by NASA on James Webb Space Telescope (JWST) we know how to capture our Universe with unprecedented precision and sensitivity. His images are not only scientifically useful but also beautiful. From blue and gold the The Southern Ring Nebula to pink, orange and purple Cassiopeia AJWST images leave the globe in stunning color.
The images are so amazing, you might wonder, — do these cosmic objects really look that beautiful? What would they look like if we could see them with our own eyes, instead of seeing them through a telescope?
“The fastest answer is, we don’t know,” said Alyssa Pagan, a physics developer at the Space Telescope Science Institute (STScI) and part of the team that works to colorize the JWST images. But one thing is certain: You wouldn’t see the universe like this.
JWST is an infrared telescope, meaning it looks at the universe in wavelengths of light longer than red light, which is the longest wavelength we can detect with our eyes.
Related: How the James Webb Space Telescope’s infrared detectors will open new vistas in astronomy
If you could look directly at these objects, you might see something closer to images from telescopes that rely on visible light, such as the Hubble Space Telescope, said Pagan. But that comparison is not even fair, since Hubble is much larger and more sensitive than the human eye. Also, visible light telescopes may capture different aspects of an image than infrared telescopes, even when aimed at the same target.
So how are the colors chosen for these amazing images, then? JWST targets are observed through several filters attached to the telescope, which “see” in a certain range of infrared light wavelengths. JWST’s Near Infrared Camera, the telescope’s main camera, has six filters, all of which capture slightly different images. Combining these images into a composite allows Pagan and Joe DePasquale, another physics developer at STScI for JWST, to create the full-color images.
When Pagan and DePasquale first receive the images, they appear in black and white. The colors are added to the image later, as the data from the various filters is transferred to the visible light spectrum, Paganách explained. The longest visible wavelengths are red, and the shortest wavelengths are blue or purple.
“We’re using that relationship with wavelengths and color of light, and we’re applying that to the infrared,” Pagan said.
Once all colors have been added to the image, it may go through several additional changes. Sometimes, the original colors can make an image look faded or dusty, and the colors are made more vivid to give it a sharper quality. The colors could also be shifted to emphasize certain features that are not difficult to find.
Pagan and DePasquale also work with researchers to ensure the images are scientifically accurate, especially if they are presented alongside a specific scientific finding, Pagan said. Although the color images do not provide specific scientific data, they can help illustrate certain results.
Sometimes they can also help scientists see areas they want to research, Pagan said. For example, the most distant objects i JWST’s first deep-field view — which appear to appear red because the light traveling so far was stretched out — presented targets for research into the early universe when such objects would exist as they were in the deep field image.
The colors in the JWST images may not be “real,” but don’t get the wrong idea—the colors aren’t meant to trick you, and they’re not chosen to look good. The images are intended to convey as clearly as possible what JWST can see – and what our eyes cannot.
“We’re just trying to improve things to make it more scientifically digestible and also attractive,” Págan said.
You can see some of the differences between images from visible-light and infrared telescopes by comparing images of the iconic Pillars of Creation taken by JWST and Hubble. While large parts of the pillars appear dark red in the Hubble image, the JWST image shows most of the formation in golden and orange tones. This means that the visible light emitted by the longer wavelength pillars (red) is slightly closer to the center of the infrared light spectrum shown in the image.
Much of the hazy material surrounding the pillars in the Hubble image, and even some of the material of the pillars themselves, is also absent from the JWST image, meaning that this part of the gas and dust is transparent in infrared. The JWST image also highlights more areas of star formation in red, which are obscured by thick clouds of gas and dust in the Hubble image.
