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Aug. 3, 2022, 1:18 p.m.
Reporting & Production

“Space is for everyone”: Meet the scientists trying to put otherworldly images into words

“It is a lot like science writing in general. You need to have a very good understanding of the content.”

New photos from the James Webb Space Telescope let earthlings see farther into space than ever before. The kaleidoscopic images inspire awe and wonder and maybe even a bit of comforting perspective. But what if you’re blind?

Some of the fixes for people who can’t see images are more helpful than others, according to blind and low-vision internet users. One of the best and easiest ways to boost the accessibility of online content is alt text. Alt text is, yup, a text alternative to images that allows descriptions of photos, charts, maps, memes, and other visual elements to be read out loud to people using assistive technology like screen readers.

For the Webb telescope images, a large team of science writers, outreach scientists, and education specialists at the Space Telescope Science Institute helped write and edit alt text and the longer image descriptions. (The institute leads operations for the Webb and Hubble space telescopes and will do the same for the Nancy Grace Roman Space Telescope, named after NASA’s first chief female astronomer, once launched.)

Here’s the final image description for the striking Carina Nebula image, as one example:

The image is divided horizontally by an undulating line between a cloudscape forming a nebula along the bottom portion and a comparatively clear upper portion. Speckled across both portions is a starfield, showing innumerable stars of many sizes. The smallest of these are small, distant, and faint points of light. The largest of these appear larger, closer, brighter, and more fully resolved with 8-point diffraction spikes. The upper portion of the image is blueish, and has wispy translucent cloud-like streaks rising from the nebula below. The orangish cloudy formation in the bottom half varies in density and ranges from translucent to opaque. The stars vary in color, the majority of which have a blue or orange hue. The cloud-like structure of the nebula contains ridges, peaks, and valleys — an appearance very similar to a mountain range. Three long diffraction spikes from the top right edge of the image suggest the presence of a large star just out of view.

Tim Rhue, principal informal education specialist at the Space Telescope Science Institute (STScI), said the institute has been using alt text on sites like and for years, but that the team stepped up its efforts ahead of the Webb telescope’s big debut. (President Joe Biden revealed the first images in July.) This included work on a style guide for image descriptions, hiring the consultant Sina Bahram to help create better descriptions, and making other accessibility improvements to their website.

Rhue and Margaret Carruthers, the institute’s writing and design branch deputy, were kind enough to answer a few questions about the alt text process. Our conversation has been lightly edited for length and clarity.

Sarah Scire: Can you explain why NASA has started to add image descriptions?

Tim Rhue: There are a number of reasons that STScI is putting so much effort into developing quality image descriptions. Our primary reason is simply to share astronomy with as many people as possible. Space is for everyone. No one should be prevented from experiencing the wonders of the universe because of a disability. There are blind astronomers out there who do their work through sonifications of astronomical data; there is no reason other blind or visually impaired people shouldn’t be able to appreciate space. Astronomy is so often the gateway to people’s interest in many fields of science, so we are always working to make astronomy exciting, engaging, understandable, and relevant to everyone we can.

We also recognize that image descriptions help everyone, including people who have no visual impairment at all. There is a lot going on in the images, and a text description of the visuals helps draw attention to the primary points. When writing articles, captions, scripts, etc., we are often constrained by word counts. These extended descriptions can give us the ability to focus the audience and explain connections between parts of an image (or graph or infographic) that might not be immediately apparent, and that we don’t have room to point out elsewhere.

Secondarily, as a government organization, NASA is required to provide an accessible website in accordance with section 508 of the Rehabilitation Act of 1973. A new rule was adopted in 2017 by the U.S. Access Board that requires compliance with the Web Content Accessibility Guidelines 2.0 level AA standard. That requirement applies to our work at STScI as well.

Scire: What were the biggest challenges to writing these particular image descriptions?

Rhue: There are a number of challenges ranging from the complicated nature of some of the images to the short timeframe between image finalization and release. However, the biggest challenge is connected to the otherworldly nature of these images. Galaxies and nebulae and gravitational lensing are not things that most people know much, if anything, about. In these descriptions, we had to take care to describe what features look like. We can’t assume folks know what we mean by those terms.

Margaret Carruthers: What Tim said! Describing objects in space is very different from describing familiar scenes on Earth. In addition to being careful about terminology, we also have to be careful not to introduce misconceptions. It is a lot like science writing in general. You need to have a very good understanding of the content. You also need to have a good understanding of the purpose of the description, the purpose of the image, and the audience who will use the descriptions. I frequently had to go back to the caption or article or some other resource to make sure my description was scientifically as well as visually accurate.

In addition, writing detailed text descriptions — as opposed to basic 60-character alt text — is relatively new for us. We have a large writing team, and each writer has slightly different experience, expertise, and style of writing. For this project, we thought it was particularly important to maintain as much consistency as possible in terms of style and organization. This is important for the audience, so that they can focus on the content rather than the format. But our style and style guide for text descriptions had not completely been established yet. What we decided to do is have one writer — me — take the lead in establishing the style and ensuring as much consistency as possible. We are not 100% there, but I think this approach worked well.

Scire: Do you have a particular favorite description out of the ones you’ve written?

Rhue: My favorite as an editor is the Emission Spectra from Webb’s First Deep Field. It is not just an image, it also includes a series of spectra that demonstrate the how we know just how old the light we are seeing from different galaxies in the deep field is. Graphs are typically tougher to make interesting and relevant to folks. I think the description of them here does an excellent job of both painting a picture of the graphs with words and really drawing out the main science takeaway that is so apparent visually.

Carruthers: My favorite in terms of the science visuals is the exoplanet light curve. This is in part because I worked on this graphic and am somewhat biased, and in part because I loved communicating how beautiful the light curve is and what is physically happening during the observation.

However, it’s the beautiful Webb Science Themes graphic, which we used as the keystone image on the general press release, that I enjoyed writing most. I was not involved in designing this graphic at all. When I saw it, I was immediately drawn to it visually. But it was only when I started to describe it that I realized how smart it is. Every line, shape, and color pattern has a purpose. Even the arrangement of patterns and shapes is meaningful. The jagged line is a spectrum, representing the majority of Webb observations. The hexagon is the mirror and mirror segments. The shapes are objects and processes that Webb will study. The arrangement moves from ancient/far to recent/near, as does the color scheme of red to purple.

Scire: What advice do you have for people attempting to describe space images in words?

Rhue: Work with people who use these descriptions. We worked with folks outside of STScI in advance of getting the images, and with someone inside after receiving them. It’s difficult to strike the balance required to maintain objective accuracy about the images and convey the awe-inspiring nature of viewing them and simultaneously avoid jargon while remaining succinct enough to maintain people’s attention.

On top of that, the science content is often necessary to understand the descriptions of the images. We used a combination of image captions, release text, and the image descriptions themselves to convey that together. Working with people who use these descriptions to develop the guidelines around writing them and review the actual descriptions was invaluable in making them work.

Carruthers: Here are a few top tips regarding the process and the descriptions themselves.

  • Just get started. Recognize that as with a lot of writing, the first attempt might be difficult and you will probably use the backspace key a lot. Be prepared to start over a few times. You’ll get the hang of it soon enough!
  • Know what the purpose of the image is (content, intended audience) and the purpose of the alt text. Not all alt text has the same purpose. (The alt text for thumbnails is different from that on our main image page.)
  • Start with the big picture. Orient the audience first. Then go into the details of each component of the image. Use directional/positional terms (right, left, above, below, 9:00 position, horizontal) and geometric/mathematical descriptions (circular, diamond-shaped, concentric), and feel free to describe how things look in terms of other familiar objects or processes. Point out how things are related to each other both conceptually and spatially. If something is missing from the image that the audience might expect to be there, point that out too.
  • Think about ways to standardize descriptions for types of visuals. For example, we created a modified boilerplate structure, like a fill-in-the-blank, for the so-called “compass” images. These are the images that include compass arrows, scale bars, and color keys, which all have the same components. Modified boilerplate is easy for the writer to compose, and a standard format is easier for the audience to read.
  • Have the lead writer or subject-matter expert review the description to make sure it is accurate and communicates what they had intended with the image.
  • Tim’s point about having review by members of the audience you are trying to reach is really important. One exercise we did as a team was very instructive: I wrote an extended description of a mystery graphic. I then read it out loud while the team made sketches of what they imagined the graphic looked like based on my description. We were able to identify which aspects of the description were effective, and which needed improvement. It was also interesting to see how each person’s prior knowledge of the content influenced the mental picture they were able to produce.

One last thing: Writing an extended description can also be a really important part of the content development and graphic design process. There have been a few cases, though not on this particular project, where we discovered content errors in the graphics while we were writing the descriptions. In some other cases, describing the graphics revealed design or communication flaws that we needed to address. My point here is that I see numerous advantages to developing extended descriptions.

If you, like me, saw some scary headlines about permanent damage to the Webb telescope and wailed “Can’t we have one nice thing?,” know that a few micrometeoroids are not slowing the mission down. The telescope expects to exceed its original scientific objectives and take images for the next 20 years. You can keep up with the discoveries via images, alt text, and image descriptions here.

Photo of the Carina Nebula taken by NASA’s Webb Telescope.

Sarah Scire is deputy editor of Nieman Lab. You can reach her via email (, Twitter DM (@SarahScire), or Signal (+1 617-299-1821).
POSTED     Aug. 3, 2022, 1:18 p.m.
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