hale characterizes a scientist’s path as “steep and beset with difficulties, but it leads to heights which continually unfold new prospects of ever increasing charm.”

  George Ellery Hale at his desk in the Monastery at Mount Wilson Observatory around 1905.

  For the better part of a century, astrophysical pioneers had promoted a vision of cosmic study distinctly different from that of their traditional counterparts. The astronomical enterprise they espoused exchanged census-oriented methodologies for techniques founded on the collection and analysis of light. Thus, stars became more than mere markers of position and motion, but active, evolving engines of physics—each a full-blown sun, only diminished to a pinpoint by the vastness of space. And nebulae, those mysterious smudges of luminance in the eyepiece, acquired their true identity as free-floating reservoirs of cosmic chemicals. Further clues to the physical properties of these far-flung populations were sought in celestial photons that drizzle over Earth. Forward-thinking observers like George Ellery Hale pushed for a new generation of instruments to intercept the faintest emissions, even though the key to decode them did not yet exist.