As a New Yorker, I would say that trying to see a star in Times Square is foolish. You have to blink past fluorescent street lights, flashing billboards, stock tickers, and other illuminated distractions to catch even the slightest glimpse. You’re better off taking the train a hundred miles out of state. There, stargazing no longer requires any effort. Whether you like it or not, a breathtaking veil of glitter hangs over you.
But even from the deepest, darkest, most distant place, you will never see every star with the naked eye. You cannot physically find all the galaxies, nebulae, exoplanets, quasars — I could go on — in your line of sight, even with your favorite optical telescope. There are billions upon billions (billions) more cosmic events out there. It’s just that our human eyes are not designed to see the light they emit. This is called infrared light.
So, enough cosmic treasure is invisible to us. Fortunately, however, this does not mean that they are beyond us.
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, over the years astronomers have developed fascinating infrared solutions — eventually paving the way for NASA’s James Webb Space Telescope.
Dealing with human limitation
Already, NASA’s big-budget space telescopes like Hubble and Spitzer are revealing some cosmic infrared mysteries. They contain instruments that scan the sky for elusive light, then convert that data into signals that human pupils can understand. This, in turn, allows us to see many things in the universe that are usually hidden from our eyes.
However, if these large telescopes are the first and second episodes of astronomy’s infrared detection series, the agency’s powerful new Webb Space Telescope — their first full-fledged images will be released on July 12 — is a brand new season.
At levels beyond the infrared capabilities of Hubble and Spitzer, JWST is literally built for the job.
The advanced telescope is a $10 billion machine clad in gold, filled with infrared detectors, accented with high-tech lenses and programmed with ultra-powerful software. His holy grail device is called the Near Infrared Camera, or Nircam, and will handle the payload, collecting a wealth of deep-space infrared signals for astronomers to see on the ground.
That’s why JWST is often said to hold the promise of unlocking the “unfiltered universe.”
Looking through the 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. Even though you’re looking at the same sky, there would be countless more sparkles in either case. Simply put, in our shadowy dark zone analogy, we’re looking at extra stars because light pollution doesn’t get in the way. JWST, on the other hand, collects deep cosmic infrared light and decodes it for us.
It will point to the same universe that Hubble has scrutinized for decades and scientists have studied for centuries, but it will penetrate luminescence we can’t see, possibly revealing hidden space phenomena such as supermassive black holes, exotic exoplanets, giant spirals . galaxies and… maybe even signals of alien life?
For sure, the first glimpses of it are ready to take our breath away. In fact, NASA employees who have already seen JWST’s “first light” images say they were moved to tears. “What I saw moved me as a scientist, an engineer and a person,” said NASA Deputy Administrator Pam Melroy.
But before we get into the specifics of JWST’s infrared mechanics, we need to talk about the electromagnetic spectrum. More specifically, the bit of trouble it creates for us humans.
Why can’t we see infrared light?
At some point in your life, you’ve wondered what it would be like to see a new color. One thing that can’t be described is that “green” doesn’t really have a definition beyond “the color of a caterpillar” — or, if you’re a lens geek, “550 nanometer wavelength.” After some thought, I’m sure you’ve settled on the disturbing reality that you’ll never know the answer.
Because colors are nothing but products of light reflected from some source.
Different colors are dictated by different wavelengths of light, which you can imagine as curved zigzags in different proportions. For example, when we see a blue umbrella, our eyes pick up the denser, bluer wavelengths emitted by the waterproof material. While admiring a fiery sunset, our eyes receive longer, more comfortable red and yellow wavelengths.
All these wavelengths are neatly arranged on what is known as the “electromagnetic spectrum”. But here’s the thing.
Although there are an infinite number of wavelengths of light, humans can only “see” a small part of the spectrum: the region of visible light that includes the colors of the rainbow. This is why we will never have the pleasure of looking at a color that is not a rainbow.
Our bodies won’t allow it, and there’s nothing we can do to change that—except, of course, building a superpower telescope.
Spying on hidden wavelengths
Despite its name, infrared light does not appear red because it falls outside the visible light region. It doesn’t look like anything else. It’s actually better described as a heat signature – we can “sense” infrared wavelengths, which is why many thermal imaging equipment include infrared detectors. Firefighters, for example, call on infrared rays to find out where a fire is burning in a building without going inside.
But especially for astronomy, the invisibility of infrared wavelengths is a major problem.
The universe is expanding. Constantly. This means that as you read this, stars, galaxies and quasars — superluminescent objects that act as cosmic beacons — are moving farther and farther away from Earth. And as they do so, the wavelengths of light they emit slowly stretch out from our perspective, kind of like stretching a rubber band. They stretch and stretch and stretch until they reach the red end of the spectrum. They are “redshifting”.
Take, for example, a star born near the beginning of time. At some point, after Earth’s formation, this star may have emitted waves of blue light toward our young planet. But as it moved away, in tandem with the expansion of the universe, those blue wavelengths of light began to stretch out from Earth’s vantage point, becoming redder…and redder…and redder.
“Redshift is the stretching of light to longer wavelengths that can be used to measure distance,” said Paul Geithner, deputy project manager for JWST.
In fact, he said, JWST’s Nircam will “take a series of images using filters that select different wavelengths and use the brightness changes it detects between these images to estimate the redshifts of distant galaxies.”
Finally, these wavelengths extend beyond the visible light spectrum. They penetrate infrared waters and are invisible to the naked eye. Consider this ancient star example again.
Now, billions of years later, the slowly reddening wavelengths have moved from our perspective into the infrared region of the spectrum. An ancient star sends us starlight that only our eyes can see.
Stars and galaxies, MIA
What this means is that all distant, super-rare, and possibly information-rich stars and galaxies are invisible to us, along with everything else illuminated by those stars and galaxies. We are the missing pieces of our universe’s history — its beginning chapters.
But thanks to infrared hunting tools, JWST’s infrared detectors could show us these missing pieces. They were able to clarify what the cosmos looked like in the first moments after the Big Bang. They could also find distant exoplanets floating among their exomoons and search for distant artificial light that could signal extraterrestrial life. They will give us a picture of the universe that is clear enough to remind us of our microscopic place in it.
Plus, to take things a step further, infrared wavelengths have the added benefit of being long enough to travel through matter, including thick, giant clouds of stardust. So if JWST picks up infrared light from such a cloud, it can capture a picture of the scene inside—perhaps even the scene where ancient stars were born.
“It’s not clear how the universe evolved from a simpler state of nothing but hydrogen and helium to the universe we see today,” Geithner said. “[T]”The Webb telescope will see the far reaches of space and epochs of time that have never been observed before, helping us to answer these important questions.”
But the most desirable aspect of JWST is that, in addition to the questions scientists have been asking for decades, it may very well answer a few questions no one has thought to ask.