Shulou(Shulou.com)11/24 Report--

On October 11, the James Webb Space Telescope detected only narrowband data that was invisible to the naked eye. In order to let the audience see the visual images that can resonate, the researchers will use color palettes to give different elements a variety of colors, after a series of processing, such as noise removal, clipping and flipping, and finally produce beautiful celestial images.

In the first photos released by the Weber Space Telescope, the stunning appearance of the Carina Nebula is largely due to Alyssa Pagan. As a scientific vision developer at the Institute of Space Telescope Science (Space Telescope science Institute), Pagan's job is to convert the data captured by the Weber Telescope into beautiful visual images.

Pagan called the work a "combination" of data, aesthetic principles established after decades of scientific research, and subjective taste. There is a great distance between the telescope and the observed object. To observe distant celestial bodies in the universe, the Weber Telescope uses infrared spectra that are invisible to the naked eye. Researchers like Pagan must choose how to convert the data into visual images.

For example, color is a common problem for Pagan. The Weber Telescope has collected narrowband data after multiple exposures, which means that the infrared spectrum of the detected objects has a very small wavelength range, which is related to the presence of specific elements such as hydrogen, sulfur and oxygen. Pagan colors according to a principle called color sorting, such as the shorter wavelength of oxygen using the shorter wavelength of blue. Then different colors are superimposed to form the basis of the whole image.

However, because the wavelengths of hydrogen and sulfur are related to red, the color of hydrogen is usually yellowish in order to show clearer details in the final picture. This is the origin of the Hubble palette.

These images are sometimes called pseudo colors. But Pagan stressed that these colors are representative of real data. For example, in the image of the Carina Nebula taken by the Weber Telescope, the red part at the bottom is mainly composed of hydrogen and sulfur, while the blue part at the top is mainly composed of oxygen.

Image source: NASA Pagan said that only after applying these basic colors can the processing of celestial images become a "taste problem". She may move the entire palette up or down the spectrum to make the blue look purple, and vice versa. As a result, the contrast of different elements may be enhanced. In addition, it is also necessary to remove the scattered light produced by the telescope and so on. But different processing methods will get a completely different image. "I especially like to make things more ethereal and magical," Pagan said. "my method is a little whimsical-because it's space!"

The Pagans are doing this in part to evoke empathy with space images. Visual culture scholar Elizabeth Kessler (Elizabeth Kessler) investigates how the Hubble team of visual developers can make it easier for people to understand the vastness of the universe and use images to evoke a sense of awe of the unknown.

This practice has been continued in the Weber Telescope project. The image of the Carina Nebula captured by the Hubble Space Telescope is called Hills and valleys. The new image taken by the Weber telescope is called "the cliff in the universe".

However, the Carina Nebula is also presented in this way from an aesthetic point of view. Kessler deliberately stressed the importance of tailoring and orientation. "the birth of stars can be seen in many areas of the nebula. But they chose this region and combined it with the cloud edge to form a horizon," she said.

You know, there is no concept of "up" in space, and although images taken from the ground usually go up to the north and down to the south, "north" means nothing to orbiting telescopes in space. Kessler points out that the direction of the image of the Carina Nebula may be reversed in order to turn the dust cloud into something familiar to the audience.

"the orientation of the picture is determined from the beginning, because it feels the most natural," Pagan said. "it needs to be approachable. it feels like a mountain."

The goal of Pagan's work is to make these cosmic images more "understandable" to the average audience while remaining attractive. Image processing is "really helpful," Kessler said. the scale of what we see is beyond human understanding. in our experience, the closest thing to us is the mountains towering above us. "

This method is also very popular in ground-based astrophotography. According to popular science worker Dylan O'Donnell (Dylan O'Donnell), part of the reason is that using narrowband methods helps avoid light pollution. O'Donnell says ground cameras can be drowned out by light from buildings and streets. However, by keeping a very small band, "this allows people in the center of the city to take images similar to the Hubble image." Of course, a variety of palettes can be used to interpret narrowband data when processing images. For example, another popular method is the "CFHT palette" named after the Canadian, French and Hawaiian telescopes.

The difference between the Hubble palette and the CFHT palette mainly lies in the complexity of chromaticity sorting. While Hubble gives hydrogen a reddish-yellow color based on different wavelengths, the CFHT palette pushes sulfur to the top of the spectrum, creating a green-purple nebula that highlights different details. "it doesn't change science," said Heather Flewelling, an CFHT astronomer. "it just makes some features more obvious."

There are many combinations of different detection wavelengths and palettes, all of which result in different ways of data display and completely different aesthetic experiences.

What kind of palette to choose is a matter of personal preference. Although O'Donnell says most people prefer to be as natural as possible, his own work also highlights the benefits of using false colors to show details. He has taken two pictures of the Eagle Nebula, one in true color and the other in the Hubble palette. By comparison, the latter can better show the structure and depth of the nebula. The yellow-and-white dust stands out against the blue background of the Hubble palette, while in the true-color version, different shades of pink appear more insipid and more difficult to distinguish between details.

But O'Donnell said that because too many people use the Hubble palette, the hue image looks "a bit overused."

Source: the NASA Weber Telescope team is also making images in unexpected colors. In one of the recently released photos of Jupiter, Jupiter looks blue. Although Hubble's images of Jupiter show both blue and red, in the newly released photos, the famous Great Red spot looks white due to the reflection of sunlight. The palettes used in image processing are likely to highlight Jupiter's auroras, Pagan said.

For Kessler, this suggests that Weber's image processing may not continue to be too close to Hubble. "I wonder what the result will be," she said. "if more people go in this direction."

The direction of the Weber image will be a decision made by data and people, a combination of centuries of visual culture and billions of years of light traveling in space.

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