NOVA | PBS | 2023 Feb 21
Over the past year, we’ve seen some of the most spectacular images of space yet, courtesy of the new James Webb Space Telescope (JWST). But JWST only observes infrared light, which has wavelengths longer than the human eye can see. So how do NASA’s data image developers turn those observations into colorful, awe-inspiring images? The trick is in “chromatic ordering,” shifting those wavelengths down the spectrum, just as a musician might play a piece of music in a different key. That means keeping the differences between the wavelengths consistent but moving them into the part of the electromagnetic spectrum that we can see.Image Credit: X-ray: NASA/CXC/Penn State Univ./L. Townsley et al.;
IR: NASA/ESA/CSA/STScI/JWST ERO Production Team
When that transfer is complete and the images combined, the result is a style that visuals developers like Joe DePasquale of the Space Telescope Science Institute call “representative color”: an image that is aesthetically pleasing and also essentially a data visualization. One reason JWST records particular wavelengths of light is because they can indicate the presence of specific elements. Because these images are created using chromatic ordering, it’s possible to “read” them a bit like a map: a red area is rich in hydrogen or sulfur, while blue contains oxygen.
Some shades might look muddy next to one another or create an image that’s too bright, almost lurid, so DePasquale might make an adjustment, or raise the contrast to make the colors pop. Still, in every stage of the process, “we’re always respecting the data,” he told NOVA. “We're not trying to introduce things that weren't there in the data to begin with, and we're not trying to remove things that are there.” ...
NOVA: New Eye on the Universe airs tonight (2023/02/22) on PBS.