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Tuesday, August 9, 2022

Webb Space Telescope Mechanics: How NASA Unlocked Astronomy’s Next Great Era

As a New Yorker, I’d say trying to spot a star from Times Square is little more than a fool’s errand. 

To catch even the faintest glimpse of one, you’d have to squint past fluorescent street lamps, flashing billboards, stock market tickers and other illuminated distractions. You’re better off taking the train a hundred or so miles upstate. Out there, stargazing no longer requires any effort. A breathtaking canopy of sparkles hangs over you, whether you like it or not. 

But even from the deepest, darkest, most remote location, you will never see every star with your naked eye. You physically can’t spot all the galaxies, nebulae, exoplanets, quasars — I could go on — in your line of vision, even with your favorite off-the-shelf optical telescope. There are billions upon billions (upon billions) more cosmic phenomena out there. It’s just our human eyes aren’t built to see the light they emanate. It’s called infrared light.

Thus, quite a lot of space treasures are invisible to us. Fortunately, however, that doesn’t mean they’re beyond us. 

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

Fighting a human restriction

Already, big-budget space telescopes like NASA’s Hubble and Spitzer elucidate some cosmic infrared secrets. They contain instruments that sky-scan for the elusive light, then translate that information into signals comprehensible by human pupils. This, in turn, allows us to see lots of stuff in the universe that’s normally hidden to our eyes. 

A bunch of our universe's faintest galaxies, seen with Hubble's infrared detectors.

Hubble’s famous deep field image seen through the lens of infrared detection. Those bright spots aren’t stars. Each one is an entire galaxy.

NASA, ESA, and R. Thompson (Univ. Arizona)

However, if those massive telescopes are episode one and two of astronomy’s infrared detection series, the agency’s powerful new Webb Space Telescope — of which the first set of full-fledged images was released on July 12 — is an entirely new season.

Levels beyond the Hubble and Spitzer’s infrared capabilities, the JWST is literally built for the job. 

A comparison of the vivid Orion nebula in infrared and non-infrared views.


Enlarge Image

A comparison of the vivid Orion nebula in infrared and non-infrared views.

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

NASA et al.

The trailblazing telescope is a gold-plated, $10 billion machine stuffed with infrared detectors, accented with high-tech lenses and programmed with ultrapowerful software. Its holy grail device is called the Near Infrared Camera, or Nircam, and will lead the charge by collecting a wealth of deep space infrared signals for astronomers to view on the ground. 

This is why the JWST is often said to hold the promise of unveiling an “unfiltered universe.”

Looking through the JWST lens instead of a standard optical telescope would be like looking up at the stars from my hypothetical New York dark zone instead of Times Square. There’d be a myriad more sparkles in both cases, even though you’re viewing the same sky. It’s just that in our shadowy dark zone analogy, we’re viewing extra stars because we’re uninhibited by light pollution. The JWST, on the other hand, is collecting deep space infrared light and decoding it for us.

It will point at the exact same universe that the Hubble has scrutinized for decades and scientists have studied for ages, but it will access luminescence we can’t see, possibly revealing concealed space-borne phenomena like violent black holes, exotic exoplanets, grand spiral galaxies and… maybe even signals of alien life? 

Its first images have already taken much more than our breath away. In fact, NASA personnel who were the first to lay eyes on the JWST’s “first light” images said they were moved to tears. “What I have seen moved me, as a scientist, as an engineer and as a human being,” Pam Melroy, NASA’s deputy administrator, said. 

A infrared and non-infrared comparison of the Lagoon Nebula.

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

NASA, ESA, and STScI

But before we get into the specifics of the JWST’s infrared mechanics, we have to talk about the electromagnetic spectrum. More specifically, a bit of a conundrum that it poses for us humans. 

Why can’t we see infrared light?

At some point in your life, you might’ve wondered what it’d be like to see a new color. One that can’t be described, the way “green” doesn’t really have a definition beyond “the hue of a caterpillar,” — or, if you’re an objectivity fan, “a wavelength of 550 nanometers.” After some thought, I’d bet you settled into the disturbing reality that you’ll never know the answer. 

It’s because colors are nothing more than the products of light reflecting off some source. 

Different colors are dictated by different wavelengths of light, which you can imagine as curvy zigzags of various proportions. When we see a blue umbrella, for instance, our eyes pick up on tighter, blue wavelengths emanating from the waterproof material. While admiring a fiery sunset, our eyes take in a bunch of longer, more relaxed red and yellow wavelengths. 

All these wavelengths are neatly organized on what’s known as “the electromagnetic spectrum.” But here’s the issue. 

A diagram of the electromagnetic spectrum, showing what regions Hubble and Webb can see.

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

NASA and J. Olmsted [STScI]

Though there’s an infinite amount of light wavelengths, humans can only “see” one tiny part of the spectrum: The visible light region, which encapsulates the colors of the rainbow. That’s precisely why we’ll never experience the pleasure of viewing a non-rainbow color. 

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

Spying on secret wavelengths

Because infrared light falls beyond the visible light region, despite its name, it doesn’t look red. It doesn’t look like anything. It’s actually better described as a heat signature — we can “feel” infrared wavelengths, which is why a lot of thermal imaging equipment includes infrared detectors. Firefighters, for example, call on infrared to learn where a fire may be burning in a building without having to go inside. 

But specifically to astronomy, the non-visibility of infrared wavelengths is a major problem.

The universe is expanding. Constantly. Which means that, as you read this, stars, galaxies and quasars — super luminescent objects that act like cosmic flashlights — are traveling farther and farther from Earth. And as they do that, the wavelengths of light they give off gradually stretch out from our perspective, sort of like a rubber band being pulled. They extend, recline and stretch until they shift to the red end of the spectrum. They “redshift.” 

A reddish view of our Milky Way's center, speckled by a huge amount of stars.

Our Milky Way’s center is normally hidden from standard, 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 of the crowded galactic center. The upcoming James Webb Space Telescope can offer a view even more spectacular than this — teasing out fainter stars and sharper details.

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

Take a star that was born near the beginning of time, for instance. At some point, once Earth came into existence, this star might have radiated blue light wavelengths toward our young planet. But as it got farther away, in tandem with the universe’s expansion, those blue light wavelengths started to stretch from Earth’s vantage point, getting redder… and redder… and redder. 

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

In fact, he said the JWST’s Nircam, “will take a series of pictures using filters that pick up different wavelengths, and use the changes in brightness it detects between these images to estimate the redshifts of the distant galaxies.” 

Eventually, however, these wavelengths stretch even beyond the visible light spectrum. They tread into infrared waters — and they disappear from the view of our naked eye. Consider that ancient star example again. 

Now, billions of years later, those slowly reddening wavelengths have moved all the way into the infrared region of the spectrum, from our perspective. The ancient star is only sending us the kind of starlight our eyes can’t see.

webb-img-sharpness-1200x635.png

You can see an image from all of Webb’s major instruments in this collage. These aren’t the telescope’s final, full-color “first light” results. They’re just testing products.

NASA/STScI

Stars and galaxies, MIA

What this means is that all the distant, super rare and probably information-rich stars and galaxies are invisible to us, along with everything illuminated by those stars and galaxies. We’re missing the pieces of our universe’s history — its beginning chapters. 

But thanks to its infrared-hunting instruments, the JWST’s infrared detectors could show us those missing pieces. They could elucidate what the cosmos looked like during its first moments after the Big Bang. They could also find distant exoplanets floating among their own exomoons and search for far away artificial light that may signal extraterrestrial life. They will offer us a landscape of the universe that’s clear enough to remind us of our microscopic place in it. 

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A comparison of Hubble’s visible and infrared views of the Monkey Head Nebula. While the Hubble has some infrared capabilities, it’s nothing compared to the Webb.

NASA and ESA

Plus, to take everything a step further, infrared wavelengths have the added benefit of being long enough to travel through matter, including thick, enormous stardust clouds. Thus, if the JWST picks up on infrared light radiating from such a cloud, it’d 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 transformed from a simpler state of nothing but hydrogen and helium to the universe we see today,” Geithner said. “[T]he Webb telescope will see distant reaches of space and an epoch of time never observed before and help us answer these important questions.”

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

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

See all photos

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