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its wonderful rings, its belts, its satellites, shone with a splendor and distinctness of detail never before equaled.” Everyone in the party took a look. Afterward Keeler spent some time studying Saturn more carefully, which led to Lick Observatory's first discovery. He spied a fine, dark line in Saturn's outer ring, “a mere spider's thread,” as he described it. It was a breach (now best known for historic reasons as the Encke Gap, after an early-nineteenth-century German astronomer) that had never before been clearly seen. A superb drawing Keeler made of Saturn, based on his sketch of the planet that night, was displayed at the 1893 Chicago World's Fair.

James Keeler

(Mary Lea Shane Archives of the Lick Observatory, University

Library, University of California-Santa Cruz)

Six feet tall with fair wavy hair, Keeler cut a fine figure. Despite his isolated upbringing in rural Florida, he became a keen judge of human nature and was often called upon to handle personnel and scientific crises at the observatory, which he carried out with the calm discretion of an international diplomat. “He was tolerant, amused and unwilling to take sides,” said Keeler's biographer Donald Osterbrock. “He always sought to put the best construction he could on anyone's activities, to emphasize the positive, and never to criticize unless absolutely necessary. It was perhaps not the most courageous philosophy in the world, but it [took] him far.”

And as an astronomer, Keeler was outstanding, studying a range of subjects from solar eclipses to planetary features. Photography was still in its infancy, so Keeler continued to make drawings that were praised by his colleagues as marvelous reproductions. “Beautiful and accurate,” reported fellow Lick astronomer Edward E. Barnard in a notice to the Royal Astronomical Society. “… [Keeler] has a real artistic ability such as very few observers possess.” Keeler's real forte, however, was in using a spectroscope, which was a relatively recent addition to astronomy's instrumental arsenal. The scientific basis for it was established in the seventeenth century.

A young Isaac Newton, sitting in a darkened room in 1666, let a small stream of sunlight enter through a hole in his window shutter. He then passed it through a triangular prism of glass. Beholding a rainbow of colors on the wall behind him, an enchanting phenomenon observed with pieces of glass since antiquity, Newton clearly demonstrated that white light was a mixture of many hues: On one end was a band of red, followed by orange, yellow, green, and blue, until it reached a deep violet on the other end. He dubbed this multicolored display a spectrum, a word previously used to denote an apparition or phantom. By the early nineteenth century Joseph von Fraunhofer, a master Bavarian optician, cleverly combined a slit, a prism, and a small telescope—what came to be called a spectroscope—to examine the spectrum of the Sun more closely. Peering through the eyepiece, he was surprised to discern hundreds of dark lines in the spectrum, as if a series of black threads had been sewn across a rainbow. They resembled the ubiquitous bar codes now found on consumer products. But unfortunately, Fraunhofer died before he could pursue the origin of those mysterious dark slashes.

Answers arrived from the creative experiments being conducted in chemistry laboratories. Even before Fraunhofer's spectral tests, chemists had noticed that metals or salts, when heated to incandescence, emit certain colors. Salts containing sodium, for example, burn an intense yellow-orange when heated by a hot flame. When looking at the heated material through a spectroscope, the chemists saw that its spectrum was composed of discrete lines of color, resembling a picket fence with colorful posts. Whereas the solar spectrum was a continuous rainbow riddled with dark lines, these laboratory spectra were the exact opposite: thin bright lines of colorful emissions set against a dark background.

By 1859 the physicist Gustav Kirchhoff and the chemist Robert Bunsen (creator of the legendary