Observing the Astronomical Sublime

Note – A few years ago, I was asked to review Elizabeth Kessler’s 2012 book Picturing the Cosmos: Hubble Space Telescope Images and the Astronomical Sublime. The review came out in a fairly obscure academic journal with far less exposure than Kessler’s fine book warrants. With the 25th anniversary of the launch of Hubble this week, I wanted to present the review to a wider audience and make a few additional observations.

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One can quibble about the details but the facts stand for themselves – the Hubble Space Telescope is the most influential (and certainly most expensive) science facility in human history. Its influence can be measured not just the number of scientific papers it has produced but also in terms of the global reach the images from HST have and the ways in which they have taken root deeply into the popular imagination.

The ways in which these images come to us are the subject of Elizabeth Kessler’s wonderful book Picturing the Cosmos. I encourage anyone who is fascinated by Hubble’s photographs and their impact on the visual imagination over the last quarter-century to pick up a copy.

Just writing that – a quarter-century – stands out. There is a generation of scientists now who literally cannot remember a time when there was no Hubble Telescope. The ways in which Hubble’s data is used and re-used have shaped astronomical practice. Look at this graph:

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This image alone makes it clear how Hubble has changed the ways in which astronomers do their science. Somewhere around 2003, the number of publications using data from the HST archive surpassed those produced from actual observations. The number has continued to climb. And, today, something like 40% of HST-related publications use only archived data.

In 1998, the Hubble Heritage Team was preparing to release a new image of the planetary nebula NGC 3132. Hubble Heritage images appear not just in research papers but on calendars, coffee mugs, and the walls of art galleries. This is partly why HST is so influential…they literally shape how many citizens and scientists around the world see the universe. When describing how a balance between aesthetic inclinations and scientific veracity was found for the NGC 3132 picture, one team member explained, “We tend to look for things that ‘look right.’ And what exactly looks right is maybe a little hard to quantify.”

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Look familiar?  NGC 3132; Source.

This quote come near the end of Kessler’s excellent and thought-provoking new book, captures a great deal of the tension inherent in making and viewing contemporary astronomical images. Such scientific images have an inherent aesthetic and artistic quality. As Kessler’s book reveals, they do all sorts of work besides “merely” conveying scientific information.

The “astronomical sublime” is central to Kessler’s analysis of Hubble images. Primarily focusing on the work of the Hubble Heritage Project, she expands on the sublime’s characteristics features (astonishment, the infinite, and even terror) and extends it beyond its origins with 18th century scholars like Immanuel Kant and Edmund Burke. Contemporary Hubble images not only reflect qualities of the sublime but also resemble earlier traditions in western art. We can compare Hubble images to famous 19th century landscape paintings by artists such as Thomas Moran and Albert Bierstadt.

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Thomas Moran’s Cliffs of the Upper Colorado River, Wyoming Territory (1882)

The famous 1995 “Pillars of Creation” image – a view of the Eagle Nebula – has parallels to, for example, those the towering cloud and rock formations found in Romantic scenes of the American West.

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These 19th century scenes of the American frontier once conveyed natural splendor to parlor-bound citizens. They also communicated the ideology of manifest destiny and the transformative power of the frontier as Frederick Jackson Turner famously noted. In similar fashion, images from Hubble reflect their own historical moment by stimulating public interest and continued funding for NASA’s continued exploration of the cosmic frontier. In the early 1990s, when the telescope’s initial spherical aberration threatened to undermine public and political support altogether, images from Hubble proved especially critical. They convinced scientists, politicians and tax payers that a hobbled Hubble could still produce good science and a repaired telescope even more so.

Kessler’s book blends the histories of art and astronomy with oral history interviews and observations of contemporary astronomers at work. She also engages with the work of other scholars who have considered the nature and use of astronomical images. The book, for example, finds common ground with Samuel Edgerton and Michael Lynch’s earlier work on digital image processing.1 Also critical are the ways in which astronomical images – especially the highly visible ones from the Hubble Heritage Project – perform functions besides those narrowly construed as “scientific.”

Look at this still from the 1990s show Star Trek Voyager what’s in the background? A Hubble image.

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Years ago I interviewed NASA administrator Ed Weiler. At the time, NASA was defending the budget for the James Webb Space Telescope (sometimes, but erroneously – I think – billed as the successor to Hubble). One of the things we talked about was the popularity of Hubble and how this helped sell JWST to a skeptical Congress. Weiler remarked – and I’m paraphrasing – that if he wanted to know which Hubble images were popular, all he had to do was watch Voyager (or check out the calendars and coffee-table books packed with Hubble images.)

Kessler’s treatment of HST images is far from naïve, however. Kessler explains how Hubble images are “doubly translated”, moving from object into digital data and then into image. This issue of conversion has long been an issue for astronomers. How a Hubble image is produced is as important as the image itself. Starting with proposal submission and moving to data collection, calibration, analysis, and presentation, we encounter persistent questions about the “objectivity” of scientific images. What constitutes a legitimate image when so much massaging and processing goes producing it? However, issues about authenticity existed long before the advent of digital images, starting when astronomical images were first captured via hand-made drawings and then recorded with photographic techniques.

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A different kind of archive…the plate stacks at Harvard College Observatory. Source

At the same time, there is something profoundly different about digital images. New tools and standardized formats developed in the late 1970s and 1980s facilitated the circulation of digital data. Meanwhile,image processing technologies (derived from classified reconnaissance activities) gave scientists greater flexibility in using contrast, color, and cosmetics to interact with their data. Although positioned as “rational” depictions of the cosmos, Hubble images reflect aesthetic and personal choices consciously made by scientists as well as the technological legacy of the Cold War. If these ideas and images intrigue you, check out Kessler’s excellent book.

  1. Michael Lynch and Samuel  Y. Edgerton, “Aesthetics and Digital Image Processing: Representational Craft in Contemporary Astronomy,” in Picturing Power: Visual Depiction and Social Relations, ed. Gordon Fyfe and John Law (London: Routledge, 1988), 186. []

Conversion Experiences

Saul, so we’re told, had his conversion experience on the road to Damascus. Astronomers had theirs in labs and machine shops starting in the 1960s.

By this, I mean that astronomers developed tools and instruments to convert traditional photographs – made of glass and emulsion – to digital zeros and ones. This began a process that would completely reshape how astronomers work. Once data was in a digital format it could move about more easily. Astronomers could work across wavelengths and share data they collected with different telescopes. To borrow a fashionable word from history, astronomy could become more transnational as data circulated not only across desktops but across national borders.

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Image from typical astronomical photograph, as negative. Stars are sharp and galaxies are fuzzy.

But first it had to be digital. One of the most innovative tools for taking astronomical photographs and converting them to digital format originated in the mid-1960s with a graduate student at Cambridge University.

In 1970, Ed Kibblewhite was a 26 year-old just a few months away from filing his dissertation. Like many in his professional cohort, Kibblewhite had moved into astronomy from another field; in this case, electrical engineering. In 1966, Kibblewhite proposed building an “automatic Schmidt reduction engine” for his dissertation.

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Kibblewhite, 1977, examining a photographic plate the old-fashioned way – with a light box and magnifier.

As Kibblewhite’s proposal suggested, its prime application was analyzing images taken at Schmidt telescopes, instruments whose optics are designed to take in much wider fields of view compared with traditional reflecting telescopes. To understand the data challenge posed by these large-scale survey telescopes, consider their output. The photograph itself is a negative; bright objects like nearby stars show as dark black spots while galaxies are fainter and fuzzier. A typical exposure recorded might contain as many as one million astronomical objects.

Kibblewhite’s graduate advisor approved his plan and, for the next five years, he designed and built what eventually became the Automated Photographic Measuring facility (or APM).

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View of the APM, late in its life. Source.

He estimated the initial cost at just under £33,000, a considerable sum in the late 1960s (and close to $800,000 in 2014…a substantial sum then and now). In developing his design, Kibblewhite looked to previous machines as something to improve upon. For example, astronomers had routinely built and used “measuring engines” since the 1950s. These instruments scanned photographs and electronically recorded their information such as the coordinates of stars and galaxies. Commercial firms like PerkinElmer eventually made “microphotometers” that allowed researchers to manually map the location of a star or galaxy on a photographic plate, measure its optical density, and convert it the signal into a value of the object’s actual brightness.

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Microphotometer from 1970s; made by Boller and Chivens. Source.

Kibblewhite decided to use a very bright laser beam as a light source for his APM. When rapidly moved, the scanner could process an entire Schmidt plate with a million or so separate objects about a hundred times faster and do so automatically.

For the actual image analysis, Kibblewhite received assistance from an unexpected source. In 1967, he met James Tucker, a cancer researcher at Cambridge’s Pathology Department, who was developing software to process images of cell nuclei. The ability to subtract the background as well as delineate the edges of “fuzzy” objects – cell nuclei or galaxies – was essential for both researchers and, when stained black, biological cells “looked just like star images.” Kibblewhite’s machine adopted a variation of Tucker’s program for the APM. Data from it – object’s position, total brightness, and distribution of brightness across it – passed through a series of computers before being stored on magnetic tape.

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APM diagram

Kibblewhite continued to refine and improve the APM for years after its 1970 debut; a good description is in this 1981 paper. He described the machine as a “national facility” available to “astronomers from all over the world” who wanted to convert and analyze their photographic data. Scientists would come to Cambridge with their own astronomical photographs, and once the conversion was done – it took about 7 hours to convert a typical plate into about two billion digital pixels – the astronomer could then “walk away with his data and start working out what it all means.”

Old rules of sharing and ownership still prevailed as converted data belonged to the individual scientist rather than going to a common repository for later use by another person. But these rules were gradually dissolving as data became digital. Besides fostering increased need for collaboration and an expanded professional skill set, the digital nature of astronomical data raised an increasingly important issue.

As opposed to the physical artifacts that characterized the photographic era, once data was digital, it became more movable. Data could circulate. And data that was easier to circulate had the potential to disrupt longstanding community traditions and norms about ownership and access. Friction that stood in the way of sharing and collaboration was oiled and smoothed. But first one had to be able to share the data. Conversion was a critical first step in the process.