How a small team in Baltimore brought images from the Webb telescope to life
fFrom its orbit a million miles from Earth is the now operational James Webb Space telescope has finally returned his first pictures, including a deep field view of thousands of galaxies, shining like gems billions of light-years away. But as stunning as these images are, they would be nothing but a series of black pixels if they didn’t walk through the Steven Muller Building, a modest khaki-brick structure hidden among the trees on the Johns Hopkins campus BaltimoreMaryland.
There are few permanent features to alert the casual passerby that the building is the headquarters of the Space Telescope Science Institute (STScI), although a blue and gold banner hung over the main entrance reading “Go, Webb, Go!” ‘ was exclaimed. provides an obvious clue. STScI started operations Hubble Space Telescope on behalf of NASA and scientists in 1990, and the institution’s mission has now expanded to include Webb. STScI controllers helped guide the new space telescope through the deployment and commissioning process, and began capturing the first images with the large gold telescope in early June.
And those images don’t magically appear with brilliant colors and balanced brightness. The raw data captured by Webb must be processed, de-artefacted and colorized by specialists at the STScI who work behind the scenes to process all of the Webb images released to the press over the telescope’s years of science became. And it’s in many ways both an artistic and a technical process.
On June 24, about two weeks before the release of the first Webb images, Science Visuals developers Joseph DePasquale and Alyssa Pagan sat in their shared office surrounded by large computer screens and demonstrated how they created the first beamed back Webb images processed earth. With a mouse movement, Mr. DePasquale took Webb’s first deep-field image, a series of glowing gems, actually thousands of incredibly distant galaxies, and restored the image as it had come to him: a black screen.
“The pixel values are mostly dark because the sky is mostly dark and only the brightest regions show through at first glance,” he said. Mr. DePasquale and Ms. Pagans’ job is to use a software suite to increase the brightness of the image so people can see the darkest details without washing out the bright areas. “All this information is hidden here because it’s really, really dark.”
With a few more clicks on the keyboard, Mr. DePasquale increases the brightness in a process known as “scaling” the data, revealing a grayscale version of the Webb depth field. Adding color is a later step, but that’ll have to wait until Mr. DePasquale addresses another issue that arises from scaling the image to make it bright enough to see.
“Bright stars in Webb tend to become saturated to the point where the detector is no longer providing valid information,” Mr. DePasquale said. “If that runs through the pipeline, it will end up creating a black hole at the center of a bright star.”
This effect can be seen in the webb Image posted July 6 as a sneak peek, an orange starfield captured by the Space Telescope’s guidance instrument. At the centers of bright, spiky stars are black circles that look like holes burned through a film negative.
“We sweated that out as we got closer and closer to it [Webb image release] Date,” Mr. DePasquale said, but eventually he came up with a computer script that filled the black holes with the values of neighboring pixels. It’s the kind of novel solution that the Webb data requires, he adds, because unlike the well-known workflow for developing images from Hubble data, at Webb “the process is just in flux because everything is new.” .
Which Webb First?
Webb’s deep field image was the first of five images selected by STScI and Nasa to show the tangible results of more than 20 years and $10 billion spent on design, development, build, test , launch, deployment, configuration and commissioning were the most sophisticated telescope ever built. US President Joe Biden Preview of the deep field image from the White House on July 11, while the remaining four images were posted to Nasa’s website the next morning. The full set of images includes the depth field, the spectrum, or pattern, of light filtered through exoplanet Wasp 96 b’s atmosphere, as well as images of the Carina Nebula, the Southern Ring Nebula, and Stephan’s Quintet, a cluster of five trapped galaxies in a tight gravitational dance.
But which images the public would see first and what exactly they would look like was still a matter of debate on June 24.
“The charter we have is to show the world that the observatory is ready to do science, to celebrate being ready to do science,” said Klaus Pontoppidan, associate astronomer at STScI. He was one of about a dozen people in a small conference room on June 24 to discuss the images that would be released to the public.
“Almost nobody else in this building, or even at NASA, saw that,” added Dr. Added pontotopidan. “It’s just this room.”
The small group had met most mornings throughout the month to discuss the latest images, which were being processed by Mr. DePasquale and Ms. Pagan and displayed on a giant wall-mounted monitor. On June 24, discussion turned to which version of the Carina Nebula image would be released, an image captured by Webb’s near-infrared NIRcam instrument or his mid-infrared MIRI instrument.
While the NIRCam image highlighted the orange and gold dust clouds, MIRI peered through the dust to reveal more stars, but with the gas clouds emerging in shades of grey-blue against a red “sky,” a controversial aesthetic.
“To me, the grey-blue that turned out in the MIRI image is not attractive,” read one of many overlapping comments in the room.
But there was a third option presented by Mr. DePasquale and Ms. Pagan – a combination of NIRCam and MIRI images, a mix of perspectives that preserves the contrast of the MIRI image while retaining the rich detail and stunning colors of the NIRCam -Image superimposed.
“It’s like the best of both worlds,” Ms. Pagan said.
The group finally settled on the combination picture Carina, which the public saw on July 12.
But the creation of the Carina image reveals a different way in which creating visible images from Webb’s data is a creative process in its own right, particularly when it comes to the color process.
Returning to the fact that most raw Webb images are essentially blank to the human eye. The distant objects it images are in many cases incredibly faint, too faint to register in the color-sensing cone cells of the human eye. This often also applies to less exotic astronomical observations.
“Look through a telescope at a planet like Jupiter or Saturn and it looks almost black and white because the light is so weak that it really only activates the rods in your eyes and not the cones,” said Mr. DePasquale. “You don’t really get color information.”
Adding to this in Webb’s case is the fact that the telescope only sees in the infrared, wavelengths of light too long for human eyes to see, no matter how bright. Then, to make Webb’s images visible, Ms. Pagan and Mr. DePasquale must transpose frequencies of light that are invisible to the human eye into the visible part of the spectrum.
“Telescopes are equipped with filters to separate the different colors, and then we map those colors chromatically,” he said. “The shortest wavelengths of light are mapped to blue colors, then move from blue to green to red as you increase the wavelength.”
It’s a system that has worked well with Hubble, which only saw into the near-infrared, and so far seems to work well for Webb’s NIRCam, according to Pagan.
“But when we go into the mid-infrared with MIRI, we get something very different, which is challenging,” she said. To avoid garish color combinations like Carina’s MIRI picture, they had to get a little creative with the color mapping, “so it could be red, orange and cyan” instead of red, green and blue.
The process could be vastly different for scientists using Webb to study a specific aspect of a distant object, Ms Pagan noted. Instead of attempting to translate non-visible wavelengths of light into the visible spectrum in a way that makes visual sense, a researcher could request a color highlight based on a phenomenon of interest, e.g. B. organic gas clouds. Researchers can also use the services of her office when publishing the results of their research with Webb.
“There is a website where scientists can submit their proposals for a press release,” Mr. DePasquale said. “You can go that route, contact the news bureau here, and then we’ll determine if it’s actually print-worthy. If so, then it is up to us to process the data.”
Processing can be a lot of work, particularly at Webb’s – the Carina Nebula image took 16 hours to develop – and Ms Pagan and Mr DePasquale worked weekends in the days leading up to the release of the first Webb images. But the work is also so compelling that they would have digested the new images even without the urgency of the upcoming release.
“The first record came in on a Saturday morning and I had to go to Philly for a family reunion,” DePasquale said. “I’m at the party. And I’m like, ‘I just want to work on this picture.’”