The Mechanics of the Webb Space Telescope: How NASA Unlocked the Next Age of Astronomy

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 get a dim look at one, you have to stare away from fluorescent street lights, flashing billboards, stock market indicators, and other luminous distractors. It’s best to take the train a hundred miles or so north of the state. There, observing the stars no longer required any effort. A breathtaking canopy of sparkle hangs over you, whether you like it or not.

But even from the deepest, darkest, and most remote places, you’ll never see every star with the naked eye. You can’t physically locate all the galaxies, nebulae, exoplanets, and quasars – I can go further – in your line of sight, even with your favorite optical telescope. There are billions and billions (over billions) more cosmic phenomena. It’s just that our human eyes are not built to see the light emitted by them. It’s called infrared light.

Thus, a lot of space treasures are invisible to us. Fortunately, this does not mean that they are outside our scope.

As Stephen Hawking once noted, humans are unique in that we always find a way to transcend our mortal limits. We do it “with our minds and machines”. And sure enough, astronomers over the years have developed fascinating infrared solutions—eventually paving the way for NASA’s James Webb Space Telescope.

Fight against human restraint

Already, big-budget space telescopes like Hubble and Spitzer are clearing up some of the mysteries of cosmic infrared. They contain instruments that scan the sky for elusive light, then translate that information into signals that human pupils can understand. This, in turn, allows us to see a lot of things in the universe that are usually hidden from our eyes.

A group of the faintest galaxies in the universe, seen by the infrared detectors of the Hubble Telescope.

The famous deep field image of the Hubble telescope seen through an infrared detector lens. Those bright spots are not stars. Each one is an entire galaxy.

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

However, if those massive telescopes are the first and second links in the astronomical infrared detection chain, the powerful new agency Web Space Telescope – which released the first set of full images on July 12 – is a brand new season.

Levels beyond Hubble and Spitzer’s infrared capabilities, the JWST was actually built for this task.

Comparison of the vibrant Orion Nebula in infrared and non-infrared views.

Zoom in the image

Comparison of the vibrant Orion Nebula in infrared and non-infrared views.

This image composite compares visible and infrared views of the famous Orion Nebula and its surrounding cloud. The infrared image is from NASA’s Spitzer Space Telescope, and the visible image is from the National Optical Astronomy Observatory, based in Tucson, Arizona.

NASA and others.

The flagship telescope is a $10 billion gold-plated machine stuffed with infrared detectors, fitted with high-tech lenses and programmed with super-powerful software. Its Holy Grail instrument is called the Near Infrared Camera, or Nircam, and it will lead the charge by collecting a wealth of infrared signals in deep space for astronomers to view on Earth.

This is why JWST often holds the promise of revealing an “unfiltered universe”.

Looking through a JWST lens instead of a standard optical telescope would be like looking at the stars from New York’s hypothetical dark region rather than Times Square. There will be countless sparkles either way, even though you are watching the same sky. It’s just that in our dark dark region analogy, we’re seeing extra stars because we’re not constrained by light pollution. On the other hand, JWST collects infrared light in deep space and decodes it for us.

It will point to the exact same universe that Hubble has carefully examined for decades and studied by scientists over the ages, but it will reach the luminosity we can’t see, and possibly reveal hidden space-borne phenomena like violent black holes, alien exoplanets, and a large vortex. Galaxies and…maybe even signals of alien life?

His first pictures have already captured a lot more than our breath. In fact, the NASA employees who were the first to lay their eyes on JWST’s “first light” images said they felt like tears. “What I saw moved me as a scientist, as an engineer, and as a human being,” said Pam Milroy, NASA Deputy Administrator.

Infrared and non-infrared comparison of the Lagoon Nebula.

NASA’s Hubble Space Telescope images compare two diverse views of the swirling core of a vast stellar nursery known as the Lagoon Nebula. On the left is a standard optical version. On the right, infrared.


But before we get into the details of JWST’s infrared mechanics, we have to talk about the electromagnetic spectrum. More specifically, there is a kind of enigma that humans represent to us.

Why don’t we see infrared light?

At some point in your life, you’ve probably wondered what it would be like to see a new color. One indescribable, “green” method really has no definition beyond “caterpillar dye” – or, if you’re a fan of objectivity, “a 550nm wavelength.” After some thought, I bet you’ve settled on the annoying reality that you’ll never know the answer.

That’s because colors are nothing more than the products of light reflected from some sources.

Different colors are dictated by different wavelengths of light, which you can imagine as zigzag zigzags of different dimensions. When we see a blue umbrella, for example, our eyes pick up tighter blue wavelengths that emerge from the waterproof material. While enjoying a fiery sunset, our eyes take in a range of longer, more relaxing red and yellow wavelengths.

All of these wavelengths are neatly regulated on what is known as the “electromagnetic spectrum”. But here’s the problem.

Diagram of the electromagnetic spectrum, showing the areas that Hubble and Webb can see.

This graph shows the electromagnetic energy spectrum, specifically highlighting parts detected by NASA’s Hubble, Spitzer, and Webb space telescopes.

NASA J. Olmsted [STScI]

Although there is an infinite amount of wavelengths of light, humans can “see” only one small part of the spectrum: the visible light region, which encapsulates the colors of the rainbow. It is precisely for this reason that we will never experience the pleasure of watching a color other than the rainbow.

Our bodies won’t allow that to happen, and there’s nothing we can do to change that — except to build a superpower telescope, of course.

Spying on secret wavelengths

Since infrared light bypasses the visible light region, despite its name, it does not appear red. It doesn’t look like anything. In fact, it’s best described as a thermal signature – we can “feel” at infrared wavelengths, which is why a lot of thermal imaging equipment includes infrared detectors. Firefighters, for example, call in the infrared to see where a fire is burning in a building without having to go inside.

But for astronomy specifically, not seeing infrared wavelengths is a big problem.

The universe is expanding. continuously. Which means that as you’re reading this, stars, galaxies and quasars – ultra-luminous objects that act like cosmic lamps – are traveling farther and farther from Earth. And as they do this, the wavelengths of light they give off gradually extend out of our perspective, sort of like pulling on a rubber band. They stretch, recline, and stretch until they turn to the red end of the spectrum. They are “redshifted”.

A reddish view of the center of our Milky Way galaxy, speckled with a huge amount of stars.

The center of the Milky Way is usually hidden from standard optical telescopes due to clouds of dust and gas. But the infrared cameras of the Spitzer Space Telescope managed to penetrate a lot of dust, revealing the stars of the galactic center. The upcoming James Webb Space Telescope could offer an even more spectacular sight – the thrill of fainter stars and sharper details.

NASA, JPL-Caltech, Susan Stolovy (SSC/Caltech), et al.

Take the star born near the beginning of time, for example. At some point, once Earth appeared, this star may have sent wavelengths of blue light toward our young planet. But as it moved further away, in tandem with the expansion of the universe, these wavelengths of blue light began to extend from Earth’s advantage point, becoming redder…redder…and redder.

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

In fact, Nircam said at JWST, “You’ll take a series of images with filters that capture different wavelengths, and use the changes in brightness you detect between these images to estimate the redshift of distant galaxies.”

But ultimately, these wavelengths extend beyond the visible light spectrum. They step into infrared waters – and disappear from our naked eyes. Let us consider the example of this ancient star again.

Now, billions of years later, those reddish wavelengths have slowly moved all the way into the infrared region of the spectrum, from our perspective. The ancient star sends us a kind of starlight that our eyes cannot see.


You can see a picture of all the major Webb tools in this collage. These are not the final full-color “first light” results of the telescope. They only test products.


Stars and Galaxies, Museum of Islamic Art

What this means is that all extremely distant, rare, and possibly information-rich stars and galaxies are invisible to us, along with everything that those stars and galaxies light up. We are missing parts of our universe’s history – the chapters of its beginnings.

But thanks to infrared hunters, JWST’s infrared detectors can show us those missing pieces. They can explain what the universe looked like during its first moments after the Big Bang. They can also find distant exoplanets floating between their outer moons and looking for distant artificial light that may indicate the presence of extraterrestrial life. They will present us with a landscape of the universe clear enough to remind us of our microscopic place in it.


Comparison of the visible and infrared Hubble views of the Monkey Head Nebula. While Hubble has some infrared capabilities, it is nothing compared to Webb.

NASA and the European Space Agency

Plus, to take everything a step further, infrared wavelengths have the added advantage of being long enough to travel through matter, including thick, massive star clouds. Thus, if JWST were to pick up the infrared light emitted by such a cloud, it would be able to paint a picture of the scene within—perhaps, even, a scene of ancient stars being born.

“It is not clear how the universe went from a simpler state of nothing but hydrogen and helium to the universe we see today,” Geithner said. “[T]The Webb Telescope will see great distances into space and an era of time we have never seen before and will help us answer these important questions.”

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

Comparing Hubble and James Webb Space Telescope Images: See the Difference

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