The tech mechanism used by James Webb astronomers to ‘color’ telescope photos

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The spectacular images that the James Webb Space Telescope has left us since last July 12 show nebulae, galaxies and even an exoplanet never before photographed. These heavenly bodies have come to us colored, but its images reach Earth in black and white, since the Webb is only capable of capturing infrared light.

But the team webb who work with these images, how do you choose the colors with which each figure is painted in the photographs? For it, assign various infrared wavelengths to the colors of the visible spectrum that determine which ones resemble what the human being sees red, blue, yellow, green, etc.

It should be noted that the color of the images is not what the telescope observes, but it is an approximation. “Something I’ve been trying to change about is people’s opinion, which stop obsessing over the idea of ​​’is this what it would look like if I could go on a spaceship and look at it in person?’“, pointed for Gizmodo a data imaging developer at the Space Telescope Science Institute, Joe DePasquale.

The mission will take place in December aboard the Crew Dragon spacecraft.

The expert gave the example of the covid-19 illustrations: “You don’t ask a biologist if you can somehow reduce yourself to the size of a cell and observe the coronavirus.”

The Webb observes space using infrared systems because many interesting space objects shine brightly in ultraviolet light, X-rays, or radio waves imperceptible to humans. The technology who uses the telescope allows you to see infrared light, which has a longer wavelength than red visible lightbut shorter than microwaves.

At left is a monochrome image of the South Ring Nebula with infrared data from Webb.  On the right the same 'coloured' image
At left is a monochrome image of the South Ring Nebula with infrared data from Webb. On the right the same ‘coloured’ image

“These are instruments that we have designed to extend the power of our vision, and go beyond what our eyes are not able to perceive because they are not sensitive,” DePasquale explained. I’m trying to bring out the most detail and the richest color and complexity found in the data without actually changing anything.

Webb’s observations are loaded with a wealth of information important to researchers, which is then translated into color for society to see. In addition to coloring them, the researchers Photographs of cosmic rays and reflections of bright stars should be cleanedfor instance.

DePasquale comments that some people think that when a spatial image is ‘colored’, the colors are chosen “arbitrarily to create a color image”. Experts like him prefer to use the term ‘representative color’ because he believes that “it perfectly encompasses the work we do of translating light to create a true color image, but in a range of wavelengths that our eyes are not sensitive to.” .

Longer infrared waves are usually assigned redder colors and shorter ones bluer colors. Alyssa Pagan, science imaging developer at the Space Telescope Science Institute, notes that they have filters on the instruments “that collect certain wavelengths of light, to which we then apply a color that is closer to what we think it would be. in the visible spectrum.

In addition to the wavelength, professionals also look at the elements they contain, as oxygen, ionized hydrogen or sulfur.

The space telescope has four instruments to detect all of these features: a near-infrared camera (NIRCam), a near-infrared spectrograph, a mid-infrared instrument (MIRI), and a guidance sensor and spectrograph.

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