The Day We Found the Universe - Marcia Bartusiak [36]
Curtis first spent time getting to know the Crossley's strengths and weaknesses: What were the faintest stars it could photograph? How many hours of exposure were required? He had the good fortune to start his new venture just as a famous celestial visitor, Halley's Comet, visibly reappeared in the skies in 1910, as it did every seventy-six or so years, providing a superb target to test out the Crossley's photographic abilities. The comet this time passed relatively close to Earth, creating quite a stir throughout the world, so by the time it completely disappeared from telescopic sight in 1911, the Crossley and other Lick telescopes had taken nearly four hundred pictures of its spectacular passage.
With the Crossley checked out, Curtis at last turned his attention to the mysterious nebulae. Keeler and others at Lick had previously amassed a photographic library of around one hundred nebulae and clusters using the Crossley. By the summer of 1913, Curtis boosted that number to more than two hundred. “Many of these nebulae show forms of unusual interest,” he jotted down in his observatory report. “The great preponderance of the spiral form becomes more and more striking with the progress of the survey.” He was beginning the process of identifying and cataloging the nebulae, particularly the spirals, in hope of detecting patterns that would lead to revealing what they were. His descriptions conveyed the rich diversity in their appearance: A spiral could be either “patchy,” “branched,” “irregular,” “elongated oval,” or “symmetrical.” For the moment, he was merely recording what he saw, not venturing to discuss what they might be.
It was tiring work. “Crossley still has its old reputation of using up more energy than any other instrument on the hill,” Curtis told a colleague. Despite the improvements he had made on the telescope, it was still difficult to reach the eyepiece at certain positions. “If you got a little bit sleepy at night, it was dangerous, because it went down a great many feet [from the observing platform] to a floor in the basement,” said one of the telescope's later users. One wisecracker suggested the only way to observe with the Crossley in comfort was to fill the dome with water and observe from a boat.
When he first started his study, Curtis assumed that the spirals were comparable to the size of a modest cluster of stars, spanning no more than several hundred light-years in width. It was a reasonable assumption. Over at the Mount Wilson Observatory, with its new 60-inch reflector, George Ritchey had begun to photograph the spiral nebulae and was concluding they were a mix “of smooth nebulous material and also of soft star-like condensations or nebulous stars.” He surmised he was seeing a collection of developing stars—a good-sized cluster but certainly not an entire “island universe.”
But Curtis began to doubt this viewpoint as he gathered more evidence with the Crossley. Some of the first hints surfaced when he rephotographed a number of nebulae that Keeler had previously imaged. By comparing his most recent spiral pictures with those gathered years earlier, he hoped to see how the swirling clouds had rotated. The amount of motion measured was going to help him judge their distance. But Curtis didn't detect any sign of movement, not a smidgeon “rotatory or otherwise,” he reported. “As the spirals are undoubtedly in revolution—any other explanation of the spiral form seems impossible—the failure to find any evidence of rotation would indicate that they must be of enormous actual size, and at enormous distances from us.” It would simply be impossible to measure a shift by sight alone if the spiral were considerably larger and at the same time pushed far off into space.
An edge-on galaxy photographed by Heber Curtis in 1914,
showing the dark lanes of dust and gas within the disk
(Copyright UC Regents/Lick Observatory)
Even earlier Curtis started reporting that some of the spirals he photographed—the ones so tilted they were seen edge-on—resembled “the Greek letter Ф… for lack of a better