NASA — Seeing the Invisible Universe

May 9, 2025

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This computer-simulated image shows a supermassive black hole at the core of a galaxy. The black region in the center represents the black hole’s event horizon, beyond which no light can escape the massive object’s gravitational grip. The black hole’s powerful gravity distorts space around it like a funhouse mirror. Light from background stars is stretched and smeared as it skims by the black hole.

You might wonder — if this Tumblr post is about invisible things, what’s with all the pictures? Even though we can’t see these things with our eyes or even our telescopes, we can still learn about them by studying how they affect their surroundings. Then, we can use what we know to make visualizations that represent our understanding.

When you think of the invisible, you might first picture something fantastical like a magic Ring or Wonder Woman’s airplane, but invisible things surround us every day. Read on to learn about seven of our favorite invisible things in the universe!

1. Black Holes

This short looping animation starts with a white flash as a small white circle, representing a star, gets near a small black circle, representing a black hole. The small white circle is torn apart into billions of small particles that get whipped into an oval coiling around the black hole from the right to the left. One trailing stream is flung in an arc to the left side of the animation while the end closest to the black hole wraps around it in several particle streams. Thousands of flecks from the outermost edge of the streams fly farther away from the black hole as the animation progresses, while the inner stream continues to loop. Two jets of fast-moving white particles burst out of the black hole from the top and bottom. The white speckled outbursts get brighter as the animation concludes. Credit: NASA’s Goddard Space Flight Center/Chris Smith (USRA/GESTAR)

This animation illustrates what happens when an unlucky star strays too close to a monster black hole. Gravitational forces create intense tides that break the star apart into a stream of gas. The trailing part of the stream escapes the system, while the leading part swings back around, surrounding the black hole with a disk of debris. A powerful jet can also form. This cataclysmic phenomenon is called a tidal disruption event.

You know ‘em, and we love ‘em. Black holes are balls of matter packed so tight that their gravity allows nothing — not even light — to escape. Most black holes form when heavy stars collapse under their own weight, crushing their mass to a theoretical singular point of infinite density.

Although they don’t reflect or emit light, we know black holes exist because they influence the environment around them — like tugging on star orbits. Black holes distort space-time, warping the path light travels through, so scientists can also identify black holes by noticing tiny changes in star brightness or position.

2. Dark Matter

In front of a black background, there are millions of glowing green dots. They form a fine, wispy web stretching across the image, like old cobwebs that have collected dust. Over time, more dots collect at the vertices of the web. As the web gets thicker and thicker, the vertices grow and start moving toward each other and toward the center. The smaller dots circle the clumps, like bees buzzing around a hive, until they are pulled inward to join them. Eventually, the clumps merge to create a glowing green mass. The central mass ensnares more dots, coercing even those from the farthest reaches of the screen to circle it. Credit: Simulation: Wu, Hahn, Wechsler, Abel (KIPAC), Visualization: Kaehler (KIPAC)

A simulation of dark matter forming large-scale structure due to gravity.

What do you call something that doesn’t interact with light, has a gravitational pull, and outnumbers all the visible stuff in the universe by five times? Scientists went with “dark matter,” and they think it’s the backbone of our universe’s large-scale structure. We don’t know what dark matter is — we just know it’s nothing we already understand.

We know about dark matter because of its gravitational effects on galaxies and galaxy clusters — observations of how they move tell us there must be something there that we can’t see. Like black holes, we can also see light bend as dark matter’s mass warps space-time.

3. Dark Energy

An animation on a black rectangular background. On the left of the visual is a graph. The y-axis reads “Expansion Speed.” The x-axis is labeled “Time.” At the origin, the x-axis reads, “10 billion years ago.” Halfway across the x-axis is labeled “7 Billion years ago.” At the end of the x-axis is labeled “now.” A line on the graph starts at the top of the y-axis. It slopes down to the right, linearly, as if it were going to draw a straight line from the top left corner of the graph to the bottom right corner of the graph. Around the 7-billion mark, the line begins to decrease in slope very gradually. Three quarters of the way across the x-axis and three quarters of the way down the y-axis, the line reaches a minimum, before quickly curving upward. It rapidly slopes upward, reaching one quarter from the top of the y-axis as it reaches the end of the x-axis labeled “now.” At the same time, on the right hand of the visual is a tiny dark blue sphere which holds within it glowing lighter blue spheres — galaxies and stars — and a lighter blue webbing. As the line crawls across the graph, the sphere expands. At first, its swelling gently slows, corresponding to the decreasing line on the graph. As the line arcs back upward, the sphere expands rapidly until it grows larger than the right half of the image and encroaches on the graph. Credit: NASA's Goddard Space Flight Center

Animation showing a graph of the universe’s expansion over time. While cosmic expansion slowed following the end of inflation, it began picking up the pace around 5 billion years ago. Scientists still aren’t sure why.

No one knows what dark energy is either — just that it’s pushing our universe to expand faster and faster. Some potential theories include an ever-present energy, a defect in the universe’s fabric, or a flaw in our understanding of gravity.

Scientists previously thought that all the universe’s mass would gravitationally attract, slowing its expansion over time. But when they noticed distant galaxies moving away from us faster than expected, researchers knew something was beating gravity on cosmic scales. After further investigation, scientists found traces of dark energy’s influence everywhere — from large-scale structure to the background radiation that permeates the universe.

4. Gravitational Waves

In this animation, two small black circles, representing black holes, orbit one another in a circular counter-clockwise motion. There is a square grid pattern behind them. Around each black hole, a purple haze glows, getting more transparent farther out from the black holes. The haze creates a circle about the size of the black holes’ orbits. Trailing in an arc out from each black hole, an orange hazy strip curls around the frame as the black holes’ orbits circle, like the spiral of a snail shell. The orange strips move farther from the black holes over time, and as they pass over the gridded background, the background warps so that the grid-lines under the stripes appear to bump up. Credit: NASA's Goddard Space Flight Center Conceptual Image Lab

Two black holes orbit each other and generate space-time ripples called gravitational waves in this animation.

Like the ripples in a pond, the most extreme events in the universe — such as black hole mergers — send waves through the fabric of space-time. All moving masses can create gravitational waves, but they are usually so small and weak that we can only detect those caused by massive collisions. Even then they only cause infinitesimal changes in space-time by the time they reach us. Scientists use lasers, like the ground-based LIGO (Laser Interferometer Gravitational-Wave Observatory) to detect this precise change. They also watch pulsar timing, like cosmic clocks, to catch tiny timing differences caused by gravitational waves.

This animation shows gamma rays (magenta), the most energetic form of light, and elusive particles called neutrinos (gray) formed in the jet of an active galaxy far, far away. The emission traveled for about 4 billion years before reaching Earth. On Sept. 22, 2017, the IceCube Neutrino Observatory at the South Pole detected the arrival of a single high-energy neutrino. NASA’s Fermi Gamma-ray Space Telescope showed that the source was a black-hole-powered galaxy named TXS 0506+056, which at the time of the detection was producing the strongest gamma-ray activity Fermi had seen from it in a decade of observations.

5. Neutrinos

This animation shows gamma rays (magenta), the most energetic form of light, and elusive particles called neutrinos (gray) formed in the jet of an active galaxy far, far away. The emission traveled for about 4 billion years before reaching Earth. On Sept. 22, 2017, the IceCube Neutrino Observatory at the South Pole detected the arrival of a single high-energy neutrino. NASA’s Fermi Gamma-ray Space Telescope showed that the source was a black-hole-powered galaxy named TXS 0506+056, which at the time of the detection was producing the strongest gamma-ray activity Fermi had seen from it in a decade of observations.

Because only gravity and the weak force affect neutrinos, they don’t easily interact with other matter — hundreds of trillions of these tiny, uncharged particles pass through you every second! Neutrinos come from unstable atom decay all around us, from nuclear reactions in the Sun to exploding stars, black holes, and even bananas.

Scientists theoretically predicted neutrinos, but we know they actually exist because, like black holes, they sometimes influence their surroundings. The National Science Foundation’s IceCube Neutrino Observatory detects when neutrinos interact with other subatomic particles in ice via the weak force.

6. Cosmic Rays

Earth’s horizon from space divides this animation in half from the top-left corner to the bottom-right corner. The slightly curved surface glows faintly white into the inky black space that takes up the other half of the frame. Earth is primarily blue, covered in soft patchy white clouds that glow soft yellow. Hundreds of small white streaks rain down diagonally from the right toward Earth. As they reach the faint white glow, they suddenly break into thousands of smaller particles that shower down onto the planet. Credit: NASA's Goddard Space Flight Center

This animation illustrates cosmic ray particles striking Earth’s atmosphere and creating showers of particles.

Every day, trillions of cosmic rays pelt Earth’s atmosphere, careening in at nearly light-speed — mostly from outside our solar system. Magnetic fields knock these tiny charged particles around space until we can hardly tell where they came from, but we think high energy events like supernovae can accelerate them. Earth’s atmosphere and magnetic field protect us from cosmic rays, meaning few actually make it to the ground.

Though we don’t see the cosmic rays that make it to the ground, they tamper with equipment, showing up as radiation or as “bright” dots that come and go between pictures on some digital cameras. Cosmic rays can harm astronauts in space, so there are plenty of precautions to protect and monitor them.

7. (Most) Electromagnetic Radiation

A diagram reading “electromagnetic spectrum.” The diagram consists primarily of a rectangle that stretches across the width of the image. The rectangle is broken into six sections labelled left to right, “gamma,” then “x-ray,” then “ultraviolet,” then “visible,” then “infrared,” then “microwave,” and finally “radio.” The sections are not all the same size, with visible being the smallest by far, then gamma ray, then x-ray, then ultraviolet, microwave, radio, and finally infrared being the longest section. The individual sections are divided further into five sections that create color gradients. Gamma, x-ray, and microwave are gradients of grey. Ultraviolet is a gradient from a pinkish purple on the left to purple on the right. Infrared is a gradient from red on the left to orange on the right. The visible section creates a rainbow, going from purple, to blue, green, yellow, and finally red. Above each section is a squiggly vertical line. Each section has squiggly lines taking up the same vertical space but they have larger and larger curves going from left to right, with gamma having the smallest amplitude and wavelength and radio having the largest. Credit: NASA, ESA, CSA, Joseph Olmsted (STScI)

The electromagnetic spectrum is the name we use when we talk about different types of light as a group. The parts of the electromagnetic spectrum, arranged from highest to lowest energy are: gamma rays, X-rays, ultraviolet light, visible light, infrared light, microwaves, and radio waves. All the parts of the electromagnetic spectrum are the same thing — radiation. Radiation is made up of a stream of photons — particles without mass that move in a wave pattern all at the same speed, the speed of light. Each photon contains a certain amount of energy.

The light that we see is a small slice of the electromagnetic spectrum, which spans many wavelengths. We frequently use different wavelengths of light — from radios to airport security scanners and telescopes.

Visible light makes it possible for many of us to perceive the universe every day, but this range of light is just 0.0035 percent of the entire spectrum. With this in mind, it seems that we live in a universe that’s more invisible than not! NASA missions like NASA’s Fermi, James Webb, and Nancy Grace Roman space telescopes will continue to uncloak the cosmos and answer some of science’s most mysterious questions.

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