Cover image: JWST with its solar panel deployed, shortly after release from the Ariane 5 launch vehicle.
Credits: NASA, ESA
The James Webb Telescope is out there giving us absolute gems in the form of data about the origins of our universe. It is a fantastic extension of the capabilities of the Hubble Space Telescope. But not everybody really understands these images. There are a lot of questions that come up in people’s minds, like how are these images clicked, does the universe look exactly how we see in these images, what does the processing of the photos mean, what are we looking at, and so on. I recently attended a live stream of a discussion between engineers and scientists from NASA about the processing and interpretation of the images from the James Webb Telescope and the Hubble Telescope, which cleared several of my doubts as well.
Contents:
- Ways of “seeing” things
- Why infrared?
- What does the James Webb Telescope see?
- Taking the help of music
- Does the processed image depend on who processes it?
- The use of alt-text
Ways of “seeing” things
There are many ways in which one can see things. I do not mean other senses like hearing or touching. I mean specifically seeing. The way our eyes work is that light photons reach our eyes and the cornea and iris focus them on a tissue called the retina. Special cells convert these light photons into electrical signals and the optical nerve sends them to the brain, which paints a picture for us. Something like this:
But this is just one way of seeing things. Our eyes see the photons bouncing off things. But there are so many more types of particles. Read the section The Standard Model (How the universe works) – Science in Ten Minutes for a quick and easy understanding of the types of particles that exist. In short, there are at least 16 types of mass and force particles, and photons are just one of the types. Our eyes are meant to see only photons of a certain range of wavelength. But does this mean that all the other things happening in the universe are invisible to us? Not at all. We have built devices that will perform the same function our eyes do, just using particles other than photons.
The James Webb Telescope is a way of seeing the photons that our eyes cannot see – the infrared. We all know the rainbow colors – Violet, Indigo, Blue, Green, Yellow, Orange, and Red. Look at the image of the rainbow below. If we go from bottom to top, the colors go from violet to red.
But what’s there above red and below violet? There are more colors that we cannot see. That’s why we call the range of colors a human can see the visible range. The infrared light falls in a range above the red color on the VIBGYOR🌈 scale (or colors of a rainbow). However, we did not want to miss out on everything else happening in the universe, so we invented a way to see beyond the red. Likewise, there are other techniques to see the colors below violet as well. But infrared is special.
Credits: NASA and J. Olmstead (STScI)
We are mesmerized by the beauty of the world that we see with our eyes; and that is just photons. Now imagine the beauty of the universe if we could see all the different types of particles in the universe!
Why infrared?
We have said a lot of times before that light is basically photons. But when scientists talk about wavelength, wavenumber, etc., and say that light is a particle and wave, it gets confusing. Sometimes we even picture photon particles moving up and down like riding a wave. But it’s not like that and if we ask a science person, they say that it’s not simple and cannot be explained if you don’t know optics. However, it is far from the truth. Science is for our understanding of the universe, and if we are not able to explain things to people, then we have failed as scientists to make life easier for people.
Let’s try to understand differently. Please go ahead and read the section on The Standard Model – How the Universe works on my Science in Ten Minutes page if you need a small refresher. It will take you less than ten minutes to understand the concept. From this, you will have an understanding that a photon is a force, which controls mass particles. That’s why photons don’t have mass, and you can’t see photons themselves but photons help you see things (Science in Ten Minutes – Light and Vision). As the photon forces travel through space or anything for that matter, they radiate a field around them. And this field moves like a wave, oscillating like a string. Depending on the photon’s color, this wave can be shorter or longer. Infrared light is a section of light that has long waves i.e. a long wavelength. So, it is able to pass even the dense regions of gas and dust in the universe without much scattering and reach us, making it ideal to look at things that are billions of light years away (How big is outer space for real?) In fact, recently scientists were able to look at an extragalactic structure behind the Milky Way galaxy using infrared light, which was earlier not possible due to it being hidden behind the Milky Way galaxy.
What does the James Webb Telescope see?
The most common question is whether the James Webb Telescope sees what we would see in case we went to space. So, if you go to space and look around, you will stars whose visible light is able to reach your eyes. Otherwise, it will just be black, empty space all around you. But if we start detecting other particles, like infrared, gamma rays, etc., we will see that space is filled with some kind of radiation. So, when the James Webb Telescope went to space, it saw all the infrared radiation and captured images of that. These images are sent back to scientists on Earth and they process these images to the scale of colors that we can see (VIBGYOR 🌈). In fact, the visual input of the world has several methods. Humans use their eyes for taking visual input. But even for humans, there can be several variations. Most commonly, we see between the visual wavelength range of violet to red (VIBGYOR). Some humans with color blindness see some colors or black and white. Likewise, instruments can be designed to “see” the required wavelength.
Here are two images of the same “Cosmic Cliffs” of the Carina Nebula. See the image taken by the Hubble Space Telescope first:
Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA)
Now see the same taken by the James Webb Telescope:
Credit: NASA, ESA, CSA, STScI
The Hubble image is not bad, but this comparison is just to show that the two telescopes “see” different types of radiation in the same location in space, and thereby provide two different interpretations of the same. But none of them is wrong.
Taking the help of music
Music can help us understand the processing of images from the James Webb Telescope. If you want to sing a song, but the octave is too high for your voice to reach, what do you do? You would take the same notes and tune, but choose a lower octave that your voice can reach. Now you can sing the song. The conversion of the images from the James Webb Telescope is the same process in analogy as converting a piece of music from a higher octave to a lower octave. The song remains the same, but the scale changes. Likewise, the image remains the same, but the scale changes from infrared to visible range.
Does the processed image depend on who processes it?
Yes, 100%. The processed image can use different colors depending on how the scientist chooses their palette. But the message conveyed by the image remains the same. We just need to look at the scale along with the image and read what each color represents, and we will have the same story irrespective of the set of colors used.
The use of alt-text
Recently, the importance of using the alt-text has been realized in all the fields of study. Alt-text means alternative text to images. I mentioned earlier that humans can have different vision variations. While the most common is to see from Violet to Red, which we call the “Visible Range”, some humans also have color blindness. In this scenario, some can see only black and white colors, some can see the color red as green and brighter, and other variations. Here is a small idea of what people see under these conditions:
These people might see a very different scale of colors than initially intended. In some cases, the data can easily be misinterpreted. In order to counter this scenario, the idea of having an alternative text was conceived, which will be built into the image file. This is also helpful for people with complete visual impairment. For any image which conveys an idea, a description is included and can be read by anyone. The advantage this has over a caption is that even when the image itself is forwarded without captions, they can access the alt-text because it is coded in with the image. This idea has now inspired me as well to include an alt-text for each of these images to make my articles available to all. The scientists processing the images from James Webb Telescope are taking this into account and are now including alt-text with all their data.
Just like the James Webb Telescope sees infrared radiation, the Hubble Space Telescope sees ultraviolet and visible light radiation. We now have a flavor of what telescopes see in general and how scientists read those images. So, the next time you see a post from NASA, ESA, etc. with beautiful images from the universe, you know how to read the image. These are just the views of the universe using the electromagnetic spectrum. There could be so many more ways to “see” things. Do you know any?
The biggest problem is that we are not able to see ourselves as sitting on a space rock floating in vast space. The space around our planet seems empty, yet is filled with all sorts of energies and radiations. And even if we cannot see some things with our eyes or other instruments, they still exist. We must keep our pace toward finding everything around us. We realize that the Earth, Sun, Moon, other planets, in fact, our entire solar system, galaxies, stars, etc. are moving at a given speed through the universe. But we never really think about where is it coming from, and where it is going. The bigger picture coming soon.
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