Infrared imaging allows JWST to see celestial objects that were previously hidden by thick clouds, and also has the advantage of taking into account the redshift of light in space. Therefore, it allows us to look at ancient and distant stars and galaxies in the Early Universe.
JWST (also known as “Webb”) has given us a new perspective and a new method of viewing events from the distant past (about 13.5 billion years ago).
However, the modified eye it provides does not possess the same mechanics as the human eye. Instead of observing the visible light spectrum (which humans can see), JWST prefers to see infrared light over other light spectrums. Since the eye cannot see most of the light released by celestial objects, it is appropriate to refer to it as the “new eye” given its innovative capabilities and findings.
But what are the advantages of seeing the infrared range at longer wavelengths, such as microwave and radio wave spectra? Before answering this, you need to understand that different light spectra are just different wavelengths of energy produced by the same light source (see image below). When the wavelength is shorter, the energy carried by the light is greater. That’s why we must avoid the UV radiation emitted by the Sun! These are powerful wavelengths that can cause DNA damage.
Electromagnetic spectrum; The wavelengths of energy produced by a light source (photo credit: udaix/Shutterstock)
What are the spectrums of light? And what do other telescopes use for imaging?
Six of the seven spectrums of light are invisible to us. As a result, our eyes can only see a small percentage of any object that produces light, the “visible light” wavelengths, which range from 4྾10-7 to 7྾10-7. As shown in the chart above, radio waves have the longest wavelengths, gamma rays have the shortest wavelengths, and infrared has a longer wavelength than visible light.
The name “infrared” is used because this range of light lies slightly below the wavelengths of visible red light, while wavelengths above the visible spectrum appear more blue/violet, hence the title “Ultraviolet”. So what do light spectra have to do with telescopic imaging?
Telescopes use detectors and cameras to filter out different wavelengths, ensuring that only the desired wavelengths are collected and electronically transformed for display. Compared to its predecessors, JWST has numerous sensitive detectors (including the Mid-Infrared Camera and the Near-Infrared Camera) to see the full spectrum of infrared light and give us sharper and more detailed pictures of light coming from billions of light years away. .
On the other hand, the Hubble Space Telescope detects light in the visible spectrum, while the Spitzer Space Telescope observes light in a shorter range within the infrared spectrum. In addition, the Chandra X-ray Observatory sees light in its X-ray spectrum. As a result, we can say that each telescope offers us several perspectives to observe the universe.
Ranges of the electromagnetic spectrum that different telescopes focus on (Photo credit: James Webb Space Telescope/Wikimedia Commons)
What are the advantages of using infrared radiation in telescopes?
Because different wavelengths of light show different processes and events in space, using the infrared spectrum presents us with a different perspective and lens for our Universe. As a result, there are several reasons why infrared is favored over longer wavelengths such as microwaves or radio waves. The ability of infrared light to pass through dense, cold clouds of dust and gas (compared to other wavelengths), a phenomenon known as “redshifting,” and the relationship between wavelength and temperature are the three critical reasons for JWST to use infrared observation. .
Transparent clouds?
Infrared radiation has the unique ability to penetrate thick clouds of dust and gas that other wavelengths of light cannot penetrate. When viewed through the Visible or UV ranges, these cold, dense clouds are opaque because the tiny dust particles inside can absorb the shorter wavelengths of light. Consequently, when these short wavelengths are used for imaging, it prevents light from objects behind or within clouds from being detected, and only the brightness of the cloud is noticeable. This is inconvenient, as within these clouds are star-forming zones!
After being scanned with infrared light, the dust begins to lose its ability to mask and obscure anything within and behind it. JWST is therefore able to see through objects that previously seemed impenetrable, and will eventually reveal the first stars and galaxies in our universe that were previously hidden.
Webb (infrared) and Hubble (visible light) view of the Carina Nebula; there is more detail in the Webb infrared image, as the Star’s nursery can be seen within the nebula. (Photo credit: Claudio Caridi/Shutterstock)
Redshifting can be confusing
To begin with, one of JWST’s key goals is to examine some of the first stars, galaxies, and planets that formed after the universe began. As a result, Webb must analyze areas of space that are unimaginably far away! As we look further into space, we can look further back into the past, because of the time it takes for light to travel and reach us. From a cosmic point of view, the speed of light can seem quite slow to astronomers!
Here the principle of redshift is introduced, which can sometimes be confusing, but let’s try to understand it now, since it is an important physical phenomenon that occurs in light waves. In the 1920s, none other than Edwin Hubble discovered that the Universe is expanding at an accelerating rate! He also observed that as we look further into space, objects move away from us faster due to the expansion of the universe, causing a redshift.
As the universe expands, the light emitted by ancient and distant objects extends to longer wavelengths. As a result, light from galaxies and stars in the early universe would have had its wavelength stretched so much by the expanding space-time fabric that it is now detected primarily in the infrared spectrum.
Original (left) and stretched (right) wavelength and distance between Earth and a distant galaxy. (Photo credit: VectorMine/Shutterstock)
This phenomenon of increasing/stretching the wavelengths of light into the infrared spectrum is called “redshift”. So Webb needs to look at the ancient universe with infrared detectors, to see some of the oldest light that has been “redshifted” over the course of 13.6-13.8 billion years !
Thermal eyes in space
Let’s consider thermal cameras for a moment. All of these cameras, like the JWST, contain infrared sensors. From airports to outer space, infrared radiation is best at detecting even the slightest changes in temperature, making it easier to understand temperature-related concepts such as luminosity, brightness, molecular composition, etc. Contrary to common belief, many celestial objects, such as nebulae, planets, and ancient stars, are actually rather cool (compared to bright stars).
Above is a thermal (infrared) scan of a person’s hands. In these scans, the blue regions are cooler, while the yellow/orange/red parts are warmer. We are conditioned to associate red with heat, but this is only true in thermal imaging, for conventional reasons. In the electromagnetic spectrum, bright blue is significantly hotter than bright red! (Photo credit: Cipta studio/Shutterstock)
We can detect infrared light to infer what is hidden by massive objects, such as dust clouds, that are otherwise opaque to visible light. This is possible because the colder (less energetic) something is, the longer its wavelength. Light, brightness and temperature have a direct connection that can be better noticed and understood when using infrared radiation, since older stars and galaxies are cooler and less energetic.
Stars that are younger and hotter radiate more visible light!
conclusion
Understanding how infrared works allows us to recognize that it has more benefits than other wavelengths of light in terms of discovering the earliest structures in the universe. In addition, scientists will often combine data from “visible light” telescopes (Hubble) with infrared telescopes (such as JWST) to create a composite image. Data from each telescope is merged to provide even more detailed images. So don’t worry, no one will ever forget what Hubble accomplished for us and will continue to accomplish. Fortunately, we now have more cosmic eyes than ever before!
Hubble, Webb and their combined image of M74 – The Phantom Galaxy (photo credit: NASA’s / Wikimedia Commons)
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