The Day We Found the Universe (7 page)

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.”