At the height of summer, the American space agency (NASA) published the first images from its James Webb space telescope. The whole world was then moved by the beauty of these shots. But these dazzling colors should not be taken for a realistic vision of the universe.
The James Webb telescope has the particularity of making its observations on infrared wavelengths, invisible to the human eye. To go from Webb’s data to images published by NASA, the Space Telescope Science Institute (STSI) plays a key intermediary role.
It is up to this institution to choose the tints and shades of color that will illuminate the shots of James Webb. It transforms the data transmitted by the telescope into an image, clearly visible and understandable by all. A titanic work straddling scientific rigor and artistic freedom.
Scientific and artistic work
When receiving new data, Alyssa Pagan, one of the STSI scientists uses what is called “chromatic order” Where “the Hubble palette” to colorize these images. In other words, it will analyze the wavelengths received by James Webb to transform them into color.
The shorter the wavelengths, the more it will use colors with short wavelengths, generally blue or green. At the opposite extreme, if James Webb’s infrared wavelengths are very long, this will result in an image closer to red or orange, colors with a longer wavelength.
The analysis of these wavelengths also makes it possible to know the composition of the matter in the zone studied by James Webb. Thus a zone of the image which would take on orange hues would be filled with hydrogen. If, on the contrary, the image is “blood” red, it is undoubtedly sulphur.
This color “palette” was first popularized by the Hubble Space Telescope from which it takes its name. It has since been taken over to analyze data from James Webb. By knowing this palette, we can understand the composition of matter at a glance.
Colors are not randomly selected
In the example below, the Carina Nebula, one of James Webb’s earliest photographs, it is possible to see a red band across the bottom of the image. This area is rich in sulfur while the heart of the photo, lighter, is charged with hydrogen. The top of the image is much darker, showing the absence of gas in this area of the sky.
Once this “first layer” has been completed, Alyssa Pagan can let her creativity speak and make the image more “magical”. The scientist then tries to force the contrasts a little or do a little cleaning in the very populated areas. The aim is to make the result easier to understand for the general public, as scientists use the raw data to do their research.
James Webb’s images are not space
Images from Hubble or James Webb are therefore not “photos” of space but rather interpretations. The reality is surely quite different and these shots remain “artist’s views”. Above all, NASA images provide an idea of “life” in the universe, the movement of matter and its evolution over time.
With a bit of poetry, Pagan tries to make space accessible to everyone, by putting color where our eye sees nothing. A job that requires a certain rigor so as not to deceive the general public, but also a lot of creativity to make the images more beautiful than the others.