Starlight Detectives

by Alan Hirshfeld

  Spindly and shy, William Bond possessed a quick mind, skillful hands, and a horologist’s sensitivity to the rhythms of nature. To his friends and his elder brother Thomas, he was the clever craftsman, a reliable producer of animal snares, sports toys, and makeshift “scientific” apparatus. An unlikely clockwork that he fashioned at age ten from wood scraps had kept tolerable time. A handmade astronomical quadrant, of ebony and boxwood, evinced “the neatness, patience, and accuracy of a practiced artist.” Despite these precocious glimmers of talent, William Bond felt trapped by his family’s near-ruinous finances, having confided to his mother, Hannah Cranch, that he was “in despair of ever being able to accomplish anything.”

  Today, William Bond stood in the quickening daylight, having witnessed the Great Eclipse from a housetop on Summer Street. The precious minutes of totality had allowed him two simultaneous, yet divergent, views of the event: the panorama of Earth, sea, and sky afforded by the unaided eye; and magnified glimpses of the solar–lunar disk through a family friend’s telescope. It’s not known which of these prospects left the stronger impression on Bond—the epic sweep of nature’s stage, offered equally to all, or his own private telescopic vision of the Moon’s mountainous limb silhouetted against the solar corona.

  Bond had been warned, of course, not to stare at the Sun, even in its constricted state. His pupil would have widened in the dimness of totality, leaving him defenseless against the Sun’s inevitable return. Yet he had been powerless to tear his eyes away from the singular sight. Thankfully, the worrisome dazzle of light and shade that now presented itself everywhere he looked would resolve itself over the coming weeks. On a deeper level, Bond’s vision was absolutely clear: no contrivance he might ever generate at his artisan’s workbench would be sufficient to satisfy his newfound desire to unmask the mysterious clockwork of the heavens. Science was the only route to this end. Every day forward would be devoted to the pursuit of a goal inaccessible, in the main, to someone without a formal education: “Then and there,” Bond’s granddaughter Elizabeth writes in her memoir, “he vowed to himself to become an astronomer.”

  The so-called classical astronomy of William Bond’s era was very different from the astrophysical science practiced today. Essential analytic adjuncts to cosmic research—photography and spectroscopy; the physics of atoms, energy, and space; electronic computers—lay far in the future. Telescopes were abundant, but with few exceptions, they were small, crude, and in less-than-capable hands. Examination of lunar and planetary surfaces was largely left to amateur astronomers. Comets, stars, and nebulae were notional rather than physical bodies, both their origin and their action opaque. The measured limits of our Milky Way galaxy were so ragged as to obscure its true extent and form. Nobody perceived that there were other galaxies, much less that these starry islands exist in virtually countless numbers within an expanding universe of finite age.

  Lacking the instrumental and theoretical bases to do more, much of early nineteenth-century astronomy was restricted to the determination of positions and motions of heavenly objects. These results, in turn, were applied to tasks such as terrestrial navigation, forecasting eclipses and planetary conjunctions, or predicting the periodical return of comets. That Isaac Newton’s mathematical law of gravitation found uniform corroboration within the celestial realm was a marvel of the age. Indeed, Newtonian analysis was a quantitative engine fueled by astronomical data. German astronomer Friedrich Wilhelm Bessel, who in 1838 measured the first distance to a star, asserted that the sole mission of the telescopic astronomer is to obtain the data “by which Earth-bound observers can compute the movements of the heavenly bodies. Everything else that one might learn about these bodies—the appearance and constitution of their surfaces, for example—may be worthy of attention, but it is of no real concern to Astronomy.”

  In transforming the Royal Greenwich Observatory into a veritable factory of positional astronomy during the mid-nineteenth century, England’s Astronomer Royal George Biddell Airy allied with Bessel’s narrow view of cosmic studies. The observatory’s purpose, Airy asserted, is not for “watching the appearances of spots in the sun or the mountains in the moon, with which the dilettante astronomer is so much charmed. . . . [I]t is to the regular observation of the sun, moon, planets, and stars . . . when they pass the meridian, at whatever time of day or night that may happen, and in no other position.”

  George Biddell Airy, England’s seventh Astronomer Royal.

  It was in the 1700s that astronomy and geography were wedded in the name of governmental interests and overseas commerce. Boundary disputes were common between political entities. Many colonial-era land grants in America were based on lines of latitude or longitude, easy to sketch on a map, notoriously difficult to fix in the field. The decades-long row between William Penn and Lord Baltimore over the extent of their respective colonies was not settled until the 1760s when Charles Mason and Jeremiah Dixon applied astronomical methods to delineate the Pennsylvania–Maryland border. Even a prominent scholar like Friedrich Bessel could be rousted out of his observatory to measure the length of a degree of latitude in Prussia.

  Astronomers routinely accepted such earthbound intrusions on their research time, if not for patriotic reasons, then for a simple truth: a surveyor could construct only a relative map of a nation; an astronomer could situate its borders absolutely within the framework of the world. By William Bond’s time, fully half of all astronomers were involved in terrestrial position measurement, and more geography-related papers appeared in the astronomical literature than ones on purely celestial topics.

  Positional astronomy was likewise applied to transoceanic navigation. “The prosperity of commerce,” wrote American astronomer Elias Loomis in 1856, “depends entirely upon . . . the accuracy with which a ship’s place can be determined from day to day. Had it not been for the labors of modern astronomers in their observatories, vessels would still, as in ancient times, creep timidly along the coast, afraid to venture out of sight of land; or if they were compelled to venture into the open ocean, they would be exposed to imminent danger in approaching land, not knowing how far distant the port might be.”

  Sailors’ lives and ships’ cargoes depended on the accurate delineation of coastlines and shoals. The most effective geo-positioning system for a sailing vessel was astronomical, involving shipboard sightings of the Sun, Moon, or even the configurations of Jupiter’s satellites. Given Earth’s diurnal rotation, keeping precise track of the passage of time was critical to celestial marine navigation. Monetary awards were offered for improvements in the determination of longitude at sea, as well as for mathematical analyses of lunar motion. Englishman John Harrison’s prize-seeking marine chronometer of 1761 deviated a mere five seconds during a transatlantic voyage of 161 days.

  One of the hallmarks of classical astronomy was its insistence on exactitude, starting with the precise establishment of the observer’s latitude and longitude. The determination of one’s latitude is straightforward, from a measurement of the altitude of the celestial pole (approximated in Earth’s Northern Hemisphere by the star Polaris). The determination of longitude is more difficult, given Earth’s rotation. In William Bond’s day, longitude was reckoned astronomically by timing the meridian passages of prominent stars, the celestial analog of surveyors’ reference stones.

  In practice, the astronomer erects a telescope whose axial movement is constrained to the meridian: the north–south arc in the sky that passes through the zenith, directly overhead. Because stars traverse the night sky from east to west (a reflection of Earth’s west-to-east rotation), the telescope can be swung around its free axis to intercept each star as it crosses, or transits, the meridian. A chronometer gauges the precise time of transit, whereas a degree-scale on the telescope’s axis indicates the star’s altitude above the horizon. Mathematical analysis of transit times and altitudes for a set of reference stars yields the observer’s geographic coordinates. The local time difference between the oc
currence of a celestial event at, say, Greenwich, England, versus Boston reveals the interval in longitude between these two points. That knowledge, in turn, permits coordination of astronomical measurements from observatories around the world. The more precise the observer’s transit measurements, the more precise the resultant longitude.

  Transit telescope at the observatory in Besançon, France.

  The quest for precision in measurement and analysis had a profound effect on the conduct of astronomy in the 1800s. To its ranks came meticulous, mathematically minded practitioners, eager to embrace an arduous multiplicity of tasks. Their passion extended beyond the study of celestial objects to the identification and quantification of errors in telescopes, chronometers, even the observers themselves. Every telescope, Friedrich Bessel told an audience in 1840, harbors microscopic defects that are revealed only through detailed, systematic observations of the heavens. In Bessel’s view, a telescope has to be built twice, “once in the workshop of the artisan, from brass and steel, and again by the astronomer, on paper, through the application of necessary corrections obtained in the course of his investigations.”

  To ferret out and computationally nullify an instrument’s shortcomings, the astronomer turns interrogator: Is the telescope’s lens at a precise right angle to the light passing through it? Does the lens sag when the telescope is tipped toward a different direction? Are the mount’s rotation axes exactly perpendicular? Does the telescope tube warp under the pull of gravity? Is the instrument level to the ground and aligned north-to-south? Are vibrations of the astronomer’s footsteps transmitted to the instrument? Are the markings on the brass coordinate circles equally spaced? Do the circles themselves contract in the cool night air?

  Celestial measurement is further muddled by noninstrumental factors that conspire to shift the apparent position of a star in the sky. Earth itself is an imperfect platform from which to observe the heavens. It hurtles around the Sun, spins, and precesses like a top. Its atmosphere swells and agitates the image of a star, whose incoming rays might deflect up to half a degree as they traverse the layers of air. These effects, like instrumental and personal flaws, could be offset by mathematical adjustment of the raw measurements. There were no shortcuts in this line of rigorous observation, nor any promise of fame through discovery, only the chance to make an incremental contribution to the advancement of science.

  Fervent as William Bond’s cosmic aspirations were, an academic pathway into the profession was nonexistent in early 1800s America. The shuttering of David Rittenhouse’s Philadelphia-based observatory upon his death in 1796 left not a single permanent observing facility anywhere on the continent. One astronomical wag defined an American observatory as “a tube with an eye at one end and a star at the other.” Attempts by private and public institutions to establish observatories in the United States withered for lack of money. Harvard College prodded wealthy patrons for a research-grade telescope four times before 1825; all of these attempts were unsuccessful. The American Philosophical Society leased space for an observatory in 1817, but failed to raise the added money to buy a telescope. Conversely, Yale purchased a five-inch refractor in 1828, but had no observatory in which to mount it. In 1830, a frustrated president of the University of North Carolina dipped into his own pocket to fund a campus observatory. Its cost: $430.29½.

  During their respective terms, Presidents James Monroe and John Quincy Adams petitioned Congress to create a national observatory. Foreshadowing the nationalistic thrust of the Apollo-era race to the Moon, Adams told legislators in 1825:

  It is with no feeling of pride that, on the comparatively small territorial surface of Europe, there are existing upward of one hundred and thirty of these light-houses of the skies; while throughout the whole American hemisphere there is not one. . . . And while scarcely a year passes over our heads without bringing some new astronomical discovery to light, which we must fain receive at second-hand from Europe, are we not cutting ourselves off from the means of returning light for light, while we have neither observatory nor observer upon our half of the globe, and the earth revolves in perpetual darkness to our unsearching eyes?

  Congress was unmoved, seeing no commercial or political value in governmental sponsorship of basic scientific research; sponsorship of such efforts was the province of states and private institutions. To underscore their opposition, legislators tacked on a proviso to the budget of the U.S. Coast Survey, a mapping project begun in 1807, specifying that “nothing in this act should be construed to authorize the construction or maintenance of a permanent astronomical observatory.”

  Facilities aside, the United States lacked a vibrant professional astronomical community: although many scientists in the early 1800s credited astronomy’s scholarly worth, as well as its practical importance, the nation’s full-time astronomers could be counted on the fingers of one hand. The Coast Survey was virtually the only source of employment for the nonacademic astronomer. Nor were there any academic training programs in astronomy beyond the general undergraduate curriculum. Absent self-instruction, the aspiring astronomer pursued advanced training through academic apprenticeship, ideally overseas. Europe was the nexus of astronomical studies, primarily Germany, Britain, and France. An 1832 report on global astronomical research by Cambridge astronomer George Biddell Airy does not mention the United States at all.

  It would not be until the mid-1830s that American educational institutions embarked on what turned into an observatory building spree. In 1836, Williams College would break ground on a stone building with a thirteen-foot revolving dome to house a pair of small telescopes. Western Reserve College in Hudson, Ohio, would simultaneously embark on its own building program for a four-inch refractor acquired in England. Within two years, Philadelphia Central High School would place a six-inch, German-made refractor atop a domed tower, and by decade’s end, West Point would feature three such towers on its grounds. The Federal Depot of Charts and Instruments, created in 1830, would expand over the following two decades into the U.S. Naval Observatory, complete with a dedicated facility, sophisticated equipment, and full-time staff. But for a young, middle-class Bostonian like William Bond, these developments lay in the future. Bond would have to chart his own route into the celestial domain.

  Chapter 2

  THE INGENIOUS MECHANIC OF DORCHESTER

  No living man . . . has done so much drudgery for science, with so slight a reward, as William C. Bond.

  —Astronomer William Mitchell, “The Astronomical Observatory of Harvard University,” 1851

  IN THE YEARS FOLLOWING THE 1806 ECLIPSE, night became William Bond’s refuge from the daytime drudgery of the clockmaker’s shop. He evidently complained to no one—save his mother—about the long hours or the relentless pressures of a business to which his father, having failed twice in the lumber trade, seemed no better suited. At his workbench, Bond patiently assembled mechanical implements of time; yet he longed for the end of day, when he could resume his study of the celestial clockwork. In tracking these cycles, he might uncover the mainsprings, escapements, and regulators that make the cosmos run true.

  The stars would have glistened brightly over William Bond’s Boston, their radiance unimpeded as they are today by city lights. Bond memorized the constellations and how they cycled through the seasons. He noted the synchronous pas de deux of the Sun and Moon, as well as the stately adagio of planets against the starry backdrop. He gauged separations between stars with a knotted string held up against the sky, as English astronomer William Herschel had done before he became famous. Now and then, a meteor would streak above his head, hell-bent on its rendezvous with oblivion.

  William Cranch Bond.

  Each of these nocturnal communes with nature began the same way, with Bond staring into a well for ten minutes. “[H]is optic nerve became so stimulated,” writes his granddaughter Elizabeth, “that he acquired almost telescopic vision and could see stars invisible to others.” The spurious claim of telescopic vision aside,
once his eyes were adapted to the dark—an essential practice among serious night-sky observers—Bond was well attuned to serendipitous events in the heavens.

  On the night of April 21, 1811, Bond noticed a faint whitish blur to the south, a few degrees above the star Sirius in the constellation Canis Major. With the night sky now as familiar to him as his own neighborhood, he knew at once that the object was out of place. It hadn’t been there any night before. A longer look brought out the indistinct, yet unmistakable, image of a luminous tail, about a degree in length, projecting from the diffuse core. Bond measured the celestial coordinates of the object. He did the same three nights later and again on several occasions in May before he surrendered to his mounting excitement. The object was moving. He had discovered a comet.

  It was only later that Bond learned that what would become known as the Great Comet of 1811 had, in fact, been discovered in Europe a month beforehand. But he was the first observer in America to see it. By autumn, the comet blazed brighter than almost any other in history, extending its tail a full twenty-five degrees. Word of Bond’s visual feat reached Professor John Farrar, mathematician and astronomer at Harvard College, and Nathaniel Bowditch, the nation’s foremost expert on celestial navigation. Impressed, the two scientists featured Bond’s comet observations in their own report to the American Academy of Arts and Sciences in September 1811, introducing him to their colleagues as an “ingenious mechanic of Dorchester, Massachusetts.” Congressman Josiah Quincy, who would go on to serve as mayor of Boston and then President of Harvard, encouraged the twenty-three-year-old to pursue his dream. One eclipse and one comet into his calling, William Bond had stepped into the inner circle of American science.