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“Pretty Pictures”: The Use of False Color in Images of Deep Space

Published onOct 29, 2013
“Pretty Pictures”: The Use of False Color in Images of Deep Space

“Scientific pictures are not decoration but knowledge,” declared photo historian Vicki Goldberg in the first sentence of a 2001 New York Times article on the use of imagery in scientific practice.1 In this statement, we see a prevailing logic at work: the division between subjectivity and objectivity, form and function, pleasure and utility. To decorate, we find, is to augment reality through artifice, to overlay inoperable aesthetic considerations atop what we know to be “true” and factual. It is amid such binary oppositions that the confusion over “false color” emerges in the interpretation of telescopic images of deep space, the most famous of which are images like the Eagle Nebula produced by the Hubble Telescope.2 “False color” is the term used to describe the color assigned to the invisible wavelengths picked up by the telescope’s detectors, including radio waves, infrared light, X-rays, and gamma rays.3 The process of applying color to what were originally black and white images is the source of some contention among audiences who feel “tricked” upon discovering the photographs are not the same as one would “see” in space.4 Indeed, these are cosmic scenes that exist in what Benjamin called “the optical unconscious,” those visual fields to which the naked eye is forever blind, and their authenticity asks to be taken on faith. As NASA image processor Zolt Levay has written in Sky and Telescope:

 The flat-out gorgeous Hubble spacescapes look too good to be true. Are these objects really so colorful? If we could fly out to these celestial wonders, would they look this way to our eyes? If not, as a few hard-core NASA cynics claim, are the pictures being overly colorized to seduce the public? What is ‘truth’ when it comes to Hubble’s universe?5

Figure 1. ‘Gas Pillars in the Eagle Nebula (M16): Pillars of Creation in a Star-Forming Region,’ NASA, ESA,STSsl, J. Hester and P. Scowen (Arizona State University)

In different contexts, images of deep space have functioned to convey an assortment of aesthetic, spiritual, cultural, and scientific narratives: the beauty of inchoate form, the humbling majesty of the cosmos, the endurance of the American frontier, and the depth and necessity of scientific knowledge and investigation.6 The deception implied by “false color” appears to deflate the weight of these various meanings; at stake is the legitimacy and authenticity of those distant nebulae freighted with the dreams of American wonder, exploration and dominance.7 With human vision forfeited as the benchmark of truth, audiences are left to wonder: how much artifice is actually involved in these visual reconstructions?

The doubt surrounding these false-color astronomic pictures reveals much about our ingrained beliefs about the nature of knowledge and how it can be most reliably attained and distributed. Although a longer intellectual history of the suspicion of images, beginning with the Greeks, is too dense to unravel here, it suffices to say that the treatment of these deep space pictures aligns with a certain persistent philosophical anxiety about the relationship between representations and reality. Haunting this outlook is a Platonic distrust of the corrupted copy, the flickering shadows on the darkened cave equated with the impoverished knowledge of the senses. This skepticism can later be traced in Descartes’ rational repudiation of the body, tied to Enlightenment beliefs about the power of reason and the necessity of precise observation and replication of the natural world, in which the disembodied eye is conscripted as an emissary of the intellect. In this paper, I explore how certain dichotomies extending from this epistemological stance, roughly laid out below, are reinforced and maintained in the rhetoric surrounding the images’ production and public dissemination.

Objective                                       Subjective

Intellect                                         Senses

Machine                                        Human

Function                                        Form

Specialist                                       Public

Production                                    Consumption

Scientific Visualization              Art Image

At once documents of both nature and ideology, these deep space images are subject to what historians of science Lorraine Daston and Peter Galison have called “epistemic virtue,” defined as the “norms that are internalized and enforced by appeal to ethical values, as well as to pragmatic efficacy in securing knowledge.”8 In an age in which belief in a utopian science is increasingly ambiguous and the tools for visual manipulation widely distributed, the false color debate appears to expose a fraudulent and morally bereft “science” that, far from releasing “true” representations of natural phenomenon, simply produces for public consumption what are referred to by astronomers as “pretty pictures.” In their colorful appeal to the senses, these images become not “scientific pictures” but decorative, artificial, visually pleasing—in other words, objects of art.

Early Astronomical Images and Mechanical Objectivity

Observational astronomy, as its name clearly implies, has been especially based upon the act of seeing. In fact, the history of astronomy has thus been commonly narrated through the technologically determined progression of better and increased vision, from the pre-telescopic period of the “naked eye” to the digital age of charge-coupled device-powered sight. I begin my discussion with the period called the second era of the telescope, dating from the mid-nineteenth to the mid-twentieth centuries, in which the combination of the telescope with spectroscopy and photography allowed for the production and circulation of new kinds of astronomical images.9 Through the entwined technologies of the camera and telescope, a new prosthetic vision—the mechanical eye—emerged to permanently fix and deliver cosmological phenomena to the public. The resulting images were explained through the emergent idea of mechanical objectivity, a pathway to knowledge that could not be tainted by individual intercession. Here, the photograph’s cultural distinction as a document of unerring truth served an astronomical science in need of the faithful recording and reproduction of natural phenomena for public audiences. Disavowing the unreliable subjectivity of the human hand, the images negated the ideal form in favor of exact imitation. The contemporary controversy over “false color” thus arises as a response to the idea of objectivity that has its roots both in the practice of science and in photography’s very beginnings.10

In his article, ‘Stars Should Henceforth Register Themselves’: Astrophotography at the Early Lick Observatory, Alex Pang describes how astronomers and engravers in California negotiated and regulated the role of “artisanal skill” in the reproduction of astronomical images between 1887-1894.11 Few robust studies have analyzed the creation and public circulation of astronomical imagery, and I use Pang’s thoughtful analysis to begin to sketch out a rudimentary genealogy of how this discourse has taken shape. Then, as now, the creation of the images involved multiple acts of mechanical translation between the media of telescopy, photography, and lithography to achieve an aesthetic of neutrality. Each phase in the process of reproduction introduced the threatening possibility of “error” and manipulation. In this process, the margin between scientific objectivity and aesthetic subjectivity was semantically policed through the notions of “improvement” versus “alteration.” The professional division of labor, and their associated claims to authorship and expertise, reified the boundaries between “art” and “science.”

And yet as much as the interpretive desire was held at bay, the treatment of these images in trade journals and observatory-produced publications was also subject to the demands of its audiences, both lay-people and experts alike. As Pang writes, “the balance between brilliance, contrast, sharpness, flatness and other qualities was not fixed: it could be affected by the objectives of the publisher, the audience, the uses to which a picture would be put, even where it would be read.”12 In their need for arresting imagery that also adhered to professional standards, astronomers and engravers were embroiled in a complex negotiation to create something that read as “real.” Anxieties about the image’s potential to deceive can be seen in the stringent rules for its manipulation. Take, for example, the prescribed treatment for the sky:

A sky that was not perfectly dark, that was mottled or spotted or uneven in tone, could be altered by whatever methods the engraver deemed appropriate, including making alterations in the plate by hand. As long as the interventions were confined to the sky they were acceptable, and counted as corrections rather than dangerous alterations.13

In an image of the Orion nebula, Lick Observatory director Wallace Campbell and astronomer Charles Perrine were enraged to see that engravers took the liberty of darkening the outline of the stars in order to make them stand out. This act of manipulation—or, more inflammatorily, “doctoring”—violated the aesthetic code that worked to maintain the illusion of objectivity. We can imagine that, particularly for the average person, the difference between a faint star and a scratch in the negative might be difficult to discern; thus, aesthetic standards provided the common template of understanding for both the astronomers and the engravers.

Similar to how pictorial standards provided the visual language for the emergent genre of Western landscape photography, it appears that the engraver was authorized to produce a background similar to those found in painting, masking out the astral surroundings to allow the main attraction—the nebula—to assume visual prominence.14 The artificially darkened sky did not threaten the construction of realism, and the conventions of Western painting served as a handy hermeneutics for making sense of incoherent visual material. In the late nineteenth century, the elided “craft” in the making of astronomical images signaled an unwelcome human agency in pictures thought to descend directly from nature.

The Digital Era and Interpretive Color

Figure 2. ‘Cone Nebula (NGC 2264): Star-Forming Pillar of Gas and Dust.’ Courtesy NASA, H. Ford (JHU), G. Illingworth (UCSC/LO), M.Clampin (STScI), G. Hartig (STScI), the ACS Science Team, and ESA.

The contemporary anxiety that surrounds “false color” stems from this perceived violation of a scientific objectivity purportedly guarded from human intervention. More than one hundred years later, the subjectivity of astronomical images is still under scrutiny and the same language—the distinction between the “correction” versus the “alteration”—persists in scientific communities.15 The age of Photoshop has further chipped away at photography’s evidentiary claim to truth, introducing greater room for tampering on the part of producers. Now, digital-born imagery can be endlessly transformed and reproduced at little cost and by a large number of the population. As the means of production are democratized, no longer a specialized or abstruse process, people are wary of these manipulations. And yet, it is often not the objectivity of the machine or software that’s called into question, but the intentions of the individuals using the machine. For example, an iPhone’s built-in image processing algorithms significantly enhance images taken with the phone’s low quality camera, and yet these images are not interpreted as “doctored” in the same way as images altered by Photoshop or Instagram filters. Similarly, it is not the raw data transmitted by the telescope that is seen to be error-prone—although errors do occur—but the human-made representations of this data.16 In short, the degree of individual “artisanal engagement” is still a problem with which to be grappled by both scientific communities and the general public alike. In the digital age, with the means of color manipulation broadly disseminated, the authenticity of these images as bearers of knowledge is cast into even greater doubt.

Although much has changed, the contemporary digital process of producing telescopic images involves the same extraordinary amount of mediation as the nineteenth-century engravings. In the creation of a modern astronomical image, a satellite first records photons of interstellar light and transmits them to earth in binary code. Scientific software translates this raw data – signifying the position of the particles of light that struck the detector during observation – into an event table that can be plotted on a graph. The graph is then “translated” into visual form by converting this digital information into pixels. These images are further processed through color mapping, artifact removal, smoothing, and cropping by a scientist or science imaging expert. For scientists, different color filters are used to “map” wavelengths otherwise invisible to the human eye, as symbols for which we have no physical correspondent, with different colorizing techniques often used to highlight specific items of astronomical interest.17

In short, astronomical images present a battle of interpretation between different and competing ways of thinking about the creation and meaning of images. Here, color is instrumental rather than aesthetic, functional rather than formal. In fact, color is employed in a similar fashion by doctors to read CAT scans and by geographers to interpret satellite images of the earth.18 While the aesthetic choices in color selection and composition are freely acknowledged by astronomers and image processors, objectivity in these cases is still maintained through the application of what Galison and Datson call “trained judgment,” in which the skilled, professional interpretation of raw data is believed enough to ensure the scientific validity of the picture.19 The confusion over false color, some might conclude, then lies in this basic disjuncture between different ways of decoding visual information in different epistemic communities. To dispel the public sense of deception, then, becomes a matter of educating non-expert viewers in seeing these images through the perceptual apparatus of astronomy: a distinctive professional vision based upon a particular set of practices and conventions—and, indeed, the websites of many observatories do just this as a matter of public outreach.20 21 But educating viewers in a “neutral” and “objective” astronomical perception—inculcating non-experts into the conception of the “scientific self”—may only serve to further downplay subjective visuality as derivative to the practice of science itself, even a kind of accidental decoration.22

In their seminal 1985 ethnography, Samuel Edgerton and Michael Lynch found that astronomers using ground-based telescopes similarly minimized the “craft” or “artisanal” aspects of the digital image-making process.23 However, rather than completely effacing the expressivity in an imaging process more or less widely known now to viewers, the “craft” element was bracketed within the category of non-expert “pretty pictures,” and the hierarchical distinction between scientific and aesthetic labor remained in place. The study exposed what Edgerton and Lynch call a “practical Cartesianism,” a split between the knowledge of the mind and sensory pleasure of the body. In this bifurcation, science remains “untouched” by affect; the aesthetic is not part of the practice of “real science”—a legitimate way of knowing—but is relegated to the sidelines and aligned with a consuming public.

When NASA image processor Zolt Levay calls the “pretty pictures” “a nice by-product,” subjectivity is again expunged from astronomical practices, ideologies, and daily experiences.24 In examining the presuppositions underlying the rhetoric of the “pretty picture” drained of its use-value, we see an active, knowing “scientific self” squared off against a passive, sensing public, too easily beguiled by spectacular beauty.

Pretty Pictures as Photographic Landscapes

The “pretty picture” is thus ontologically distinct from the scientific visualization. While astronomers may consider these deep space images provisional illustrations or tools to interpret data, non-experts are encouraged to see these representations as landscapes—direct reflections of a physical locality—not a “means to an end,” but complete in and of themselves as objects of visual consumption with unique pictorial qualities. At the same time that observatories educate viewers in the scientific reasons and processes behind “false color,” other parts of the NASA website encourage audiences to view the images as photographic pictures.

The Hubble Telescope, unveiled to the public in 1990, was perhaps the most hyped in this way, advertised as a “window on the universe” and a “tour guide” to exotic locales.25 In a nineteenth-century turn, the online gallery of the Hubble site encourages armchair travelers to “fill your computer screen with a Hubble image. Your body may be trapped at your desk, but your imagination can roam the far reaches of the universe with our cosmic visuals.”26 The titles of books marketed towards a general audience over time such as NASA’s 1968 Exploring Space with a Camera, the 1996 A Photographic Tour of the Universe, and the Smithsonian’s 2013 Your Ticket to the Universe: A Guide to Exploring the Cosmos, to name a few, only further perpetuate the idea that the images made possible by the telescope are documents of photographic truth.27 In this rhetoric, audiences can safely “know” deep space—an abstraction incredibly far removed in time and space from our daily experience of the world—because the scientific “eye” of the telescope-camera could be trusted to deliver an authentic view of this distant world, subordinated under our gaze. Moreover, portraying images of deep space as photographic landscapes is hardly politically neutral. As part of the conjoining of the state and Big Science in the middle of the twentieth century, this interpretation of the amorphous shapes of deep space as a type of travel is bound up in the popular Cold War reading of space as the final frontier, an untouched wilderness like the Western landscapes of centuries past.28 29 Incorporating these images into the genre of landscape photography helped create deep space as an object of American power; to visualize these outer most terrains as a picture was to exercise the surveying power of the gaze. As a result, the seemingly dimensionless forms of deep space were transformed into a marked territory, a composition, a picture that could be viewed and thus controlled.30

Figure 3. Buzz Aldrin with U.S. flag on the Moon on July 20th, 1969. Source: NASA Apollo Archive

While we might initially assume this kind of marketing rhetoric promoted by the Hubble gallery is separate from the neutral pursuits of a “pure” science, can American astronomy truly be divorced from its propaganda? Is to discount the sensory appeals of such public relations also to fall into a kind of “practical Cartesianism”? As science historian Robert W. Smith writes, “Remarkably, astrophysics, one of the least utilitarian of the sciences, became arguably the most richly endowed of all the sciences in the United States.”31 With vast amounts of federal funding expended on astronomical investigations under Big Science, the public has become shareholders in the project of space exploration. Like early photographs of Western exploration, visual evidence is created to justify—for both the public and lawmakers—the cost of projects growing drastically larger in scale. Moreover, these images function as rhetorical workhorses even within the agency itself where projects compete with one another for funding and labor. As Smith writes, “decisions concerning the space science program could not be made on purely scientific grounds. There were other factors to consider, such as funding, manpower, facilities, launch vehicles and the saleability of projects in the existing climate at the White House and on Capitol Hill – factors that only NASA could properly assess.”32 In such a bureaucracy, the space-based telescope is dependent on promotional maneuvers from the earliest phases of its construction. In this light, it appears that the public relations department of NASA is not subsidiary or separate from the modern practice of astronomy but constitutive of it as an essential component to the formation of complex, large-scale scientific operations. In other words, the “pretty picture” may not be just a “by-product” cleaved from the practice of “real” astronomy but deeply enmeshed within it. The appeal to the senses—from the emotional pageantry of shuttle launches to the psychedelic Hubble images—has made astronomy what it is today.

Subjectivity Exposed  

With their human-made elements brought to the fore, the temptation may be to repatriate these telescopic images as cultural products. As “art” they are realigned with notions of sensation, intention, expression and mediation. Punted back to the camp of “representation” from the “real,” their claims to scientific fact are thus weakened. The application of color particularly, with its associations of subjectivity, can be interpreted as downright unethical, assailing the truth claims of astronomy. A 1985 New York Times article by the Pulitzer-winning journalist and photographer Malcolm Browne, “Guilty of Disappointment,” illuminates the negative reaction to these gauche “neon-tinted” pictures:

Some of the lies perpetrated by astronomical pictures are unavoidable or even useful. False-color images enable scientists to discern all kinds of things that would escape notice in an ”honest” photograph. But there is a trace of deliberate mendacity having nothing to do with scientific purpose in some of those pictures. The very scientists who gave us those great Voyager planetary photographs, moreover, are among the culprits; they have candidly acknowledged that the vivid, enhanced-color pictures we saw of the Jupiter and Saturn flybys were distributed in deference to popular taste. Neon-tinted pictures very likely get better results than drab ones, when budgets come up for review.33

Here the image is set up in opposition to the mimetic fidelity of the “honest” photograph, its scientific integrity sacrificed to cheap Technicolor entreaties for popular support. It is allied with the public, commerce, and middlebrow taste, all in contrast to objective scientific description. The negative ethical implications of these colorful pictures are clear in Browne’s references to the “lies perpetrated” and “deliberate mendacity” waged by the “culprits.” The phrase “neon-tinted,” too, evokes nothing so much more than a Vegas shopping strip, an open bid for pleasure and consumption. This passage condemns scientists’ lack of restraint, a quality that is normally associated with the discipline and orderly control of the “scientific self.” A 2003 Los Angeles Times article, PR With Universal Appeal, similarly denounces what’s seen as visual trickery, calling into question the role of the “photographic artists” at NASA (as opposed to the agency’s preferred “imaging processing specialist”).34 Recast as “decoration” rather than “knowledge,” these images—which all represent invisible forms of light—appear to audiences as willfully misleading.

Figure 4. Star cluster NGC 346 in the Small Magellanic Cloud. Courtesy: NASA, ESA, and A. Nota (STScI/ESA)

Figure 5. Planetary Nebula. NGC 2440. Courtesy NASA, ESA, and K. Noll (STScI).

This sense of deceit is also echoed in scholarly rhetoric. In The Eye of the Hubble: Framing Astronomical Images, Evan Snider writes, “The danger, then, is that we will forget that images from Hubble are not direct representations of visual reality” as if such a representation of reality could be possible.35 He warns against the seductions of mimesis for even the “modern viewer” who may think herself  “too savvy to fall into this trap of machinistic rhetoric.”36 Writing about the camera in his Seen/unseen: Art, Science, and Intuition from Leonardo to the Hubble Telescope, the art historian Martin Kemp affirms: “Any representation that has been designed so that it bears internal signs of having been ‘taken from life’ or that is set in a textual vehicle in which such claims are embedded, asks to be taken on trust, and we are generally all too willing to acquiesce.”37 And so, as the aesthetic aspects of these images are publicly exposed, the astronomical image can become a kind of Pygmalion story, misunderstood as a deceptive imitation of the real. But yet again, this is a rhetoric that falls back on the philosophy of “visual trickery,” the illusion of appearances. While it is important to critically examine scientific representations as cultural objects, one must not measure these images against the yardstick of an imagined perfect representation. We find that when it comes to depictions of deep space—incredibly distant phenomena unhinged to the physical realities of Earth—even the basic proposition “taken from life” becomes an unstable measure by which to gauge authenticity.

The dialectic between the representation and the real that has come to define our understanding of the picture is thus particularly vexed when considering deep space. The reality, of course, is not that these images have “failed” to represent something real “out there” in the world—after all, what is a “representational image” of physical phenomena never to be seen by the human eye? No “original” exists. Although the public is encouraged to interpret these images as landscapes—photographic dispatches from the outer limits—we have no referent by which to judge the authenticity of these topographies, no physical mirror of understanding. This is subject matter not explanatory in any earthly terms. To acknowledge the human-made aspects of the deep space picture, the inevitable acts of individual conjecture and mediation involved in its creation, is thus to acknowledge the limits of human knowledge and perception.

And this perhaps accounts for why audiences are so bothered by evidence of “doctoring.” It points to our ultimate handicaps in knowing the world, the limits of our technological reach and comprehension. It is a loss of the power that comes with defining the world, the descriptive mastery over the unknown. For example, it does not bother us when red-eyes are removed in family snapshots because we know through first-hand experience what our family looks like.38 Not so with distant stars. And so common conceptual frames— “photograph” or “landscape”—are deployed to make sense of this foreign visual material, with the careful maintenance of objectivity reassuring us that what we are seeing actually exists. This debate over the veracity of the images can thus be understood as stemming from a need to domesticate and assimilate the unknowable, to wrangle it into sense by making it a picture. And so rather than judge the “realism” or “truthfulness” of the subject matter—in other words, the visual synchronicity of the picture with an exterior world only provisionally glimpsed—we must instead examine how this realness itself is constructed. Rather than partition further the practices of art and science, we must explore how these categories and their attendant claims to knowledge are discursively created. We must not decry the illusory image but question the set of epistemological assumptions that undergirds our beliefs about images, and the conditions under which the notions of trust and deception are created in the first place.

The author offers her heartfelt thanks to Kim Kowal Arcand, Abby Glogower, Alicia Guzman, Anther Kiley, Alex Marr, Doug Nickel and Brad Weslake for all their incredibly helpful comments and suggestions.


Anya Ventura is the Arts Research Writer for MIT’s Center for Art, Science & Technology. She became interested in outer space while working as the Research Coordinator for the artist Trevor Paglen’s project, The Last Pictures, a collection of images now orbiting the earth via satellite. She has an MA from Brown University in the Public Humanities. More on her work is available at

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