The Mechanics of the Webb Space Telescope: How NASA ushered in the next great era of astronomy

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As a New Yorker, I would say that trying to spot a star from Times Square is nothing more than a fool’s errand.

To catch a glimpse of even one of them, you’ll have to squint past fluorescent streetlights, flashing billboards, stock market tickers, and other illuminated distractions. You’d better take a train a hundred or so miles north of the state. There, stargazing no longer requires any effort. A breathtaking sequin canopy hangs over you, whether you like it or not.

But even from the deepest, darkest, most distant place, you will never see every single star with the naked eye. You cannot physically see all the galaxies, nebulae, exoplanets, quasars – I could go on – in your field of view, even with your favorite standard optical telescope. There are still billions and billions (billions) of cosmic phenomena. It’s just that our human eyes are not designed to see the light they emit. It’s called infrared light.

Thus, quite a few cosmic treasures remain invisible to us. However, fortunately, this does not mean that they are outside of us.

As Stephen Hawking once remarked, humans are unique in that they always find a way to transcend our earthly limits. We do it “with our minds and our machines”. And, of course, over the years, astronomers developed fascinating infrared workarounds that eventually paved the way for NASA’s James Webb Space Telescope.

Fighting human limitation

High-budget space telescopes like NASA’s Hubble and Spitzer are already shedding light on some of the secrets of cosmic infrared rays. They contain instruments that scan the sky for elusive light and then translate that information into signals that human pupils can understand. This, in turn, allows us to see many things in the universe that are normally hidden from our eyes.

A group of the faintest galaxies in our universe, detected by Hubble's infrared detectors.

The famous Hubble deep field image seen through the infrared detection lens. These bright spots are not stars. Each of them is a whole galaxy.

NASA, ESA and R. Thompson (University of Arizona)

However, if these massive telescopes are the first and second episodes of a series of infrared astronomical observations, the powerful new agency Webb Space Telescope – the first set of full-fledged images of which was released on July 12 – this is a brand new season.

Levels above the infrared capabilities of Hubble and Spitzer, the JWST is literally made to work.

Comparison of the bright Orion Nebula in infrared and non-infrared.

Enlarge Image

Comparison of the bright Orion Nebula in infrared and non-infrared.

This composite image compares infrared and visible images of the famous Orion Nebula and its surrounding cloud. The infrared image was taken by NASA’s Spitzer Space Telescope and the visible image was taken by the National Optical Astronomical Observatory headquartered in Tucson, Arizona.

NASA and others

The groundbreaking telescope is a $10 billion gold-plated machine stuffed with infrared detectors, high-tech lenses, and programmed with super-powerful software. His holy grail device is called the near-infrared camera, or Nircam, and it will spearhead the process by collecting a plethora of infrared signals from deep space for astronomers to view on the ground.

This is why JWST is often said to promise to reveal an “unfiltered universe”.

Looking through a JWST lens instead of a standard optical telescope would be like looking at the stars from my hypothetical New York dark zone instead of Times Square. In both cases, there will be a lot more sparkles, even if you are looking at the same sky. It’s just that in our Shadowy Dark Zone analogy, we see extra stars because light pollution doesn’t shackle us. JWST, on the other hand, collects infrared light from deep space and decodes it for us.

It will point to the same universe that Hubble has explored for decades and scientists have studied for centuries, but it will access luminescence that we cannot see, perhaps revealing hidden cosmic phenomena such as violent black holes, exotic exoplanets, grand spirals. galaxies and… maybe even signals of alien life?

His first images have already captured a lot more than we took our breath away. In fact, the NASA staff who first saw the JWST “first light” images said they were moved to tears. “What I saw touched me as a scientist, as an engineer and as a person,” said Pam Melroy, NASA Associate Administrator.

Infrared and non-infrared comparison of the Lagoon Nebula.

These images, taken by NASA’s Hubble Space Telescope, compare two different views of the seething heart of a vast stellar nursery known as the Lagoon Nebula. On the left is the standard optical version. Right infrared.


But before we delve into the specifics of JWST infrared mechanics, we need to talk about the electromagnetic spectrum. More precisely, a bit of a mystery that he presents to us humans.

Why can’t we see infrared light?

At some point in your life, you may have wondered what it’s like to see a new color. The one that can’t be described, how “green” doesn’t really have a definition other than “caterpillar hue” – or, if you’re an open mind, “550 nanometer wavelength.” After some thought, I bet you’ve come to terms with the unsettling reality that you’ll never know the answer.

This is because colors are nothing but the result of the reflection of light from some source.

Different colors are dictated by different wavelengths of light, which can be represented as winding zigzags of different proportions. For example, when we see a blue umbrella, our eyes pick up narrower blue waves coming from the waterproof material. While admiring a fiery sunset, our eyes perceive longer and calmer red and yellow waves.

All these wavelengths are clearly organized in the so-called “electromagnetic spectrum”. But here’s the problem.

Electromagnetic spectrum diagram showing which regions Hubble and Webb can see.

This infographic illustrates the spectrum of electromagnetic energy, highlighting in particular the portions detected by NASA’s Hubble, Spitzer, and Webb space telescopes.

NASA and J. Olmsted [STScI]

While there are an infinite number of wavelengths of light, humans can only “see” one tiny part of the spectrum: the visible light region, which includes the colors of the rainbow. That is why we will never experience the pleasure of viewing a non-rainbow color.

Our bodies won’t let that happen, and there’s nothing we can do to change that—except, of course, building a super-powerful telescope.

Spying on secret wavelengths

Because infrared light goes beyond the region of visible light, despite its name, it does not appear red. It doesn’t look like anything. It’s actually better described as a thermal signature – we can “feel” the wavelength of infrared radiation, which is why many thermal imagers include infrared detectors. Firefighters, for example, use infrared light to find out where a fire might be raging in a building without going inside.

But specifically for astronomy, the invisibility of infrared wavelengths is a serious problem.

The universe is expanding. Constantly. This means that as you read this, stars, galaxies, and quasars — superluminescent objects that act like cosmic lanterns — are traveling farther and farther from Earth. And as they do so, the wavelengths of light they emit gradually stretch from our perspective, like pulling on a rubber band. They extend, retract, and stretch until they reach the red end of the spectrum. They are “redshift”.

A reddish image of the center of our Milky Way, dotted with a huge number of stars.

The center of our Milky Way is usually hidden from ordinary optical telescopes due to clouds of dust and gas. But the Spitzer Space Telescope’s infrared cameras were able to penetrate much of the dust, revealing stars in the crowded galactic center. The upcoming James Webb Space Telescope could offer an even more spectacular spectacle than this, bringing out fainter stars and sharper detail.

NASA, JPL-California Institute of Technology, Susan Stolovi (SSC/Caltech), etc.

Take, for example, a star born shortly before the beginning of time. At some point, when the Earth appeared, this star could emit waves of blue light towards our young planet. But as it moved away, in tandem with the expansion of the universe, the wavelengths of blue light began to lengthen from Earth’s viewpoint, getting redder… and redder… and redder.

“Redshift is the stretching of light toward longer wavelengths that occurs as light travels through an expanding universe and can be used to measure distance,” said Paul Geithner, JWST deputy project leader.

In fact, he said, Nircam JWST “will take a series of images using filters that capture different wavelengths and use the brightness changes it detects between those images to estimate the redshifts of distant galaxies.”

Eventually, however, these wavelengths fall outside the visible light spectrum. They penetrate infrared waters and disappear from sight with the naked eye. Consider again the ancient star example.

Now, billions of years later, these slowly reddening wavelengths have, from our point of view, moved completely into the infrared region of the spectrum. The ancient star sends us only such starlight that our eyes cannot see.


In this collage, you can see an image of all of Webb’s main instruments. These are not the final, full-color results from the “first light” telescope. They just test products.


Stars and galaxies, MIA

This means that all distant, ultra-rare and probably information-rich stars and galaxies are invisible to us, as well as everything that is illuminated by these stars and galaxies. We are missing bits of the history of our universe – its initial chapters.

But thanks to infrared detectors, JWST’s infrared detectors were able to show us those missing pieces. They could explain what space looked like in the first moments after the Big Bang. They could also find distant exoplanets floating among their own exomoons and look for distant artificial light that could signal extraterrestrial life. They will offer us a picture of the universe that is clear enough to remind us of our microscopic place in it.


Comparison of images of the Monkey’s Head Nebula taken by Hubble in the visible and infrared ranges. Although Hubble has some infrared capabilities, it is nothing compared to Webb.


Also, to take it one step further, infrared waves have the added benefit of being long enough to travel through matter, including thick, huge clouds of stardust. That way, if JWST picks up infrared light coming from such a cloud, it can paint a picture inside – perhaps even the birth scene of ancient stars.

“It is not clear how the universe evolved from a simpler state of only hydrogen and helium to the universe we see today,” Geithner said. “[T]The Webb Telescope will see the far reaches of space and an epoch of time never seen before and help us answer these important questions.”

But the most desirable aspect of JWST is that, in addition to the questions that scientists have been asking for decades, it may very well answer a few questions that no one has thought to ask.

Hubble and James Webb Space Telescope Comparison: See the Difference

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