The Day We Found the Universe - Marcia Bartusiak [104]
Hubble was far more vocal and forthright, though, about his observational plans. In February 1922 he sent a lengthy, typewritten letter to Slipher, a member of the Committee on Nebulae for the International Astronomical Union, on his long-term strategy for studying the nebulae. It was going to be an all-out attack. Hubble planned to determine their structure, peg their distribution across the heavens, and measure their dimensions. And as a stealth advocate of the island-universe theory, Hubble wanted to obtain undeniable proof that stars—vast collections of stars—resided in the spiral nebulae. He knew that finding novae were crucial in doing this and urged the IAU that “half a dozen of the largest spirals in addition to Andromeda should be followed carefully for novae.” Major Hubble was now applying his lessons on military tactics to conquering his astronomical targets.
“I must confess that I am rather dazed by [Hubble's] letter,” said Lick astronomer William H. Wright, who had also received a copy of Hubble's agenda. “One can see that the nebulae will have no private life when he has his way. Hubble is a great lad, and I only hope that he will have the strength and energy to carry out a fraction of the work he would like to see done.”
Hubble, who had just gained a seat on the committee, was particularly fired up about a nebula classification scheme he wanted the IAU to adopt. To Hubble, properly categorizing the nebulae was an essential first step in determining their physical nature. By 1923 he had divided the nongalactic nebulae into two categories: the ellipticals and the spirals. An elliptical was an amorphous blob shaped somewhat like an egg. The spirals, of course, were the stunning pinwheels. If the bright center of the spiraling disk was a round bulge, he called it a “normal spiral;” if elongated, a “barred spiral.” The nongalactic nebulae that didn't fit either class, like those resembling the chaotic Magellanic Clouds, were tagged “irregulars.” But the IAU committee dragged its feet on Hubble's naming system and desired some changes, a rebuke that may have had long-term effects. At one point in the long wait, Knut Lundmark published a similar scheme, which enraged Hubble. He accused the Swedish astronomer of plagiarism. Afterward, Hubble was never keen to work on committees, attend general astronomy meetings, or share in collaborations. With a few exceptions, he tended to work alone. There might have been another reason for this as well. Though displaying a commanding public presence, Hubble was actually “pathologically shy around colleagues with whom he had little… contact,” contends Allan Sandage, who knew Hubble in his later years. Hubble proceeded to classify the nebulae in his own way and over time his arrangement was eventually accepted by the astronomical community.
Throughout 1923, over a total of forty-seven nights on the mountain, Hubble used both the 60-inch and 100-inch telescopes to survey a variety of nebulae around the celestial sky. He was on a reconnaissance mission. Though scarcely any nebulae were repeated, he did pay special attention to NGC 6822, a nebula in Sagittarius first discovered in 1884 by his former Yerkes colleague E. E. Barnard. The nebula stood out from the pack because it looked strikingly similar to the Magellanic Clouds in the southern celestial hemisphere.
The 100-inch and 60-inch telescopes (left, right) side by side on Mount
Wilson (Courtesy of the Archives, California Institute of Technology)
By July Hubble found five variable stars in NGC 6822 and informed Shapley at Harvard, suggesting that Shapley investigate the object on the plates stored away at the Harvard observatory. “What a powerful instrument the 100-inch is in bringing out those desperately faint nebulae,” responded Shapley. “As for N.G.C. 6822, I think there is no doubt but that it is another star cloud like the Magellanic Cloud.” Although there was no love lost between