Starlight Detectives

by Alan Hirshfeld

  Edward S. Holden.

  Hussey informed Holden that he would use the Crossley telescope—after its mount was replaced. Holden refused. The standoff escalated to the point that Hussey stopped speaking to Holden, communicating instead through terse, handwritten notes (as had Barnard before he left). The staff broke into factions, the majority allied with Hussey. Eventually the board of directors stepped in to mediate. The San Francisco Chronicle got wind of the impasse and ran a series of devastating articles, telling readers that a “peace commission is already on its way to the scene of the hostilities.” When Holden had the Crossley’s dome roped to the telescope mount to prevent it from blowing away in a storm, the Chronicle opined that the board of directors “rather wish the accident had occurred,” taking the telescope with it.

  News of the controversy raced across the Atlantic, where the editors of The Observatory magazine declared, “[T]here is civil war on top of Mount Hamilton.” They highlighted the affront to Andrew Common’s achievement and to Edward Crossley’s generosity, then added in a metaphorical stretch, “Why should a Derby-winner end his days between the shafts of a four-wheeler?”

  The board of directors eventually sided with Holden, but to no real effect. Hussey made a desultory attempt to observe with the Crossley telescope, but only visually, ignoring its photographic potential. On January 1, 1898, after staff relations worsened and with the threat of a lawsuit against him, Holden resigned his post. Hussey stayed on at Lick until 1905, when he left to oversee the expansion of the observatory at the University of Michigan. His first purchase: a three-foot reflector telescope.

  Holden’s successor, James Keeler, was no stranger to Mount Hamilton when he took up the Lick directorship in June 1898. He had been a staff astronomer there from 1886 until 1891, setting up Lick’s regional time service, witnessing construction of the thirty-six-inch refractor, and fabricating a spectroscope for its use. The lowlands-bred Keeler would have reveled in his lofty vantage point on the Milky Way, which rises vertically from the horizon every August. All around the close-packed hive of high technology was a “sparsely wooded mountain land where are met only deer, skunks, squirrels, roaming astronomers, coyotes, an occasional mountain lion, a few horses, and, in summer time, rattle snakes, while the big, black buzzards sail high in the air on the outlook for a little food.”

  With a dual degree in physics and German from Johns Hopkins, graduate education in Heidelberg and Berlin, and a string of noteworthy publications from his tenure as director of Allegheny Observatory, Keeler was hailed as one of America’s premier astrophysicists, equally adept in the theoretical and observational realms. He was the rare scientific administrator who engendered respect through his own professional accomplishments, and spurred his charges through a combination of modesty and charming inquisitiveness. As one colleague put it, “Keeler doesn’t claim to know everything.”

  Keeler’s top priority was to settle the Crossley debacle, which had escalated beyond all reasonable proportion. The Lick Observatory was portrayed in the popular press as an unproductive aerie of bickering hacks, so self-absorbed, claimed one newspaper, that they would miss a comet if it flew right over their heads. And the reputation of Edward Crossley, who sat on the Lick’s board of directors, continued to be tarnished by the all-too-public squabbles over his eponymous telescope. Within a month of his arrival, Keeler defused the situation: he reassigned William Hussey to more desirable duties and took charge of the problematic reflector himself. An immediate test of the mirror’s figure revealed it to be nearly flawless. Under the limpid skies of Mount Hamilton, the telescope might yet fulfill its promise, if only unfettered by its scandalous mount. The Crossley, Keeler suspected, was a thoroughbred trapped in the body of a nag.

  In 1900, Keeler published a twenty-five-page article in the Astrophysical Journal detailing a host of incremental refurbishments, parts swaps, and procedural tweaks applied to the Crossley telescope. The long tally of labor leaves no doubt that Keeler had stripped the ungainly beast down to its bones and observed every component in action—or inaction. A new, more powerful clock drive advanced the massive tube without its predecessor’s frustrating palpitations. Whatever irregularities remained were overcome by the more or less constant intervention of an assistant. Keeler’s article left the impression of an almost comic duo: the immobile astronomer, peering into the camera’s guiding eyepiece; and his frenetic assistant, clambering over the superstructure to apply the requisite adjustments.

  James E. Keeler.

  Keeler’s appraisal of the telescope’s checkered history is diplomatic in the extreme. In a footnote, he neatly absolves everyone of responsibility in the Crossley affair, and pays a tangential compliment to Andrew Common for having accomplished what he did: “The difficulties here referred to, about which a good deal has been written, seem to have had their origin in the fact that it was impossible, at the time of the preliminary trials, to provide the observer with an assistant, while the Crossley reflector is practically unmanageable by a single person.”

  Once its mechanical demons were exorcised (or at least subdued), Keeler confirmed his suspicion that, as a photographic tool, the Crossley telescope was superior to Lick’s great refractor. Not only did it have a wider field of view—one degree across—its compact optical path more effectively concentrated light onto its 3¼" × 4¼" plates: a three-hour exposure of the Orion Nebula with the refractor showed less detail than a ten-minute exposure through the Crossley. Keeler also noticed a photographic boost from the mirror’s silvered surface, which, unlike a glass lens, absorbs few of the violet rays that activate the plate’s chemical emulsion. He writes, “On one of the fine nights . . . when the Milky Way shines with astonishing splendor and the whole heavens look phosphorescent, the photographic activity of the reflector is remarkably increased.”

  In its mountaintop setting, Andrew Common’s twenty-year-old telescope was reborn with a vigor that would have delighted its creator. The central star of the Ring Nebula in Lyra, a challenge to photograph at the time, rendered a distinct image in just one minute. Stars of magnitude seventeen, beyond the light grasp of most 1890s-era telescopes, appeared on the plate in only ten minutes. A thirty-second exposure—practically a snapshot in the astronomical sense—was sufficient to capture the subtle nebulosity enveloping the Pleiades. Nearly fifty-four-hundred stars speckled a two-hour plate of the globular star cluster Messier 13 in Hercules.

  Keeler coaxed the Crossley to successively longer exposures, culminating in a series of celestial portraits, each four hours in duration. The nominal targets were a gallery of well-known objects, yet Keeler’s eye was drawn to the large number of lesser wisps surrounding them. Like the spray of stars that had unexpectedly dotted David Gill’s photographs of the comet of 1882, each of the Crossley plates displayed a host of never-before-seen nebulae: typically eight to ten, with one exposure showing thirty-one. Keeler estimated that the nebular population within range of the Crossley over the entire sky surpassed 120,000, some ten times the number previously cataloged. And, if the new images were any indication, the vast majority of these presumed deep-space denizens were spiral in form.

  Lick Observatory’s thirty-six-inch Crossley reflector on its original mounting, 1898.

  The release of Keeler’s photographs galvanized the astronomical community. The spiral nebulae, a celestial species once considered rare, turned out to be among the most populous breeds in the astronomical zoo. Their explication took on an urgency, spurred by their sheer weight of numbers. The dark and seemingly empty fields between the stars now sparkled like untapped veins of scientific opportunity. In these mysterious whorls of light lay, in Thoreau’s phrase, “winged seeds of truth.” But of what truth? If a reflector of such humble origin and scale uncovered hundreds of thousands of spiral nebulae, how many more might be revealed by a generation of larger, more sophisticated instruments? Might the universe be characterized as much by the ubiquity of its spiral nebulae as by that of its stars? Fundamentall
y, does our cosmos consist of a single island of luminous matter amid the void or is it a vast ocean of space containing multitudes of galactic systems like our own?

  Having proven the Crossley’s worth as a surveyor of spiral nebulae, Keeler next made plans to equip it with a spectrograph. The telescope’s fast optics and mountaintop site would confer a distinct advantage over its sea-level rivals in recording the feeble trace of a nebular spectrum. Telltale features in the spectrum, Keeler hoped, might disclose something of the spirals’ physical nature, specifically, whether they consist of stars or diffuse gas. The spectrograph was completed on July 30, 1900, but Keeler never got to use it. He descended the mountain that day to seek medical treatment for a longstanding heart ailment. Eleven days later he was dead. James Keeler’s final journal publication bore the title “The Crossley Reflector of the Lick Observatory”—a fitting tribute to the indomitable bond between an astronomer and his telescope.

  From its crude beginnings in the 1840s, celestial photography evolved over a span of six decades into an essential research tool in astronomy. Its earliest practitioners proceeded on the dubious, yet irresistible, prospect that their technological prowess could surmount the manifold hurdles of low-light imaging. Their grainy frames were remarkable for the time, each one prized as a chemical reliquary of a star’s luminous essence. The initial decades were the province of amateur enthusiasts, whose progress stemmed from equal measures of ingenuity, perseverance, and cooperation. The heavenly scenes grew richer—first approaching, then challenging, and finally surpassing the capability of the human eye at the telescope.

  With the application of the dry plate in the 1880s, what had been a noisome, exasperating art became a predictable, mainstream technology that would eventually recast the telescope as an adjunct of the camera. One-time Lick Observatory director Edward Holden noted that the camera “does not tire, as the eye does, and refuse to pay attention for more than a small fraction of a second, but it will faithfully record every ray of light that falls upon it even for hours and finally it will produce its automatic register . . . [that] can be measured, if necessary, again and again. The permanence of the records is of the greatest importance, and so far as we know it is complete . . . We can hand down to our successors a picture of the sky, locked in a box.”

  Mindful of the accomplishments of their venturesome colleagues, professional astronomers increasingly embraced celestial photography as an essential observational astronomical tool. Together, Isaac Roberts’s deep-sky portraits, Edward Emerson Barnard’s panoramic views of the Milky Way, and James Keeler’s multitude of spiral nebulae brought a new clarity to the architecture and demography of the universe. As the twentieth century unfolded, photography’s expanding reach spurred development of a new field of cosmic exploration: extragalactic astronomy.

  Yet pictures alone were insufficient to answer the sorts of questions posed by practitioners of the “New Astronomy.” These academically trained scientists sought to apply the laws of physics to the inner workings of stars and nebulae. They stood ready to pivot on new methods or cross disciplinary boundaries, if it enabled them to decode the cosmic light swept up by their telescopes. As crisp as it might appear, the image of a heavenly body betrays the fundamental limitation of a picture: No matter how much it magnifies a distant world, it reveals little to nothing about the chemical composition or physical state of a planet’s soil, a comet’s tail, or a star’s atmosphere. The indiscriminate cluttering of light upon the photographic plate—the visual equivalent of simultaneously tuning in every radio station on the dial—renders only the form of a celestial object.

  While celestial photographers labored to improve chemical emulsions and telescope drives, their astrophysical counterparts explored a promising, often confounding, realm of analysis: dispersing starlight into its constituent colors before it strikes the plate. Astronomers suspected that this faint array of colored bands—the star’s spectrum—might be used as a laboratory-like probe into the star’s elemental makeup and physical properties. Decades of research proved that to be the case. Modern astronomy owes its refinement not only to the introduction of the camera, but to the concurrent development of an equally marvelous instrument: the spectrograph.

  Part II

  SEEING THE LIGHT

  The physicist and the chemist have brought before us a means of analysis that . . . if we were to go to the sun, and to bring away some portions of it and analyze them in our laboratories, we could not examine them more accurately.

  —Warren De La Rue, “Proceedings of the Chemical Society,” June 20, 1861

  Chapter 13

  THE ODD COUPLE

  The most important discovery made by Bunsen during the short duration of his residence in Breslau was the discovery of Kirchhoff.

  —Henry Enfield Roscoe, Bunsen Memorial Lecture, Chemical Society, London, 1900

  ROBERT WILHELM BUNSEN WAS FEARLESS in the laboratory, even after the chemical explosion in 1836 that shattered his face mask and cost him the sight in his right eye. Bunsen routinely investigated toxic substances like the arsenic compound whose smell, he reports, “produces instantaneous tingling of the hands and feet, and even giddiness and insensibility . . . [while] the tongue becomes covered with a black coating.” The arsenic study nearly killed him. On at least one occasion, he had to be roused from unconsciousness brought on by fumes from his noxious brews. So calloused were his hands from chemical exposure that he declined protective aids. Bunsen’s protégé, English chemist Henry Roscoe, remarked that his mentor “had a very salamanderlike power of handling hot glass tubes, and often at the blowpipe have I smelt burnt Bunsen, and seen his fingers smoke!”

  Having established his bona fides at Göttingen, Cassel, Marburg, and Breslau, Robert Bunsen was practically a legend when he was brought in to lead the chemistry institute at the University of Heidelberg in 1852. At twenty-three, Bunsen had developed an antidote to arsenic poisoning by chemically rendering the toxin insoluble in bodily fluids. His exhaustive study of organic compounds known as cacodyls had placed him in the top rank of experimentalists by the mid-1840s. He had reshaped the economics of the iron-making industry in both his native Germany and in England by improving the efficiency of blast furnaces; explored the geochemistry of Icelandic volcanoes and geysers, descending into the vents to take temperatures; and created a low-cost carbon-zinc battery, as well as a forerunner of the carbon arc lamp. It was at Heidelberg that Bunsen would fashion the hot-yet-colorless laboratory burner that bears his name—and where he would help transform the astronomical telescope from a mere eye on the heavens into a cosmo–chemical probe.

  The depth and breadth of Bunsen’s published works evinced a relentlessness of purpose perhaps unique in the chemical world. In 1844, Swedish chemist Jöns Jacob Berzelius, the foremost experimentalist of his time, urged a colleague to pursue an investigation “with the true perseverance of a Bunsen.” By midcareer, the Heidelberg chemist had risen to cultural icon. A character in Ivan Turgenev’s 1862 novel Fathers and Sons confesses how she longs to travel, not only to Paris, but to Heidelberg. “Why Heidelberg?” asks her puzzled companion, to which she replies, “Good heavens, Bunsen’s there!”

  During construction of Heidelberg’s new state-funded chemistry building—which he negotiated into his hiring package, along with the university’s second highest salary—Bunsen set up in an abandoned monastery. The age-old house of God was repurposed with the secular implements, rituals, and agents of modern science. The former refectory became the main laboratory, while the chapel served as both lecture hall and storeroom. To accommodate the rush of students eager to work with Germany’s star chemist, the cloisters were subdivided into experimental alcoves. All of the specialized glassware was manufactured on site, much of it hand-blown by Bunsen himself. Until the installation of gas and running water, the researchers heated their concoctions with spirit lamps and charcoal fires and worked the pump handle in the courtyard. “Beneath the stone floor at our feet slept th
e dead monks,” was Henry Roscoe’s dispassionate take on the abbey-turned-laboratory, “and on their tombstones we threw our waste precipitates.”

  Bunsen, a lifelong bachelor, was married to his occupation. He rose before dawn to pen scientific papers, delegated little work to assistants, and dedicated considerable vacation time to industrial or geochemical field studies. Even in repose, Bunsen was on the job: having drifted off during a colleague’s lecture, he jerked awake and whispered to Henry Roscoe with relief, “I thought I had dropped a test-tube full of rubidium onto the floor!”

  A broad-shouldered six-footer, “Papa” Bunsen, as he was affectionately known to his students, was the amiable lord of the laboratory, ambling from table to table, admonishing trainees for their sloppy technique or alerting them to potential dangers. On occasion, experimenters arrived in the morning to find their project several steps advanced from where they had left it the night before. Bunsen radiated enthusiasm about even seemingly mundane aspects of scientific exploration. “It was quite in keeping with his nature,” recalled a former student, “that others should partake of the infinite pleasure he had experienced.”