Webb's First Images Were Also a Lesson in How Scientific Pictures Are Made
The first full-colour image from the James Webb Space Telescope was unveiled on 11 July 2022. The wider set of images and spectroscopic data followed on 12 July. Together, they introduced the public to an observatory's capabilities. They also offered a lesson in reading pictures that show light our eyes cannot directly see.
Several observations, not one universal view
NASA's initial release included the galaxy cluster SMACS 0723, the Carina Nebula, the Southern Ring Nebula, Stephan's Quintet and data from the exoplanet WASP-96 b. The range of targets was part of the point: different instruments and kinds of observation could answer different questions. Webb is a partnership between NASA, ESA and the Canadian Space Agency.
NASA, ESA, CSA, and STScI — ESA/Webb. Official image · CC BY 4.0
NASA, ESA, CSA, and STScI — ESA/Webb. Official image · CC BY 4.0
NASA, ESA, CSA, STScI, and the Webb ERO Production Team — ESA/Webb. Official image · CC BY 4.0
NASA, ESA, CSA, and STScI — ESA/Webb. Official image · CC BY 4.0
It is worth pausing over the inclusion of a spectrum beside the pictures. A spectrum separates light into information that can be investigated rather than presenting a scene in the familiar form of a photograph. Giving it equal attention helps prevent the most immediately dramatic image from becoming the whole story.
Colour as a way of showing measurements
NASA's explanation of Webb image processing describes how infrared observations are translated into visible colours. Separate exposures through different filters can be combined, with colours assigned to represent wavelength ranges. The result is not the view a human eye would necessarily see from a spacecraft window.
NASA, ESA, CSA, STScI, Webb ERO Production Team — ESA/Webb. Official image · CC BY 4.0
NASA, ESA, CSA, and STScI — ESA/Webb. Official image · CC BY 4.0
NASA, ESA, CSA, STScI, and the Webb ERO Production Team — ESA/Webb. Official image · CC BY 4.0
NASA, ESA, CSA, STScI, and the Webb ERO Production Team — ESA/Webb. Official image · CC BY 4.0
NASA, ESA, CSA, and STScI — ESA/Webb. Official image · CC BY 4.0
That does not make the image arbitrary. The colour treatment is connected to data and to decisions about which structures should become legible. A useful caption can explain those choices, allowing a viewer to distinguish an observation from its presentation without treating either as disposable.
This is a familiar problem in another form for anyone working with maps, diagrams or visual archives. A representation selects and organises information. Its integrity depends less on appearing untouched than on making its relationship to the underlying material clear. For Webb, the filter information is part of that relationship.
A record held at a particular moment
NASA described the first deep field as its deepest and sharpest infrared view of the distant universe at the time of release. That historical statement should not be silently converted into a claim about the oldest galaxy known today. The first-image collection and later research results are different subjects.
NASA, ESA, CSA, STScI, O. De Marco (Macquarie University), J. DePasquale (STScI) — ESA/Webb. Official image · CC BY 4.0
NASA, ESA, CSA, STScI, O. De Marco (Macquarie University), J. DePasquale (STScI) — ESA/Webb. Official image · CC BY 4.0
Returning to July 2022 is rewarding because it shows scientific communication taking several forms at once: an image, a caption, a spectrum and an explanation of the instruments. The spectacle draws attention, but the supporting information gives that attention somewhere to go. Webb's first images invite us not only to look farther, but to become more careful readers of what a scientific picture can tell us.
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