The Day We Found the Universe - Marcia Bartusiak [47]
By February Slipher came to trust both his instrument and his expertise (which in hindsight was truly incredible; today, with far better equipment, astronomers measure Andromeda approaching us at 301 kilometers per second, a difference from Slipher's rate of less than a third of a percent). Slipher informed Lowell that the plates “agree as closely as could be expected and I can not doubt the reality of the displacement.” Andromeda had to be moving at an astounding clip. Instead of announcing the result in a major astronomical journal, though, Slipher chose to publish his brief account—just nine paragraphs—in the Lowell Observatory Bulletin. True to form, Slipher held off on any grander statement until he had secured some confirmation.
Yet even one spiral nebula velocity was an exceptional accomplishment. Many were thrilled for Slipher. “It looks to me as though you have found a gold mine,” wrote Miller, “and that, by working carefully, you can make a contribution that is as significant as the one that Kepler made, but in an entirely different way.”
Max Wolf at the Königstuhl Observatory in Heidelberg admired the spectrum's “beauty.” Edwin Frost, then editor of the Astrophysical Journal, wrote his sincere congratulations at the revelation of such an “incredible” velocity. “It is hard to attribute it to anything but Doppler shift,” he said. “Your success on this object indicates the value of elevation above the sea…. It is a pity that someone cannot try other objects of this sort at elevations of 12,000 to 15,000 ft.” Astronomers would, but only decades later.
Then there were others, such as Campbell at Lick (predictably), who were highly skeptical. “Your high velocity for [the] Andromeda Nebula is surprising in the extreme. I suppose…the error of [your] radial velocity measurement may be pretty large. I hope you have more than one result for velocity.”
To be fair to Campbell, an extraordinary finding like this needed extraordinary proof, and Slipher knew that as well. He had already put out the call for others to try to confirm it. Within a year, Wolf was able to follow up. His spectrum was cruder but still in fair agreement. Soon after, even persnickety Lick Observatory came to confirm Andromeda's fleetness. Lick astronomer William H. Wright obtained a velocity that nearly matched Slipher's. “I had planned to get at this work years ago when Fath got his big displacement… but you seem to have beaten me to it,” Wright told Slipher.
Lowell was enormously pleased. “It looks as if you had made a great discovery,” he wrote, right after Slipher's initial finding. And then the director added, “Try some more spiral nebulae for confirmation.” Slipher took up the challenge with great enterprise, for he was better at following directions than initiating his own scientific pursuits.
Working on Andromeda, though, was a holiday compared to gathering the spectral light from other spirals. Though its center is barely discernible to the naked eye, Andromeda is still the biggest and brightest spiral in the nighttime sky. The others only get progressively smaller and dimmer, which made it even harder for Slipher to obtain their velocity. “Spectrograms of spiral nebulae are becoming more laborious now because the additional objects observed are increasingly more faint and require extremely long exposures that are often difficult to arrange and carry through owing to Moon, clouds and pressing demands on the instrument for other work,” he noted in his work papers. The job for him was “heavy and the accumulation of results slow.”
Slipher's first target after Andromeda was M81, a spiral that is brighter than most, and then he looked at a peculiar nebula situated in the Virgo constellation known as NGC 4594. In his notes, he described it a “telescopic object of great beauty.” It's now popularly known as the Sombrero galaxy for its distinctive resemblance to a Mexican hat viewed from the side. Slipher eventually saw that NGC 4594 was moving at a speed “no less than three times that of the great Andromeda Nebula.” This time, however, the nebula