How we see the invisible universe

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How we see the invisible universe

Published: 19 Jun. 2025, 00:05

Audio report: written by reporters, read by AI

Ko Jae-hyun

The author is a professor at the School of Semiconductor and Display Engineering, Hallym University.

When giving public lectures on the science of light, I often present astronomical images — vivid, colorful portraits of distant galaxies and nebulae. A common question follows: “Is the universe really that colorful?”

The short answer is no. While these images may appear visually stunning, much of their color is not what the human eye would actually see. But that doesn’t mean the images are fake. Rather, they are visual translations of information far beyond the visible spectrum.

Spiral galaxy NGC 628, located 32 million light-years away from Earth, is seen in an undated image from the James Webb Space Telescope. NASA, ESA, CSA, STScI, Janice Lee (STScI), Thomas Williams (Oxford), and the PHANGS team. [REUTERS/YONHAP]

Modern telescopes, such as NASA’s James Webb Space Telescope, operate in wavelengths that humans cannot perceive — specifically the infrared. These longer wavelengths capture crucial details about celestial bodies, such as heat signatures and distant starlight that is invisible to optical telescopes.

To render this invisible data comprehensible, astronomers assign visible colors to different wavelengths in a process called "false color imaging." Each segment of infrared data is mapped to a corresponding hue — blue, green, or red — so that the final image is not a literal photograph, but a visual interpretation based on scientific data. What we see is not the "true" color of space, but a way to make sense of the data our eyes were never designed to process.

A case in point is SPHEREx, a space telescope jointly developed by Korea’s Astronomy and Space Science Institute and NASA. Recently launched, it carries a unique spectrometer capable of scanning the universe in 102 different infrared bands. This has led to popular comparisons to color televisions with 102 channels. Yet, the analogy still hinges on data we cannot see directly. The images SPHEREx will produce, like those of James Webb, will also be processed through false-color techniques.

The Crab Nebula, the result of a bright supernova explosion seen by Chinese and other astronomers in the year 1054, 6,500 light-years from Earth, is seen in an image taken by the James Webb Telescope on June 3, 2024. At its center is a neutron star, a super-dense star produced by the supernova. This image shows the X-ray data from Chandra along with infrared data from the Webb space telescope. [REUTERS/YONHAP]

These instruments, whether in orbit or stationed on the ground, expand the narrow range of human perception. Through them, we glimpse a universe filled with light and energy that would otherwise go unnoticed.

So, the next time an astronomical image appears in the news — perhaps showing a glowing nebula or a faint galaxy from billions of years ago — look beyond the colors. Those images are not artistic embellishments but rather tools that help us visualize the invisible. Behind each hue lies a wealth of scientific insight waiting to be interpreted. Let your imagination roam as you take in the rich, coded language of the cosmos.

Translated from the JoongAng Ilbo using generative AI and edited by Korea JoongAng Daily staff.