You’ve seen the images. Swirling neon purples, deep velvety blacks, and those piercing gold diffraction spikes that make every star look like a diamond. Since the James Webb Space Telescope (JWST) started beaming data back in 2022, our social media feeds have been plastered with what we call a picture of a universe. But here is the thing that hits most people like a cold bucket of water: if you were floating out there in the Pillars of Creation, you wouldn't see any of that.
The universe is mostly invisible to us.
Human eyes are remarkably limited. We see a tiny sliver of the electromagnetic spectrum. To get a real picture of a universe, scientists have to act more like translators than photographers. They take wavelengths of light that would be totally invisible to your naked eye—infrared, X-ray, radio—and they "shift" them into colors you can actually perceive. It isn’t "fake," per se. It’s more like a map. You wouldn’t say a topographical map is lying because the mountains aren't actually bright green and the valleys aren't actually brown, right? It’s data visualization.
The Hubble vs. Webb Paradigm Shift
For decades, the Hubble Space Telescope was the gold standard. Hubble mostly looks at visible light, which is why its photos felt so "real." But then Webb came along with its massive gold-plated honeycombs. Webb doesn’t care about visible light. It’s an infrared beast.
Why infrared? Because the universe is expanding.
As light travels from the very first stars across billions of light-years, the space it travels through literally stretches. This stretches the light waves too. A blue photon from 13 billion years ago gets stretched out so far that by the time it reaches Earth, it’s shifted all the way into the infrared. If you tried to take a picture of a universe using only visible light to see the beginning of time, you’d see a whole lot of nothing. It would be pitch black.
Webb peers through the dust. That's its superpower. Hubble’s famous "Pillars of Creation" looks like solid, towering clouds of gas. In Webb’s infrared version, those clouds become semi-transparent. You can see the baby stars screaming to life inside the cocoons of gas. It’s a different way of seeing reality.
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How NASA Chooses the Colors
When Joe DePasquale or Alyssa Pagan—the lead imaging developers at the Space Telescope Science Institute—get the raw data from a telescope, it looks like a grainy, black-and-white mess. It’s basically just a spreadsheet of numbers representing photon counts.
They use a process called "chromatic ordering."
Basically, they assign the shortest wavelength of light to blue, the middle to green, and the longest to red. It’s a logical hierarchy. By layering these "colored" data sets on top of each other, a masterpiece emerges. But there is a lot of artistry involved. They have to balance the contrast so the bright stars don't wash out the faint nebulosity. They have to decide which features to emphasize.
If they want to show off the ionized oxygen in a nebula, they might lean into the blues. If they want to highlight the cool molecular hydrogen, they go for the reds. Every picture of a universe you see is an editorial choice made by a human being to highlight specific scientific truths.
The Weird Reality of the "Deep Field"
In 1995, Robert Williams, who was the director of the Space Telescope Science Institute, did something people thought was insane. He pointed Hubble at a tiny, empty patch of sky near the Big Dipper. It was a spot about the size of a grain of rice held at arm's length. There was nothing there. Just blackness.
He stared at that nothingness for ten days.
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When the data came back, it changed everything. That "empty" spot contained over 3,000 galaxies. Each galaxy had billions of stars. This became the Hubble Deep Field. It was the first time we got a true picture of a universe that showed just how crowded the cosmos really is.
Fast forward to the JWST First Deep Field (SMACS 0723). What took Hubble weeks took Webb just 12.5 hours. And because Webb is so much more sensitive, it showed us "gravitational lensing." You’ll see these weird, warped, stretched-out arcs of light in the photo. That’s actually a massive cluster of galaxies in the foreground acting like a giant magnifying glass. Its gravity is so intense it literally bends the light of the galaxies behind it.
Why Don't We Have a Photo of the Whole Thing?
You might wonder why we can’t just zoom out and take a single picture of a universe from the outside.
Well, because there is no "outside."
We are inside the fishbowl. Plus, light has a speed limit. When we look further away, we are looking back in time. If we look far enough, we hit a wall called the Cosmic Microwave Background (CMB). This is the "afterglow" of the Big Bang. It’s the oldest picture of a universe possible, dating back to about 380,000 years after the start of everything. Before that, the universe was a hot, dense soup of plasma that light couldn't travel through. It was opaque.
So, our "picture" of the entire universe is actually a sphere of light with us at the center. It’s called the Observable Universe. Anything beyond that sphere is moving away from us faster than the speed of light due to the expansion of space. We will never see it. It’s gone forever.
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The Mystery of Dark Matter
Here is a fun fact to ruin your night: everything we see in a picture of a universe—all the stars, planets, nebulas, and black holes—only accounts for about 5% of what’s actually out there.
The rest is Dark Matter and Dark Energy.
We can’t see them. We can’t touch them. We only know they exist because of how their gravity tugs on the stuff we can see. When you look at a beautiful photo of a spiral galaxy, you’re only looking at the "foam" on top of a very deep, very dark ocean. Scientists are currently using "weak lensing" maps to try and create a picture of a universe that includes this dark matter, but it looks more like a spiderweb of invisible threads than a pretty galaxy.
How to Read a Space Image Like a Pro
Next time you scroll past a stunning space photo, don't just go "ooh, pretty." Look for the clues.
- Check the diffraction spikes. If the stars have six big points and two small ones, that’s a Webb photo. It’s caused by the shape of the hexagonal mirrors and the struts holding the secondary mirror. Hubble’s stars usually have four points.
- Look for the "Redshift." The reddest, tiniest dots in a deep field are usually the oldest things in the photo. They are red because they are moving away from us so fast.
- Ignore the "noise." Space isn't actually that colorful to the eye. If you see bright neon greens, that’s usually a specific filter used to show oxygen or sulfur.
Honestly, the fact that we can even produce a picture of a universe is a miracle of engineering. We are using mirrors made of beryllium and coated in a layer of gold only a few hundred atoms thick, sitting a million miles away from Earth at a spot called L2, cooled to nearly absolute zero so its own heat doesn't interfere with the infrared sensors.
It’s a lot of work for a wallpaper.
Actionable Steps for Aspiring Stargazers
If this has sparked an itch to see more than just the "Photoshopped" versions of space, you can actually get involved.
- Access Raw Data: You don’t need to be a NASA scientist to look at these files. The Mikulski Archive for Space Telescopes (MAST) is public. You can download the same FITS files the pros use and try your hand at processing them using software like FITS Liberator or PixInsight.
- Citizen Science: Join projects like Zooniverse. They often need "human eyes" to help classify galaxy shapes or find exoplanets in data sets that AI still struggles with.
- Check the Metadata: Whenever you see a new picture of a universe on the NASA or ESA websites, scroll down to the "Fast Facts" or "About the Image" section. They will explicitly tell you which filters (like F187N or F444W) were used and what colors they were assigned.
- Compare Wavelengths: Use tools like ESASky to toggle between X-ray, Infrared, and Visible light for the same object. It will completely change how you perceive the structure of the cosmos.
Understanding that these images are "constructed" doesn't make them less beautiful. If anything, it makes them more impressive. We aren't just looking at pretty lights; we are looking at a translated map of the history of existence.