The Day We Found the Universe - Marcia Bartusiak (2009)
Chapter 2. A Rather Remarkable Number of Nebulae
Keeler traveled to the Lick Observatory along a road that was a marvel of engineering in its day. Although Mount Hamilton is less than a mile high, the journey from its base to the top is more than twenty miles in length, with the roadway sinuously zigging and zagging as it gradually ascends. There are some 360 switchbacks in all, and some were even given special names, such as “the Tunnel,” “Crocodile Jaw,” and “Oh My Point,” branded by the oft-heard refrain as people sat atop the stagecoach and looked down in horror at the point's steep drop-off. The serpentine route was installed to maintain a gentle gradient, so that stagecoach horses in the nineteenth century never needed to break their stride.
Upon reaching the top, Keeler was immediately enamored of the breathtaking scenery. “The view from the observatory peak is a very beautiful one, particularly in the spring, when the surrounding hills are covered with bright green verdure, and the eye looks down upon acres of wild flowers,” he later wrote in a pamphlet for visitors. “To the west lies the lovely Santa Clara valley, shut in from the ocean by mountains somewhat lower than the Mt. Hamilton range. Sometimes the entire valley is filled with clouds, rolling onward under a clear sky and bright sun like a river of snow… The surrounding mountain tops project out of the fog like black islands.” Often the ocean fog arrives at sunset, rolling in from the Pacific at the Golden Gate, to the north, and Monterey Bay, to the south.
Not everyone on the mountain was enthusiastic about Keeler's arrival. The observatory's superintendent, Thomas Fraser, was initially wary of the newcomer. “If he has the right ring all will be right,” said Fraser, “but if Stubern [sic] then things will go wrong and he will have to leave that is all there is to it.” It didn't take long, though, for Fraser to be won over by the exceptional skill Keeler displayed as the telescope was being prepared for operation.
Its great lenses were finally installed on New Year's Eve 1887, but due to severe weather the staff could not test the telescope out until a few days later. Often in the wintertime, storms would sweep over the mountain with winds gusting more than 60 miles per hour, which would drift the snow about the dwellings more than ten feet high. Once the staff got back to the telescope, the trial run did not go well. To their horror the astronomers discovered that Alvan Clark, the telescope maker, had misstated the instrument's required length. Much like the Hubble Space Telescope's initial mishap a century later, they couldn't get it into focus. The telescope's tube should have extended fifty-six feet, but instead was six inches too long, forcing them to get out their tools and spend valuable days cutting the tube down to size. Clark's son, a partner in the telescope firm, was there for the trial, “a terrible old blow and grumbler,” Keeler told Holden. While Clark insisted that his firm's glass was superb and the eyepieces “triumphs of art,” he declared the dome “worthless.”
With its tube shortened, the telescope was at last tried out on January 7, 1888, a cloudless night that was piercingly cold. With the dome frozen solid that evening, the handful of staff members and guests present could only passively observe the objects that happened to pass by the dome's slit, open toward the southeast. Yet, “no inconvenience was felt beyond the necessity of a little waiting,” recalled Keeler. He was pleased to find the clock running smoothly and the mounting working well. The group first observed Rigel, a blue-white double star, followed by the Orion nebula, its great streamers making it one of the most spellbinding sights through a telescope. “Here the great light-gathering power of the object glass was strikingly apparent,” Keeler noted. Then, just after midnight, Saturn came into view. Keeler reported that the planet was “beyond doubt the greatest telescopic spectacle ever beheld by man. The giant planet, with its wonderful rings, its belts, its satellites, shone with a splendor and distinctness of detail never before equaled.” Everyone in the party took a look. Afterward Keeler spent some time studying Saturn more carefully, which led to Lick Observatory's first discovery. He spied a fine, dark line in Saturn's outer ring, “a mere spider's thread,” as he described it. It was a breach (now best known for historic reasons as the Encke Gap, after an early-nineteenth-century German astronomer) that had never before been clearly seen. A superb drawing Keeler made of Saturn, based on his sketch of the planet that night, was displayed at the 1893 Chicago World's Fair.
(Mary Lea Shane Archives of the Lick Observatory, University
Library, University of California-Santa Cruz)
Six feet tall with fair wavy hair, Keeler cut a fine figure. Despite his isolated upbringing in rural Florida, he became a keen judge of human nature and was often called upon to handle personnel and scientific crises at the observatory, which he carried out with the calm discretion of an international diplomat. “He was tolerant, amused and unwilling to take sides,” said Keeler's biographer Donald Osterbrock. “He always sought to put the best construction he could on anyone's activities, to emphasize the positive, and never to criticize unless absolutely necessary. It was perhaps not the most courageous philosophy in the world, but it [took] him far.”
And as an astronomer, Keeler was outstanding, studying a range of subjects from solar eclipses to planetary features. Photography was still in its infancy, so Keeler continued to make drawings that were praised by his colleagues as marvelous reproductions. “Beautiful and accurate,” reported fellow Lick astronomer Edward E. Barnard in a notice to the Royal Astronomical Society. “… [Keeler] has a real artistic ability such as very few observers possess.” Keeler's real forte, however, was in using a spectroscope, which was a relatively recent addition to astronomy's instrumental arsenal. The scientific basis for it was established in the seventeenth century.
A young Isaac Newton, sitting in a darkened room in 1666, let a small stream of sunlight enter through a hole in his window shutter. He then passed it through a triangular prism of glass. Beholding a rainbow of colors on the wall behind him, an enchanting phenomenon observed with pieces of glass since antiquity, Newton clearly demonstrated that white light was a mixture of many hues: On one end was a band of red, followed by orange, yellow, green, and blue, until it reached a deep violet on the other end. He dubbed this multicolored display a spectrum, a word previously used to denote an apparition or phantom. By the early nineteenth century Joseph von Fraunhofer, a master Bavarian optician, cleverly combined a slit, a prism, and a small telescope—what came to be called a spectroscope—to examine the spectrum of the Sun more closely. Peering through the eyepiece, he was surprised to discern hundreds of dark lines in the spectrum, as if a series of black threads had been sewn across a rainbow. They resembled the ubiquitous bar codes now found on consumer products. But unfortunately, Fraunhofer died before he could pursue the origin of those mysterious dark slashes.
Answers arrived from the creative experiments being conducted in chemistry laboratories. Even before Fraunhofer's spectral tests, chemists had noticed that metals or salts, when heated to incandescence, emit certain colors. Salts containing sodium, for example, burn an intense yellow-orange when heated by a hot flame. When looking at the heated material through a spectroscope, the chemists saw that its spectrum was composed of discrete lines of color, resembling a picket fence with colorful posts. Whereas the solar spectrum was a continuous rainbow riddled with dark lines, these laboratory spectra were the exact opposite: thin bright lines of colorful emissions set against a dark background.
By 1859 the physicist Gustav Kirchhoff and the chemist Robert Bunsen (creator of the legendary lab burner) at last revealed the meaning behind these bright and dark lines. With the clear hot flame of Bunsen's improved instrument, free of the deceptive contamination that plagued earlier researchers, the two German colleagues were able to conclusively prove that each chemical element produces a characteristic pattern of colored lines when heated and viewed through a spectroscope. The elements weren't emitting an entire rainbow but rather just a few select colors. More consequential, the patterns were as unique and distinguishing as a fingerprint. Each element on the periodic table had its own personal set of emissions. Using their spectroscope one evening to peer at a distant fire in the port city of Mannheim, visible across the Rhine plain from their laboratory window, Kirchhoff and Bunsen were thrilled to detect the spectral signatures of barium and strontium in the roaring blaze. It didn't take long for them to fathom that they could analyze the Sun and stars in a similar fashion, as light knows no distance in the voids of space. Light can be sent through a spectroscope whether it originates from a distance of one foot, ten miles, or a billion light-years away. Before this revelation, astronomers only knew that a star shines, that it occupies a certain position on the celestial sphere, and in some cases moves. But now they were acquiring the means to determine a star's composition and temperature, information once thought impossible to glean.
When an element is hot and glowing, it radiates its distinctive pattern of spectral colors. But at other times it can absorb those same wavelengths, which explains the origin of the dark lines that Fraunhofer found in the solar spectrum. Each element in the Sun's cooler outer atmosphere absorbs its designated colors, robbing the sunshine of those selected wavelengths before they arrive on Earth. The bright lines are simply the reverse of this process—the elements emitting those very same wavelengths of light as they fiercely burn. Either way—dark or bright—the pattern of lines indicates the presence of the element. Not until the early twentieth century, with the advent of atomic physics, did scientists come to understand this behavior as arising from the electrons in an atom jumping from one energy level to another, the atoms emitting bursts of light when they lose energy and gaining energy when they absorb the photons.
Astronomers quickly realized that, along with revealing a star's composition, a stellar spectrum could also tell them how the star was moving. In the 1840s the Austrian physicist Christian Doppler had surmised that the frequency of a wave, such as the tone of a sound wave or the color of a light wave, would be altered whenever the source of the wave moved. We've all heard the pitch of a siren rise to a higher tone as a police car or ambulance races toward us. This is the very effect that Doppler spoke of: The sound waves emitted by the screeching siren crowd together as they approach us, shortening their length and likewise raising the pitch. Conversely, as the police car pulls away, the sound waves stretch out, producing a lower pitch. In an analogous fashion, a light wave's length is shortened (gets “bluer”) when the source of the light approaches and is lengthened (gets “redder”) when the source moves away.
Astronomers, though, don't assess the overall color of a star or galaxy to measure its speed. That would be too difficult. They can more easily examine how the bright and dark lines in a celestial spectrum shift from their well-known laboratory positions. Depending on the object's motion, the lines can shift toward either the blue or red end of the spectrum. If a star or nebula, for example, is headed for us, its spectral lines move over toward the blue—that is, the lines get “blueshifted.” If moving away, the lines swing over toward the red and hence become “red-shifted.” The exact velocity is pegged from the amount of shift in the spectral bands. Blueshifts and redshifts are nothing less than the speedometers of the universe.
Keeler had the eye of a hawk in measuring how the celestial light entering his spectroscope was separated into its component wavelengths, with each spectral line offering enticing clues. He was America's leading practitioner of this new technique, with some of his best work being done on measuring the speeds of nebulae within the Milky Way. In Latin, nebulae is the word for “clouds” or “mist,” exactly what these extended objects look like through a telescope. Some are roundish and were dubbed “planetary nebulae” in the eighteenth century by British astronomer William Herschel, who thought they resembled planets through his telescope. Today, astronomers know that such circular nebulae are the result of aging stars casting off their outer envelopes. Other nebulae, such as the renowned Orion nebula, are more irregular and diffuse, made luminous by the new stars being born within these great cosmic oceans of gas.
By the late 1880s, as Keeler entered his thirties and continued these celestial explorations, he faced a career crisis. He was eager to marry Cora Matthews, the niece of Richard Floyd, the superviser of the observatory's construction and president of the Lick Trust. The couple had first met on the mountain but could not tie the knot right away because Lick officials would not provide them adequate housing at the observatory once married. There was also Keeler's growing dissatisfaction with director Holden, a tyrannical and humorless man who often tried to share credit for some of Keeler's discoveries and at times ordered the young man to carry out observations he was not eager to do. It was said that Holden, given his West Point background, ran the observatory “as though it were a fort in hostile territory,” barking out commands like a general under seige. On top of that, there was the tiresome isolation atop the mountain, with few opportunities to escape to the city and engage in a fuller social life. “I am a human being first and an astronomer afterwards,” Keeler confessed to a friend.
Faced with these growing concerns, Keeler began networking among his astronomer contacts and in 1891 secured the directorship of the Allegheny Observatory, a return to his first place of employment. His old boss Langley had by then moved to Washington, D.C., where he served as secretary of the Smithsonian Institution and was beginning work on his lifelong dream to successfully launch a flying machine.
In terms of telescope power, Keeler's transfer to the Allegheny Observatory, situated on a hill across the river just north of America's steel capital, was a giant leap backward. The weather was poorer, the air was tainted with Pittsburgh's industrial smoke, the atmosphere was more turbulent for viewing, and the observatory's main telescope was a 13-inch refractor, far smaller than Lick's 36-incher. Yet, in some ways it was a blessing. The constraints forced him to focus his astrophysical studies on such objects as nebulae, a less trendy territory and hence riper for discovery. Because of their larger size, compared to stars, the fuzzy objects could still be adequately examined, even with a smaller scope. Moreover, astronomical photography had become more efficient and convenient, allowing him to build up exposures and see spectral details he could not see before with his eye alone. He doggedly tracked down every new advance in spectroscopic and photographic equipment in hope of offsetting Lick Observatory's advantages. The experience, though exhausting, only enhanced his astronomical abilities.
From his new post in Pennsylvania Keeler eventually made headlines worldwide. He had been using his spectroscope at Allegheny to measure how fast some of the major planets, such as Venus, Jupiter, and Saturn, were rotating. Based on a method already used to gauge the Sun's rotation, Keeler knew that a spectral line in light arriving from the edge of the planet rotating toward us would be shifted toward the blue end of the spectrum; this same line would shift equally the other way, toward the red, when emanating from the edge, or “limb,” of the planet moving away. Along the way, Keeler cannily comprehended that he could also peg the velocity of Saturn's rings with the very same technique.
In 1856 the famous Scottish theorist James Clerk Maxwell had theoretically proven on paper that Saturn's rings were not solid, akin to a phonograph record, but rather composed of innumerable particles, little “moonlets” circling around in independent orbits. Saturn's immense gravitational pull, avowed Maxwell, would have torn apart any sort of solid disk. If true, then Newton's law of gravity would predict that the myriads of tiny chunks located in the outer part of the ring would be traveling slower than those closer in, nearer to Saturn's gravitational grip—just as Pluto, far from the Sun, orbits at a slower velocity than the solar system's inner planets.
A spectrum, taken on the night of April 9, 1895, gave Keeler the direct proof. The spectral lines indicated that the ring's particles were circulating around Saturn according to the rules of Sir Isaac. The ring was not a rigid plate after all. Within days, Keeler dispatched a report to the newly established Astrophysical Journal, and a torrent of newspaper and magazine articles about his triumph followed. His scientific reputation rose sharply, especially since he had devised such an elegant and simple test of Maxwell's conjecture, one that other astronomers knew they could have done years earlier, if only they had been so clever.
While Keeler was busy with Saturn, Lick director Edward Holden was scheming to expand his astronomical empire, by bringing the historic Crossley reflector to the observatory—a telescope first constructed by a Londoner, Andrew Common, in 1879. He had built it to test out some design ideas, even earning a gold medal from the Royal Astronomical Society in 1884 for the fine photographs taken with it, including the first image of a nebula, Orion. Its mirror was a glass disk, three feet wide, coated with a thin layer of silver, a relatively new development in reflector technology. Early telescopic mirrors had been made out of metal, which readily tarnished and easily got out of shape. Widespread use of reflecting telescopes did not occur until instrumentalists in the mid-nineteenth century learned how to cast large and sturdy glass mirrors, with the glass first ground and polished into an ideal shape for focusing the light and then its surface coated with a thin surface of metal for high reflectivity.
Satisfied with his design, Common was soon eager to make an even bigger scope and sold his award-winning instrument in 1885 to Edward Crossley, a wealthy textile manufacturer who moved it to his estate in Yorkshire. But after a few years, Crossley sadly deemed the English countryside unsuitable for decent astronomical observations and put the reflector (as well as the special dome he had built for it) up for sale in 1893.
Original Crossley telescope at the Lick Observatory
(Mary Lea Shane Archives of the Lick Observatory, University Library,
University of California-Santa Cruz)
Holden may have been a poor astronomer but he was a powerful persuader. He convinced the English tycoon to donate his entire assembly for free to the University of California, which now owned and operated the Lick Observatory. Once the parts for the scope and its dome arrived in 1895, Holden pushed mightily to get the system reassembled as soon as possible. As the dome was reconstructed on the edge of Ptolemy Ridge, a time capsule was inserted into its wall. The small zinc box, still hidden away, contains a letter from Crossley, the calling cards of the Lick astronomers then on staff, a Lick visitors pamphlet, and a set of U.S. postage stamps.
Lick astronomers, however, were not at all interested in this new addition to their astronomical arsenal. One disgruntled staffer declared the equipment “a pile of junk,” after some halfhearted attempts were made to put the telescope back into working order. For many, the Crossley was the last straw in a battle that had been raging for a very long time: a face-off between the director and his workforce. Tired of Holden's militaristic commands, hogging of the spotlight, and endless interference, the staff eventually revolted. Holden (described by Lick employees behind his back as “the czar,” “the dictator,” “that humbug,” “an unmitigated blackguard,” and “the great I am”) was forced to resign. The university regents had lost confidence in him. Holden took his final ride down “Lick Avenue,” the mountain's dusty road, on September 18, 1897. Only one person, a young assistant, went out to say good-bye.
Keeler, by this time, was getting restless back in Pennsylvania. The mighty iron and steel mills in the Pittsburgh area were expanding, dirtying up his sky even further with the black soot of their coal fires. And, though he was noted as the country's most able spectroscopist, Keeler was more and more hampered by his tiny 13-inch refractor, a telescope originally built forty years earlier for amateur viewers. Its aging lens absorbed the higher wavelengths of light—blue and ultraviolet—which limited him to work primarily in the yellow-red region of the spectrum. To make matters worse, his former assistant at Lick, William Wallace Campbell, had arranged for Lick to get a new spectrograph (an instrument that not only disperses the light into its constituent colors but records the spectrum as well). It was being built in Pittsburgh, and Keeler had agreed to test it out before it was shipped to California. The experience made him realize that it would soon be impossible for him to compete with Lick, especially since a great economic turndown, a depression that started in 1893 and lasted for years, had dried up sources of funds to expand his facility and raise his salary. Holden's firing came at an opportune time for Keeler.
In the search for Holden's replacement, a number of names came into play, including the venerable Simon Newcomb, George Davidson, who had originally coaxed Lick to fund the observatory, and several senior Lick astronomers. Keeler was added to the mix as a dark horse but soon became a favorite among the more progressive university regents. They wanted someone young, someone with impressive credentials, who would help the University of California achieve first-class status. Keeler won the vote by 12 to 9, Davidson coming in second.
Hearing that they might lose their director, Allegheny Observatory supporters launched a last-minute effort to raise enough funds from the Pittsburgh elite to build a new edifice for Keeler, one equipped with an imposing 30-inch telescope. Poems were even written and printed in local newspapers to boost the cause:
“Stay with us, Keeler,” so they say,
“And twice as much as Lick we'll pay.”
Wherefore perchance he'll not resign
But stay and keep our stars in line.
If the full amount required had been raised, Keeler would likely have stayed, not wanting to be disloyal to a town he had come to love. But the campaign fell short (to the relief of his wife, who longed to return to the sunny climes of the West Coast). Yerkes Observatory, in Wisconsin, home to the newest record-holding telescope, a 40-inch refractor, also made him a job offer but could not guarantee a permanent staff position. Keeler, anxious to advance both his research and professional career, at last telegraphed his acceptance of the Lick directorship to University of California officials. It was a time when the United States was finally emerging from its deep economic depression. Hope and optimism were on the rise, as the nation was attaining status as a world financial power, at last surpassing Great Britain in overall worth. Highways were being paved with asphalt, and cities brightly glowed at nighttime, awash in electric light. Telephone and telegraph wires lined urban streets like thick, artificial spiderwebs. Keeler's vocation was carried forward on the swelling tide.
Keeler went back to Mount Hamilton, or the “hill,” as it was affectionately known to its residents, on June 1, 1898, seven years after he had first departed for the East Coast. There he found his new duties resembling that of a small-town mayor. “It [was] like being shipwrecked on an island,” recalled Kenneth Campbell, who had grown up on the mountain while his father, William, was on staff. “The Director of the Observatory was, I would say,…the czar… He had to see that Mrs. MacDonald didn't break her leg on that back step, as well as worrying about spiral nebulae.” By then the complex housed three senior astronomers, three assistant astronomers, a small group of workmen, and assorted spouses, servants, and children, some fifty people in all. If a hostess sent out an invitation for an evening gathering, it was plainly understood: no clouds in the sky, no party. Astronomy always came first. A new teacher for the one-room schoolhouse was hired nearly every year (as she often ended up marrying one of the astronomers). For relaxation, residents took some clubs over to the rudimentary golf course, eight holes laid out by one of the senior astronomers on a stretch of flat land just below the mountaintop. No need for man-made hazards; they were all natural—ditches, ridges, ravines, and rock formations; the “greens” were oiled dirt. Occasionally a ground squirrel would carry off a ball, mistaking it for a tasty nut.
A biologist visiting Mount Hamilton returned to the valley below feeling as if he had “dwelt awhile upon Mount Sinai,…watched the marshalling of the stars and the dividing of the constellations.” Saturday nights were often held aside for visitors, with loaded stages and buggies coming up the mountain sometimes twenty to thirty in procession. Leaving San Jose, the wagons could take up to seven hours to traverse the twenty-five serpentine miles, passing first through orchards of figs, oranges, olives, and peaches. Always in sight during the slow ascent were the observatory's bright white domes. Not until 1910 did the automobile reduce the travel time to two hours.
Keeler resided with his wife and two children, Henry and little Cora, in part of a three-story residence known as the Brick House, just a stone's throw from the main building, where the telescopes were located. The move to Lick decidedly changed his routine. His research was now curtailed by innumerable administrative duties, especially correspondence with university officials, suppliers, prospective students, colleagues, and the general public. “There are no astronomical phenomena expected to accompany, or precede, the second coming of Christ,” he politely responded to one correspondent. In style and temperament, Keeler was the anti-Holden. “No member of the staff was asked to sacrifice his individuality in the slightest degree,” said Lick astronomer W. W. Campbell. “No one's plans were torn up by the roots to see if they were growing… Keeler's administration was so kind and so gentle, and yet so effective, that the reins of government were seldom seen and never felt.”
Science, though, remained Keeler's prime objective in accepting the directorship. He once again had access to large telescopes situated in a premier environment for viewing, far removed from polluted industrial air. He completed his first paper, the spectral analysis of a peculiar star's outer envelope, within a month of his arrival. For this, he used the famous 36-inch refractor. As director, Keeler could have wielded his power and become the prime user of the 36-inch, but instead he made a daring and momentous decision. He decreed that Campbell, who had become Lick's main spectroscopist during Keeler's absence, would continue using the 36-inch to carry out an ambitious project Campbell had already begun, measuring the velocities of the stars. Keeler, to everyone's astonishment, chose to work on something completely different: getting the disreputable Crossley reflector up and running.
Keeler became interested in reflecting telescopes while he was still director of the Allegheny Observatory. He knew such telescopes would be particularly advantageous for carrying out his specialty—spectroscopy. The thick glass lenses in refracting telescopes tended to absorb certain wavelengths selectively (depending on the glass and lens construction), keeping that light from registering on either the eye or a photographic plate. This was a dismaying effect to a spectroscopist, who was devoted to collecting each and every light wave emanating from a celestial object. Mirrors, on the other hand, didn't have this problem. They shepherded all light waves equally, no matter what the color, right to the focus. Moreover, lenses were reaching their maximum size at the end of the nineteenth century; they couldn't be manufactured much bigger than forty inches without getting distorted by their own weight. Mirrors, on the other hand, could be made much larger. In Keeler's estimation, reflecting telescopes had acquired a stigma in the past because they had been placed in cheap, flimsy mounts.
Keeler had seen the power of reflectors firsthand while visiting England in 1896 and attending a meeting of the British Association for the Advancement of Science. There Isaac Roberts, a former businessman and accomplished amateur astronomer, displayed the eye-catching photographs taken with his 20-inch reflector. Roberts had pioneered many of the techniques for taking long-term exposures and was the first to reveal that the Andromeda nebula was a spiral. Photography was then having a tremendous impact upon astronomy, radically transforming its procedures. Holden, right before Lick opened, wrote that astronomers can now “hand down to our successors a picture of the sky, locked in a box.” Observers were able to continue their research at their office desks, analyzing their images with mathematical precision, no longer dependent on crude drawings, hasty notes in a logbook, or the fading memory of their night at the telescope. Changes in a celestial object could at last be accurately monitored, from year to year and decade to decade.
After the palace revolt against Lick's former director, the Crossley had been abandoned. It was the mountain's white elephant. No Lick observer was interested in using the reflector, not a surprising turn of events given its dreadful reputation. Even before Holden left, a staff astronomer had written a long memorandum summarizing what sort of research could be done with the Crossley. The title of his paper broadcasted the answer with unforgiving bluntness: “No Work of Importance.”
Keeler thought otherwise, even though he had never before used a reflecting telescope. He was interested because he was after rare game: the particular stars and nebulae that had eluded previous spectroscopists due to their faintness, and the Crossley's special features were going to allow him to obtain a decent spectrum. The Crossley was not just any telescope mirror; it was the largest of its kind in America, but Keeler faced innumerable engineering problems, which he had to solve before the Crossley would be fully functional. For one, the spectrograph he inherited was so large that it had to be removed from the telescope each time the dome needed to be shut. And the telescope's mounting, originally set so it would correctly track the stars in England, had to be realigned to account for Mount Hamilton's more southerly location. Then there was the need for a new eyepiece, as well as a drive clock to keep the telescope in sync with the moving sky. Chemicals had to be gathered for silvering the yard-wide mirror—silver nitrate, caustic potash, ammonia, and a reducing solution composed out of rock candy, nitric acid, alcohol, and water—and telephone wires extended from nearby astronomers' cottages to the dome, so there would be electric light to illuminate the guidewires in the eyepieces.
Making improvements in fits and starts—three steps forward, two back—Keeler and his associates at last got the telescope operating tolerably in September 1898, just four months after he arrived back at Lick. On the fifteenth of that month he tried out his camera for the first time. His opening target, Altair, the brightest star in the constellation Aquila, was out of focus, but another exposure, east of the star, was better. “The fainter stars look pretty sound, but the brighter ones show irregularities,” he wrote down in his logbook. Two weeks later he took a photograph of the Moon, then nearly full. “Plates are fairly good,” he briefly noted. Inside the Crossley dome, the upper wall was painted black, in order to absorb stray reflections from the sky; the lower half, though, was colored bright red, so Keeler and his assistants could see where they were going in the dark. The whole interior was bathed in the faint glow from a lantern fitted with panes of crimson glass, as the photographic plates were not sensitive to red light. Such precautions were essential since the Crossley mirror was held by an open framework of iron rods instead of mounted within an enclosed tube.
In late fall Comet Brooks appeared in the sky. This led to Keeler's first research paper based on his observations with the Crossley. His images, taken over eleven consecutive nights with the help of his assistant Harold Palmer, displayed finer details than previous photographs of comets. They even captured a double nucleus. “On the negative of November 10, obtained with an exposure of 50 [minutes],” reported Keeler, “the head of the comet is made up of two clearly separated nebulous masses, surrounded by the nearly circular coma…. I am inclined to believe that the division of the nucleus was real.” Keeler was not the first to discern such cometary structure, but it was exciting nonetheless.
He soon was observing the Pleiades, the impressive cluster of stars (the “Seven Sisters”) situated near the constellations Taurus and Orion in the autumn nighttime sky. Taking a series of photographic exposures, sometimes lasting longer than an hour, he was able to show that the Pleiades is embedded in filamentary and diaphanous clouds of gas. “Nebulous wisps…are characteristic of the region,” he reported. He later wowed astronomers with a spectacular photograph of the Orion nebula, convincing them of the capability of a reflecting telescope to bring out features formerly too faint to discern. The stunning image served as the frontispiece for an issue of the Publications of the Astronomical Society of the Pacific, and it amazed even him. “The photographic power of the Crossley reflector on a fine night is surprising,” he wrote, “at least to one who has hitherto worked with refractors only.”
Keeler went on to use the Crossley to record other arresting celestial sights, such as the sinuous and radiant strands of the Lagoon, Omega, and Trifid nebulae. “We know them so well today,” Osterbrock pointed out, “that it is hard for us to realize how sensational his photographs were to the astronomers of his time… They showed much more detail than even the best drawings of the earlier visual observers.” Keeler was generating the Hubble Space Telescope pictures of his time.
Outside his duties as Lick director, Keeler was spending all his available time on Ptolemy Ridge, becoming the world's expert on nebulae. “The [Crossley's] workmanship is poor and the design is clumsy, but on a fine night the photographic power is quite extraordinary. It has seemed to me worth while to devote some time to ordinary photography of nebulae, as nothing that I have yet seen in this line comes up to what I can get with the Crossley,” he told a friend.
The week before and the week after the new Moon, when the lunar orb was in inky shadow, were his best viewing times. Only then was the sky dark enough to photograph the faint nebulae he was beginning to detect, without interference from a bright lunar spotlight. When the night was clear and calm, he often had time to take several exposures. But then there would be stretches, even when the sky was cloudless, when the wind was so strong that the Crossley shook on its mount, ruining his observation.
Keeler at last got around to his first spiraling nebula on April 4, 1899. He started off with one succinctly named M81, situated in the constellation Ursa Major, just above the “pot” of the Big Dipper. He carefully tracked it from nine until eleven o'clock that evening, as two hours were needed to gather enough light to record an image on the plate. Once the plate was developed, he right away noticed a faint spiraling but considered it “valueless.” A misalignment of the telescopic axis had unfortunately led to the stars appearing as small arcs.
His luck was better the following month. With the Crossley fixed, he took several photos of M51, known as the Whirlpool for its wondrous view of the spiraling, face-on. Keeler's four-hour exposure captured aspects of the nebula never before seen, largely due to the steady air above Mount Hamilton. Keeler sent a transparency of this exposure to his friend George Ellery Hale, director of the Yerkes Observatory, where it took Hales breath away. “Everyone in the Observatory considers [this picture] to be far superior to anything of the kind they have ever seen or expected to see,” Hale responded enthusiastically.
There was something even more consequential in the image, although Keeler didn't appreciate the import right away. Surrounding M51 in the picture were seven more nebulae—though smaller and fainter. In a brief note to the Royal Astronomical Society in London, he listed the exact locations of these nebulae and described them. Some were round, others spindle-shaped or elongated. And that was only the beginning. “Several other faint nebulae, the positions of which were not noted, were observed during the search,” he wrote. “In fact, this region seems to be filled with small, apparently unconnected nebulae, large numbers of which would doubtless be revealed by long-exposure photographs.” It was a fascinating find, but he just assumed it was an uncommon grouping of nebulae, likely confined to that sector of the sky.
Photo of Whirlpool galaxy (M51) taken by James Keeler in 1899 with the
Crossley telescope. One faint nebula seen in upper left.
(Copyright UC Regents/Lick Observatory)
When a selection from Keeler's growing archive of pictures was prominently displayed at the Third Conference of Astronomers and Astrophysicists, held at Yerkes in September 1899, it created great excitement. Astronomers formerly skeptical of a reflector's value, such as E. E. Barnard, began to change their opinion. Barnard, who had fled from Lick to Yerkes during the Holden debacle, just stood in front of Keeler's photographs for hours, taking in every scrumptious detail of the Orion nebula, the Pleiades, and the M51 spiral.
Media savvy, Keeler knew the value of a good pitch in helping both the observatory and his career. After a well-publicized solar eclipse, he had advised a fellow astronomer, who was about to convey his eclipse observations to a conference, to dwell “on the successes rather than on the failures. If you were to tell a reporter that three plates out of ten were failures, he would receive a totally different impression from what he would if you gave him the equivalent statement that seven out of ten plates were successes.” Keeler sent copies of his best pictures to the Royal Astronomical Society, the New York Academy of Sciences, and the American Philosophical Society in Philadelphia, all institutions that could influence opinions within the scientific community. He also made sure that Crossley, the reflector's former owner, received a particularly nice print of the Orion nebula. “The finest I have ever seen,” replied the English businessman. “It proves to me how important it is not only to have a powerful instrument but also a site where it can be used to the greatest possible advantage.” Getting his results widely distributed seems to have paid off for Keeler. In 1900 he was elected to the National Academy of Sciences, a year after he had received its prestigious Henry Draper Medal for astrophysical research. He was now one of America's leading astronomers.
In late summer, right before the Yerkes conference, Keeler had started to examine the faint nebulae more closely. He took a one-hour exposure of NGC 6946, a fuzzy patch first noticed by astronomer William Herschel at the end of the eighteenth century and listed as the 6,946th object in the New General Catalogue, published by J. L. E. Dreyer in 1888. Upon developing his plate Keeler saw immediately that it was yet another spiral, similar to M51 and M81 but smaller in size. A few nights later he examined two more fuzzy nebulae. Again he found, in each case, spiraling arms wrapping around a brightened center. All these dim nebulae appeared to be flattened disks, much like the Andromeda nebula, but they were set in different orientations.
And something more surprising developed as this work progressed. Each time Keeler took a photograph, he found even fainter nebulae loitering in the background of his image. At the start of his venture, when he first saw the seven nebulae on his plate of M51, he thought it “a rather remarkable number of nebulae to be found on a plate covering only about one square degree.” That's a segment of the sky the size of two full Moons. But he soon discovered that this celestial flock wasn't so remarkable after all. With each additional picture Keeler took, he detected more and more nebulae arrayed over the heavens. Throughout the fall of 1899, whenever the nighttime sky was clear and moonless, he made his way to the Crossley and kept adding to his count. He took a four-hour exposure of NGC 891, a spiral seen edge-on, and the plate revealed thirty-one new nebulae, scattered around the central spiral like background extras in a movie scene. On a photograph of NGC 7331 he saw twenty more and “there are nearly as many on several other plates,” he reported. “Besides these new nebulae…the plates contain a considerable number of objects which are probably nebulae so small that the resolving power of the telescope is insufficient to define them in their real form and to bring out their true character.”
Keeler was dumbfounded. Space was awash with tiny nebulae, and most of them displayed a conspicuous spiral form, though seen from assorted angles. “There are hundreds, if not thousands, of unrecorded nebulae within reach of our 36-inch reflector,” reported Keeler. By assuming that there were three new nebulae in each square degree (a number he admitted was far too conservative), he estimated that “the number of new nebulae in the whole sky would be about 120,000.” He was positive there were more. Before this, about nine thousand nebulae had been cataloged by astronomers but only seventy-nine were identified as spirals, less than 1 percent. The Yerkes Observatory, in Wisconsin, by then had opened to great fanfare with a bigger telescope, one with a lens forty inches in width, but it still could not compete with Keeler's reflector. Even Barnard conceded that his new home at Yerkes, situated at a more lowly thousand feet above sea level, was “a mirey climate for a great telescope and discoveries are few and far between.”
Keeler's 1899 image of NGC 891 with background nebulae marked
(Copyright UC Regents/Lick Observatory)
In an article in Astronomische Nachrichten, a highly respected German astronomical journal, Keeler drew attention to his baffling finds: “The spiral nebula has been regarded hitherto as a rara avis—a strange and unusual phenomenon among celestial objects, to be viewed by the observer with special interest, and marked in catalogues with exclamation points… But so many other nebulae also proved to be spirals that the classification…soon lost its significance… The same form occurs over and over again, on a smaller scale, among the fainter nebulae.” Spirals were now the norm, not the exception, in the celestial sky. Keeler figured they must be an important constituent of the universe, ranging in size “from the great nebula in Andromeda down to an object which is hardly distinguishable from a faint star disk.”
But what in blazes was a spiral nebula? No one knew for sure, solely because there was as yet no way to determine the distance, a recurrent problem for astronomers. If the spirals were nearby, part of the Milky Way, then they would be relatively small given their size in the sky, each possibly a new star forming. But if the spiraling patches were very far away, then they would have to be huge to appear as they did in telescopic photographs, as big as the Milky Way itself.
To Keeler, the whirling shape seemed to indicate that the object, whatever its nature, was rotating. And like many of his contemporaries, he speculated that the spirals were somehow linked to star formation. “If…the spiral is the form normally assumed by a contracting nebulous mass,” he pondered, “the idea at once suggests itself that the solar system has been evolved from a spiral nebula.” Given this view, each spiral then marked the spot where a new star and its planetary companions were hatching. The idea that our solar system condensed out of a rotating nebula of gas had already been introduced by both Immanuel Kant and Pierre-Simon de Laplace decades earlier. In a lecture at Stanford University, Keeler made this very point: “The heavens are full of beautiful illustrations of the views of Laplace…[in] photographs of great spiral nebulae in various stages of condensation, taken recently with the Crossley reflector at the Lick Observatory.”
Much as Einstein's relativity inspired numerous works of art and literature since its inception, so too did the nebular theory in the nineteenth century, as seen in this stanza from “The Princess,” by Great Britain's poet laureate Alfred Lord Tennyson in 1847:
This world was once a fluid haze of light,
Till toward the centre set the starry tides,
And eddied into suns, that wheeling cast
The planets …
It's interesting to contemplate how far Keeler might have gone in this line of research. With his phenomenal skill at the telescope, he had a good shot at obtaining spectral data that forced him to consider other explanations for the nature of the spiral nebulae. “Keeler…was a far better trained, more experienced spectroscopist than any [other astronomer of his time]. No doubt he would have reached the conclusion that the spirals were galaxies of stars,” contends Osterbrock, himself a Lick Observatory director seven decades after Keeler. Keeler might have also noticed, far earlier than others, that the spirals were racing away from the Milky Way at high velocities. He had the smarts, and he had the equipment. He had already obtained the velocities of myriad planetary nebulae and had a plan to move on to the spirals. His friend Hale had that impression; he was sure that Keeler intended to “follow up his remarkable beginnings with the Crossley reflector, cataloging the new nebulae, and doing something with their spectra.”
But we will never know, for Keeler died unexpectedly on August 12, 1900, one month shy of his forty-third birthday. Throughout the spring and summer of 1900 Keeler had been suffering from what he called “a hard cold.” An entrenched cigar smoker since his college days, he had already been experiencing heart problems. His doctor also diagnosed pleurisy of the lung, “nothing very serious,” Keeler told friends, but he was likely afflicted with either emphysema or lung cancer. He couldn't manage walking the steep rise from the Crossley reflector back to his home without stopping several times short of breath. With his doctor forbidding him to continue observing, he left the mountain at the end of July for a short rest with his family. He was expecting to return to use a new spectrograph, just completed for the Crossley, and begin examining spiral nebulae. But within weeks Keeler died in San Francisco, after experiencing two strokes. The setback for astronomy, said his friend and colleague Campbell, was “incalculable.” Harvard College Observatory director Edward Pickering wrote that the “loss cannot be overestimated… There was no one who seemed to me to have a more brilliant future … or on whom we could better depend for important advances in work of the highest good.” The journal Science ran a tribute to Keeler on the first page of its September 7, 1900, issue.
On Mount Hamilton, the memory of Keeler became sacrosanct and remains so to this day. He was the ideal director, an astronomer without equal cut down in his prime. But Keeler's acclaimed reputation beyond the Lick Observatory grounds gradually faded. In encyclopedias he is primarily remembered (if he is mentioned at all) for his work on Saturn's rings, with only a brief reference to his pioneering use of a reflecting telescope at high altitude, which allowed him to record the myriad spiral nebulae. Yet his tenacious pursuit of the nebulae with the Crossley reflector is truly his most lasting legacy. “The day of the refractor was over,” said Osterbrock, “and although a few more intermediate-sized ones were built, no American professional astronomer ever thought seriously of building a very large telescope as anything but a reflector, after Keeler's work with the Crossley.”
With his innovative spirit and success in restoring a once-despised instrument, Keeler pushed reflectors to the forefront of astronomical research. Campbell, who had been carrying out his program to map the motions of the stars, knew that Lick needed a second telescope in the southern hemisphere to complete the observations. Chosen as Keeler's successor to the directorship, he decided to build another 36-inch reflector, similar to the one that Keeler so successfully got working. In 1903 this telescope was erected on a site outside Santiago, Chile, where it was in operation for twenty-five years. The refractor at Lick had cost hundreds of thousands of dollars; Campbell built his Chilean scope for a thrifty $24,000.
In the fall of 1901, just a year after Keeler's death, the Yerkes Observatory assembled a trial reflector of its own in one of its small domes. With a mechanical system far superior to the Crossley, which allowed the mirror to be highly stable, this Yerkes reflector yielded photographs of nebulae that were even better than Keeler had obtained, despite its smaller 24-inch aperture. “The results obtained with the two-foot reflector show that very fine atmospheric conditions are necessary for the best results,” reported the telescope's builder, George Ritchey. “It is interesting to think of the photographic results which could be obtained with a properly mounted great reflector in such a climate and in such atmospheric conditions as prevail in easily accessible parts of our country, notably in California.”
Keeler not only turned reflectors into astronomy's instrument of choice, he inspired astronomers to take a new look at the universe. Was the cosmos defined as simply the Milky Way, or was there more to the universe than met the unmagnified eye? Keeler took a problem previously tackled by amateurs, for the most part—the spiral nebulae—and turned it into a prime concern for professional astronomers. He gave traditional astronomy a good shake at the end of the nineteenth century and in the process reinvigorated a debate that had been going on for centuries. What was the true nature of those irresolvable nebulae—so mysterious, so enthralling—that pervaded the celestial sky? Could the universe possibly be far larger?