![]() “Thank heavens they did because it was not something that just immediately popped out, what this spectral classification system was.” “It’s almost incomprehensible that this was all done visually by examining the plates under magnifying glasses,” said Josh Grindlay, an astronomer at Harvard. The first major developments to come out of the Harvard plate collection were systems that classified stars based on the tiny white lines slicing the spectrum’s grey rainbow. In the early days of the collection, these spectra were the cutting edge of astronomy. But about one in five is a spectrographic plate, with each star depicted as a grey smear (representing the rainbow of visible light) perhaps a quarter inch long. Today, these plates draw the most interest from scientists. The majority are photographic: clear glass sheets scattered with dark specks of stars. ![]() “He also realized that what astronomy needed was collecting data on a massive scale.” “Pickering realized that he should be recording the whole sky photographically in both hemispheres, and that had never been done before,” said John Hearnshaw, an astronomer and historian at the University of Canterbury in New Zealand. It was begun under the leadership of observatory director Edward Pickering, who also made a point of hiring talented female mathematicians and astronomers. There were-and still are-other collections of astronomical plates, but Harvard’s is far and away the largest, and unlike many, it covers both the northern and southern skies. “I don’t think anybody has ever made a list of what the discoveries were from the plate stacks because they were used in a lot of other ways,” said Owen Gingerich, an astronomer and historian of science at Harvard. Astronomers are still using the collection, and even finding new ways to keep it scientifically useful. The book ends around World War II, but the collection certainly doesn’t, with plates made until 1989. The story of the people behind the plates is told beautifully in Dava Sobel’s new book The Glass Universe. ![]() The Harvard College Observatory’s collection contains more than half a million images of the stars chemically stamped onto glass rectangles, the oldest created during the 1880s. One particular collection of astronomical images has fed the minds and calculations of scientists making some of the most important discoveries of their times. The same is true of photographs of the stars. We love photographs for the way they capture a moment, a smile, a friendship - although sometimes we don’t realize the camera’s luck for years.
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