In the 19th and early 20th centuries, astronomers cataloged the universe on photographic glass plates.
Astronomers still study these plates, which serve as a record of the sky spanning nearly 100 years.
Compared to the faint objects printed on the plates, the James Webb Space Telescope images show notable improvements in telescope technology.
Today, humanity’s most advanced telescopes allow astronomers to peer far into the universe. NASA’s newest and most powerful astronomical workhorse, the James Webb Space Telescope, has been providing sharp images of the most distant objects in the universe since July.
Long before astronomers developed cutting-edge technology for telescopes like Webb, they cataloged the universe using an early form of photography on glass plates.
For nearly 100 years, beginning in the late 19th century and into the 1980s, astronomers used photographic glass plates as thick as window panes to capture light from stars, clusters and other celestial objects. To map the sky, they meticulously hand-placed a telescope on an object over a long period of time. Exposures were made on glass plates coated with photosensitive emulsions, with astronomers later developing the plates as a film in a darkroom.
Astronomers meticulously studied these clear glass plates, which were negative, littered with dark specks of stars and other cosmic objects.
The resulting plates – the first photographic atlases of the sky – allowed astronomers to establish a classification system for stellar objects, which ultimately served as a record of the sky for nearly a century.
Astronomers are still using these transparent plates, as they provide information about the stellar past and the evolution of our universe. Compared to Webb’s infrared images, photographic plates of the same parts of the night sky show how technological developments have led to clearer and deeper views of the cosmos.
“We have gone from the human eye, to photographic plates and now to electronic devices, in the case of the James Webb Space Telescope,” Giovanna Giardino, a Webb scientist at the European Space Agency, told Insider. “Technological leaps have allowed us to have larger telescopes, which can see fainter objects,” added Giardino.
Compared side by side, images of the same cosmic objects taken on old-fashioned photographic plates and by Webb show just how advanced our ability to capture and study the cosmos is.
The Carina Nebula, a cluster of gas and young stars, 7,600 light-years away and four times the size of the Orion Nebula, was first discovered in 1752. It is a vast star-forming region and home to extremely massive young stars. including Eta Carinae, a volatile system containing two massive stars that closely orbit each other.
The Harvard College Observatory has a collection of over half a million sheets of glass, including one taken in Arequipa, Peru, in 1896, using a 24-inch telescope that faintly captured the nebula against a larger portion of the sky.
In July, Webb also captured an image of the Carina Nebula, but there is a noticeable difference in scale between the two images. Nico Carver, a librarian at Harvard College Observatory, told Insider that Webb’s magnification is 100 times better than what astronomers could capture in photographic glass plates.
“Webb is a marvel of technology. It’s a very advanced instrumentation,” Giardino said, adding that Webb’s skill was made possible by advances in telescope technology over time. “Science is always based on what we know,” Giardino said.
Galileo Galilei made the first detailed observations of the planet in 1610 with a small telescope.
The first images of the gas giant show, top left, show faint bands of clouds and the Great Red Spot, a huge storm that has been whirling for centuries. The glass plate image was taken in 1889 in Wilson’s Peak, Nevada, using a 13-inch telescope, according to Carver.
Recent images by Webb, captured in July and released in August, show the planet’s turbulent atmosphere and the Great Red Spot in stunning detail. The telescope also identified Jupiter’s thin rings, made of debris dust particles, and the auroras visible at Jupiter’s north and south poles.
The image of Jupiter on a glass plate, top left, is from the Carnegie Institute, which houses a collection of 250,000 glass plates taken from the Las Campanas Observatory in Chile and the Mount Wilson and Palomar observatories in Calfornia.
Stephan’s Quintet, a collection of five galaxies 290 million light-years from Earth in the constellation Pegasus, was first discovered in 1877. Four of the five galaxies gravitationally interact in a slow-motion merger. The fifth galaxy is much closer to Earth, about 40 million light years away.
The fifth is faintly visible in the image of the glass plate taken in 1974, top left. On July 12, when Webb released the first batch of images, one of him captured Stephan’s Quintet in unprecedented detail.
According to Giardino, one of the main reasons Webb can take such sharp photos of the group of galaxies is its ability to detect infrared light. Webb’s image is a huge mosaic of nearly 1,000 images, according to NASA, containing more than 150 million pixels.
A higher number of pixels allows astronomers to capture high-resolution views of the cosmos, according to Giardino. “This was a huge improvement,” he said.
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