Palomar Observatory (Part 3)

You may want to start with the earlier posts on our trip to Palomar Observatory: Part 1 and Part 2.

Longtime readers of Lofty Ambitions know that we’ve devoted a number of blog posts to the Manhattan Project and its legacy. We’ve made several treks to Los Alamos. We visited and wrote about the Nevada Test Site, that enormous expanse of the American west where the government tested, both above- and below-ground, several generations of the nuclear weapons designed at Los Alamos National Lab. We each have writing projects—Doug a novel and Anna a memoir—that involve the Manhattan

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Project and America’s legacy of atomic energy, nuclear weapons, and our irradiated environment. That was a project often labeled Big Science.

Defining Big Science has long been a loose, intuitive, “I know it when I see it” endeavor. Roughly, it denotes a project so large in scope and aims that it requires collaboration between universities, government, and industry. The Manhattan Project is the prototypical Big Science project, and it is sometimes referenced as the tipping point between the era when science was an individual or small-team practice and the more large-scale, industrialized practice that exists today. In the book, The Manhattan Project: Big Science and the Atom Bomb, author Jeff Hughes devotes a chapter (Chapter 2: “Long Before the Bomb”) to the origins of Big Science. In his explanation, he mentions the role of astronomy and observatories in the creation of this phenomenon. Palomar Observatory, then, and particularly its the 200-inch Hale Telescope fit squarely into the tradition of Big Science.

Model of Hale Telescope inside the Dome
Model of Hale Telescope inside the Dome

The initial idea for what would become the Hale Telescope was put forward in a Harper’s magazine article by George Ellery Hale in 1928. Later that year, the Rockefeller Foundation gave Hale a $6M grant—the largest scientific grant that had ever been awarded at that time—to begin construction of the telescope. It would be twenty years before the project was completed—twice as long as the construction phase of an earlier Hale telescope, the 100-inch at Mount Wilson Observatory—and Hale wouldn’t live to see the project through, dying at the halfway point in 1938. His colossal masterpiece would, however, be named in his honor.

In earlier posts, we recounted some of the outsized numbers associated with this project. The one that matters most, however, is 200—the 200-inch mirror. In doubling the mirror’s diameter over the previous largest telescope, Hale’s new telescope had four (4x) times the surface area, and in telescopes, surface area determines how much light you can gather. The more light, the farther the telescope can see and the smaller the objects that it can resolve.

Constructing the telescope’s primary mirror was a gargantuan project of its own. Hale first worked with General Electric in an attempt to build the mirror out of fused quartz. As our docent on the Palomar tour pointed out, “The only thing Hale learned was GE didn’t know how to do it.” Reports vary, but Hale spent at least $600K—10% of his grant—on this failed effort.

Hale Telescope
Hale Telescope

The backup plan involved working with Corning Glass and their newly developed Pyrex glass (developed in 1915), a low thermal expansion glass. For telescopes, it’s extremely important that flexing and expansion due to temperature change is minimized so that the mirror maintains its shape. Corning’s first attempt at pouring the 200-inch mirror ended in failure when some of the mounting brackets melted in the heat. Despite the fact that that mirror would never be usable, it was used to develop engineering models of cooling. In a testament to the dictum “there’s a sucker born every minute” (oft attribued to PT Barnum, but likely said by someone else), Corning Glass put the failed mirror on display and charged to see it. In now resides in the Corning Museum of Glass, and the company has a lovely website dedicated to the mirror’s development.

The engineering and development of a useable mirror required pouring several test “blanks” for working out the process. It’s interesting to note that one test mirror, itself a not-insignificant 120 inches in diameter, would later become the primary mirror for the Lick Observatory’s C. Donald Shane telescope. When it began operation in 1959—astronomer’s call such an event First Light—the Shane 120-inch telescope was the second largest in the world, behind the Hale Telescope.

Distant Planets (NASA/JPL-Caltech/Palomar Observatory )
Distant Planets (NASA/JPL-Caltech/Palomar Observatory)

The supporting structure and mount developed for the big Hale mirror are also enormous. Engineered by Westinghouse and manufactured in its South Philadelphia factory, the steel beams, tubes, and gearing required to support and aim the telescope weigh in at 530 tons.

Since its First Light in 1949, Hale has been in operation roughly 300 nights every year. Over the history of those long nights, the Hale Telescope has dramatically increased our understanding of the universe. An important part of this work was the discovery of  “quasi-stellar objects,” more popularly known as quasars. Initially discovered through radio astronomy, the light spectra of quasars defied characterization until astronomers Alan Sandage and Maarten Schmidt used the Hale Telescope to identify 3C 273, an astronomical object that had previously been described only as a radio source.

The funding, constructing, and operation of Palomar Observatory’s Hale Telescope tracks the evolution through the 20th century of astronomy into Big Science. For a large portion of the 20th century (1948-1976), the Hale Telescope was the largest optical telescope in the world. It remains the largest one we’ve seen in person.

Keep reading with PART 4.


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