The James Webb Space Telescope has provided amazing images of the universe. But what are we looking at, exactly?
It goes without saying, but these are not photographs. These are data visualizations! And that data is the impact of photons – light energy – on highly sensitive circuitry millions of miles away from us. The Webb Telescope’s various sensors measure this energy and send this data back to Earth, where it can be transformed into something that human eyes can see.
This rendering process can make people suspicious of these images – that we don’t see what’s really there, but something artificial or manipulated. The truth is more interesting: like any data set, measurements of light in the universe can be manipulated. But scientists have standards and techniques to ensure their visualizations convey useful information about the world, much like economists try to pinpoint rising inflation.
Turn James Webb Space Telescope data into graphs
For scientists, most of the data of interest will be found in spreadsheets or spectrographs, graphs that show the presence of specific elements as a function of the frequency of light reflected, absorbed, or emitted by an object in space. . Jonathan McDowell, astronomer at the Harvard-Smithsonian Center for Astrophysics, compare visualizations to crime scene photos and spectrograms to DNA analysis – one gives you the lay of the land, but the other offers much more detail.
One of the first five images we saw was actually a spectrograph of the atmosphere of a planet 1,150 light-years from Earth. The new telescope was able to spot the chemical signature of the water:
This is what will guide science: precise measurements of distant things. Thinking about it for a moment, it is absolutely insane to be able to say with certainty that there is water vapor on a planet so far away. Most of Webb’s scientific impact will come from these analyses.
And if that’s what’s important, why do we gawk at images like these?
James Webb Space Telescope images are visualizations of data
It’s a powerful method of communication, says Rob Simmon, a data visualization expert at remote sensing company Planet and formerly at NASA. As his work points space sensors toward Earth, he faces the same challenges as astronomers looking at more distant targets.
“This transformation of numbers into visual, especially a visual that has an immediate impact, is super important,” he says. “Even other astronomers outside of a particular discipline will need this type of bridge.”
On the one hand, images have scientific value. The JWST “deep field” image above may look like a world of stars, but the key context is that thirty years ago we thought there was nothing there. Then, in 1995, the director of the Hubble Space Telescope used his spare time to stare at what was then recorded as an empty patch in the sky. The resulting image showed thousands of galaxies at different ages, definitely upending the idea of an unchanging universe. Now JWST has confirmed that, and more, looking even deeper.
And at another wavelength. Hubble’s sensors were primarily designed to observe the visual spectrum of light: the frequencies that the human eye can see. JWST, however, also captures infrared light that human eyes cannot detect. This is important for astronomers because the universe is expanding, causing light from more distant objects to shift to a longer or “redder” wavelength. JWST can see some of the oldest objects in the universe because it can detect this “red-shifted” light.
Make invisible light visible
To turn them into something we can see, scientists must choose how to represent each frequency that humans cannot see, but rely on the same physical properties that humans know.
“Infrared colors are just as real as visible colors. What we’re doing with Webb isn’t inventing colors,” JWST researcher Klaus Pontoppidan said last week. “We always maintain this order: the color blue means a shorter wavelength, the color red means a longer wavelength… you can see the translation of a language that you don’t understand. If you had infrared eyes, this is what you could see.
Consider two Webb images. This one, based on the telescope’s near-infrared camera, shows new galaxies and stars in the Carina nebulae:
This same part of the sky was also photographed with the telescope’s mid-infrared camera, which better captures clouds of space dust. Here is an image that highlights the data of this instrument:
None of these visualizations are “false” or “false”. What makes them different is what their creators try to communicate. On a clear day, I can see the Golden Gate Bridge from my window, but it’s often obscured by fog. If I had the right infrared camera it could look through the fog and I could produce similar images – of the fog or the bridge behind it. These choices are even more important when you’re shooting something light years away rather than miles away – there’s just more in between.
For scientists, it is the most useful for deepening their understanding. They act as designers, trying to communicate specific results to their audience.
The responsible way to communicate scientific data
“My rule of thumb is that I try to do things that are global to an image,” Simmon says, to avoid presenting a misleading image by selectively changing a small part. This means consistency in color choices. But this can become more difficult, for example, when trying to represent the 3D environment of space in a 2D image: astronomers will make choices about what is in the foreground or background of a picture.
Debates over the veracity of scientific imagery are not new – Simmon points out that cartographers are the primary viewers of remote sensing. Prior to digital technology, the chemistry used to make film presented similar choices to photographers. One brand may have brighter reds, another may have more shadow detail. This is what many Instagram filters try to simulate.
Indeed, in the exploration of the American West, when painters and eventually photographers attempted to capture the otherworldly landscapes of the Grand Canyon, similar questions of veracity arose. Thomas Moran was a painter who worked for popular magazines, his stunning images are credited with inspiring the national parks movement.
William Henry Holmes, on the other hand, was a geologist focused on scientifically recording what he saw. Moran won more fame, but Holmes won the respect of scientists.
Art historian Elizabeth Kessler argues that the visual language of space telescope imagery can be traced to landscape art of this era. It’s worth mentioning that while the glorious images of deep space won’t lead to colonization at the space frontier (until we invent some sort of faster-than-light travel), they do play a propaganda role. promoting the results of government spending to a wider audience. an audience that might not care about spectroscopic analysis but would like to get a sense of its place in the universe.
And while navigating the line between portraying something literally and how it makes you feel can be a gray area, the JWST images recall what author Wallace Stegner wrote about Holmes: “At least once, when there was no reason to improve nature because nature was superlative, once when pure geology was art, he made pictures that no one has made since… art without falsification.