Are space photos really those colours?
How black-and-white measurements become a colourful view of a nebula.
Space & science | 4-minute read | Sources checked 9 October 2026 (Japan time)
A space image can record real light without showing the colours a human eye would see. In this picture from the James Webb Space Telescope, blue and orange help display observations made in infrared light, beyond our vision. The colours were assigned during image processing. Image data and colour information
Observed image: the Cosmic Cliffs in the star-forming region NGC 3324, in the Carina Nebula. This is a colour composite of near-infrared observations from Webb’s NIRCam, released on 12 July 2022. Credit: NASA, ESA, CSA, STScI. Official image source
The scene invites an earthly reading: mountains beneath a blue sky. Yet that ridge is the edge of a cloud of gas and dust, and its blue surroundings do not represent blue daylight. Even the nickname, Cosmic Cliffs, tempts us to imagine a landscape we could stand in. What the image shows
So where, between arriving light and the finished picture, did those colours appear?
One frame measures one slice of light
Webb’s image data record how much light reaches different places on a detector. Display those measurements in shades of grey, and bright and faint areas become visible.
A filter limits the light reaching the detector to a particular range of wavelengths. Observe the same object through several filters and you get several views, each recording the brightness of a different slice of light. ESA/Webb’s processing explanation
A grey image does not mean that space itself was grey. A bright patch in a frame taken through a red-light filter, for instance, represents a strong signal in red light. The grey used to display the measurement and the light that was measured are different things. How Hubble images get their colours
To make a colour composite, image specialists give the separate frames display colours and align matching stars and other features. Where the frames overlap, their contributions mix.
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Original explanatory diagram. It contains no observed image data and does not reproduce the complete processing of the photograph.
Processing also brings out faint details by adjusting the range of brightness displayed and removes unwanted detector artefacts. Specialists work with scientists as they prepare an image for release. The finished view reflects both the observations and decisions about making their features readable. From data to a finished image
What blue means in this particular picture
The Cosmic Cliffs NIRCam image uses six filters. The frame called F090W is assigned blue, F200W green and F444W red; the other three contribute cyan, yellow and orange. You do not need to memorise those names. The useful point is that the connection between measurements and colours is published. This image’s colour key
A blue area therefore does not simply mean “this would send blue light to my eyes”. You are seeing the combined contributions of infrared frames displayed in chosen colours.
Shorter wavelengths are often assigned bluer colours and longer ones redder colours, but the exact mapping matters. Here, F470N is yellow: a strictly wavelength-ordered rainbow would not explain every assignment. How colour choices are made
Three different things a space image can do
Approximate familiar, visible-light colours. An image can combine observations through red, green and blue filters to represent a natural-looking colour balance. Rosetta’s colour view of comet 67P is an example. Even there, brightness was adjusted to reveal surface detail. Natural colour does not promise the same brightness as an unaided view. Rosetta’s colour-image explanation
Use colour to distinguish selected kinds of light. That includes invisible infrared, as in our Webb example. Visible wavelengths can also receive representative colours to make differences easier to see. A visible-light example Hubble has infrared images too, so the telescope’s name alone cannot tell you whether a picture approximates human vision. A Hubble infrared example
Illustrate a possible appearance or explanation. Captions saying “artist’s impression” or “artist’s concept” identify a different kind of picture. Its details may draw on scientific evidence without having been photographed. An illustration of an unusual explosion between galaxies, for example, explicitly describes the depicted explosion as conjectural. An artist’s concept, labelled as such
These distinctions let you enjoy an image while understanding what it offers. The caption can tell you what light was measured, what the colours represent, and whether you are looking at an observation or an illustration.
Look back at the ridge
The blue area has faint wisps within it. The orange cloud contains darker folds and bright edges. Knowing how the colours were made leaves plenty to explore.
Next time a space picture catches your eye, try a second question alongside “Are those colours real?”: “What are these colours helping me see?” Look for “Color Info” or “Colours & filters” on the image page. The picture usually becomes more interesting with its explanation attached.
Colour is only one way a space image can surprise us. In this Einstein ring around a galaxy, the paths taken by the light create the remarkable shape.
Sources and image credit
The linked sources are primary material from NASA, ESA, ESA/Hubble and ESA/Webb. The photograph was released in 2022; this is an explanation of that image, not a new discovery in 2026.
The official preview is reproduced without local recolouring or added features. Credit: NASA, ESA, CSA, STScI. Used for factual editorial explanation under NASA’s image and media guidelines. No endorsement of this article or any service by NASA or the credited organisations is implied.