- In the 19th and early 20th centuries, astronomers cataloged the universe on glass photographic plates.
- Astronomers still study these plates, which have served as a record of the sky for nearly 100 years.
- Compared to faint objects stamped on plates, images from the James Webb Space Telescope show dramatic improvements in telescope technology.
Today, humanity’s most advanced telescopes allow astronomers to peer into the universe. NASA’s newest and most powerful astronomical workhorse, the James Webb Space Telescope, has been delivering sharp images of the most distant objects in the universe since July.
Long before astronomers developed state-of-the-art telescopes like Webb, they cataloged the universe using an early form of glass-plate photography.
For nearly 100 years, from the late 19th century to the 1980s, astronomers used windowpane-thin glass photographic plates to capture light from stars, clusters, and other celestial objects. To map the sky, they painstakingly placed a telescope on an object by hand over a long period of time. The exposures were made on glass plates coated with photosensitive emulsions, and the astronomers then developed the plates as a film in a dark room.
Astronomers meticulously studied these clear glass slides, which were negatives dotted with dark spots from 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 still use these transparent plates as they provide information about the stellar past and the evolution of our universe. Compared to Webb’s infrared images, the photographic plates of the same parts of the night sky show how technological advances led to clearer and deeper views of the cosmos.
“We’ve 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,” Giardino added.
Compared side by side, images of the same cosmic objects taken on old photographic plates and by Webb show how far our ability to capture and study the cosmos has advanced.
The Carina Nebula, a collection of gas and young stars, 7,600 light-years away and four times larger than the Orion Nebula, was first discovered in 1752. It is a vast star-forming region and home to young stars extremely massive. including Eta Carinae, a volatile system containing two massive stars that orbit each other very closely.
Harvard University Observatory has a collection of more than half a million glass plates, 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 dramatic scale difference between the two images. Nico Carver, a librarian at Harvard University Observatory, told Insider that Webb’s magnification ability is 100 times better than what astronomers could capture on photographic glass plates.
“Webb is a marvel of technology. It’s very advanced instrumentation,” Giardino said, adding that Webb’s ability 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, above left, faint bands of clouds and the Great Red Spot, a huge storm that has been spinning for centuries. The glass plate image was taken in 1889 at Wilson’s Peak, Nevada, using a 13-inch telescope, according to Carver.
Recent Webb images, captured in July and released in August, show the planet’s turbulent atmosphere and the Great Red Spot in remarkable detail. The telescope also detected Jupiter’s thin rings, made of dust particles from the debris, and auroras visible at Jupiter’s north and south poles.
The glass plate image of Jupiter, above left, is from the Carnegie Institution, which maintains a collection of 250,000 glass plates taken from the Las Campanas Observatory in Chile and the Mount Wilson and Palomar observatories in California.
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 are gravitationally interacting in a slow-motion merger. The fifth galaxy is much closer to Earth, about 40 million light-years away.
The quintet is barely visible in the glass plate image taken in 1974, top left. On July 12, when Webb released the first batch of images of him, one captured Stephan’s Quintet in unprecedented detail.
According to Giardino, one of the main reasons Webb is able to take such sharp images of the galaxy group is because of 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.
More pixels allow astronomers to capture higher resolution views of the cosmos, according to Giardino. “This was a huge improvement,” he said.