The Day We Found the Universe - Marcia Bartusiak [69]
Starting in November 1917 Shapley fired off, with great rapidity, his next group of papers. In his ongoing series on the globular clusters, he completed articles six through twelve in just six months. It was as if he were back at his old newspaper job, pounding out an exclusive on his typewriter to meet a daily deadline. The first of these papers announced his grand goal straightaway: He intended to report on nothing less than “the general plan of the sidereal system…bearing on the structure of the universe.” Shapley made this bold claim because, while trying to make sense of all his data, he had a revelation. He came to believe that his observations were not only refashioning the Milky Way but the universe as well. Unlike many of his fellow astronomers, he was fearless at making extravagant leaps in speculation.
At this stage Shapley had finished slogging through his many observations and calculations and had plotted the positions of the sixty-nine known globulars onto a graph. This provided him with a feel for how they were distributed through space in three dimensions. The result, he noted in paper number seven, was “striking.” Most of the clusters resided in one particular direction, over by the constellation Sagittarius. Like moths lingering by a streetlamp, they were symmetrically arranged about a spot rich in stars and nebulae within our galaxy. It was said the star clouds in this region were so thick that it was “impossible to count every star shown; the images of the faintest stars…merged into one another forming a continuous gray background.” The galactic coordinates for this spot did not match those for our solar system. The globular clusters were not arranged around the Sun at all (as might be expected). Good old Sol was situated off to the side—by Shapley's initial estimate around 20,000 parsecs, or 65,000 light-years away.
Other astronomers had noticed this peculiar distribution of the globular clusters before. In 1909 the Swedish astronomer Karl Bohlin even dared to suggest that the center of the galaxy was in that direction, with the clusters all huddled around it. But no one at the time, including Shapley, took this idea seriously. It was just assumed that the solar system resided in the heart of the galaxy (or close to it). Now Shapley was confirming what Bohlin had suspected all along. His observations forced him to radically alter his original opinion.
From this point on, Shapley's progress was swift. Papers eight through eleven, submitted for publication in December and January, provided the technical details on his methods, assumptions, and calibrations. Shapley knew his conclusion was going to be revolutionary, so he stacked his ammunition with orderly care. Page by page he was stepping toward his grand finale. The full-scale assault took place with paper number twelve, titled “Remarks on the Arrangement of the Sidereal Universe.” This particular article was not fully ready for submission to the Astrophysical Journal until April, in the waning days of World War I, but Shapley couldn't wait that long to spread the news. On January 8, 1918, he wrote the noted Arthur Eddington in England that “now, with startling suddenness and definiteness, [the cluster studies] seem to have elucidated the whole sidereal structure”—in other words, the architecture of the Milky Way. Not only were the globular clusters uniformly scattered around the center of the galaxy, with the Sun shoved off to the hinterlands, but the Milky Way was far larger than anyone had formerly presumed. Shapley now gauged it was an