Buzz
As Douglas Adams, the cherished author of 'The Hitchhiker's Guide to the Galaxy,' once famously said: 'Space is big. You just won’t believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space.' These words ring truer than ever because the universe is so vast that its sheer scale is beyond human comprehension, even for those with the deepest knowledge and open minds. With a diameter of over 93 billion light-years, the universe holds many gigantic objects, just waiting to be discovered. This list compiles some of the most immense and fascinating structures in space, many of which consist of a collection of celestial bodies held together by the immense force of gravity. Since space is so expansive, traditional Earth-based methods of measuring distances fall short, so we will use light-years as our unit of measurement — the distance that light travels in one year.
Light moves at a speed of 186,000 miles (300,000 kilometers) per second, which translates to 5,878,000,000,000 miles (9,461,000,000,000 kilometers) annually. At this pace, it would take light over 4 years to reach the Alpha Centauri system, which is the closest stellar neighbor to our sun. The Milky Way galaxy, which is immense, would take light more than 100,000 years to cross from one side to the other.
We hope you enjoy this brief journey into the vast expanse of the universe.
10. Swift J1357.2
We begin this list with the closest structure to Earth (and the only one located within our galaxy), officially named Swift J1357.2. This remarkable structure resides almost 5,000 light-years away in the Virgo constellation. It remains one of the most puzzling objects on the list, though physicists speculate that it consists of a binary system with a star and a stellar-mass black hole. The companion star orbits the system's center of mass in the shortest known orbital period—just 2.8 hours.
Contrary to popular belief, black holes aren’t cosmic vacuum cleaners that suck in everything around them. Instead, they only consume matter that comes too close (within the so-called “event horizon,” the point where nothing, not even light, can escape). Gravitational disturbances can cause objects in stable orbits to veer off course and spiral inward. This leads to an accumulation of more material than the black hole can absorb at any one time, forming what is known as an accretion disk.
Swift J1357.2 likely has a structure similar to that of an accretion disk. However, unlike typical disks, this one has formed in the outermost layer and behaves like a wave, traveling vertically outward rather than horizontally. This results in a periodic “dimming” of the companion star every few seconds.
9. Hanny’s Voorwerp
At the top of this image (linked below for those who determine which lists get published) is IC 297, a spiral galaxy situated about 650 million light-years from Earth in the Leo Minor constellation.
Positioned just below the galaxy (though separated by thousands of light-years in reality) is Hanny’s Voorwerp — one of the most peculiar structures known to exist. And that’s saying a lot, considering how many bizarre discoveries Hubble (and other cutting-edge telescopes) have revealed. Not only is it strange, but this structure is also incredibly massive, with a diameter surpassing that of the Milky Way itself (more than 100,000 light-years).
The most probable origin of this structure is a quasar that once resided at the center of IC 297. Long ago, the quasar expelled the eerie green material that eventually twisted into filaments, forming this distinct structure.
8. The Horologium-Reticulum Supercluster
This colossal structure, home to over 350,000 individual galaxies (including 30,000 large galaxies, 5,000 galaxy groups, and more than 300,000 dwarf galaxies), is located around 700 million light-years from Earth, at least in the nearest portion. It's so immense that we're uncertain of its farthest reach, but it’s thought to extend at least 1.2 billion light-years away, spanning more than 550 million light-years in total.
Within the Horologium-Reticulum Supercluster lies Abell 3266, one of the largest regions in our local universe. Moreover, a massive cloud of gas, stretching more than 5 million light-years, is rapidly heading toward the cluster, which will trigger a new wave of star formation in the galaxies it affects.
7. The Newfound Blob
The 'Newfound Blob' is not only one of the largest structures in the universe, but also one of the oldest and most distant. At one point, it was considered the largest structure, until modern astronomy advanced and the development of powerful telescopes allowed us to peer back to the beginning of time itself.
The Newfound Blob consists of massive gas bubbles, with several galaxies scattered within, and these are referred to as 'Lyman Alpha Blobs' (an inventive name, indeed!). The largest known blob of this kind is situated approximately 11 billion light-years away from Earth and spans over 200 million light-years. Some of its individual gas bubbles measure 400,000 light-years across, four times the size of our entire galaxy!
Given its enormous distance, the blob formed just 2 billion years after the Big Bang. Taking into account the universe's accelerating expansion, it's safe to assume that the blob is now much farther from where it originally existed when the light first left the region, beginning its journey to our planet.
6. The Great Attractor
What would a list about space be without a touch of mystery? This entry surely delivers, as it’s the ultimate enigma in the realm of unsolved cosmological puzzles.
While studying one of the nearest super-clusters to us, the Norma Cluster (about 220 million light-years away), astronomers stumbled upon something odd and genuinely puzzling. A force, dubbed “the Great Attractor,” appears to be gravitationally pulling galaxies in the region toward it, at speeds surpassing 200,000 miles per hour.
The mass required for this structure (or object, though it’s unlikely to be a single entity) to exert such a force on the galaxies is colossal, which leads some astronomers to suggest that dark energy, the force driving the expansion of the universe, could be responsible. Alternatively, this could imply that we are missing vital factors needed to understand how gravity operates on a grand scale. (Or, perhaps, this is where all the missing socks go.)
5. The Sloane Great Wall of Galaxies
When observing the vastness of the universe, we notice that many galaxies (each typically containing billions of stars) tend to cluster together, forming galaxy groups. These clusters, in turn, are separated by immense voids. These structures are known as ‘filaments,’ and there are quite a few of them. Among them, one of the most massive is known as “The Sloane Great Wall.” This immense structure stretches over 1.38 billion light-years and is located roughly one billion light-years from Earth. Its length is particularly astonishing, as it makes up almost 1/60th (about 5%) of the observable universe’s diameter. (Note that this is only the portion we can detect— the actual universe is far larger.)
Even more fascinating is that this region defies the very foundation of modern cosmology, which assumes the universe is only 13.7 billion years old. Many renowned physicists argue that such a massive structure would require between 100 billion and 150 billion years to fully form. To put it in perspective, if the entire Earth took just one week to form, the Great Wall would take more than two quintillion years to develop. Clearly, it’s an unfathomably vast structure.
4. The Eridanus Supervoid
We often think of space as empty. And for the most part, it is — over 99% of the universe is void. However, this does not account for the emptiness of matter itself (as atoms, for instance, are mostly empty space). With the rise of quantum physics, we now understand that even 'empty' space is not truly vacant, but rather contains trace amounts of gas, energy, and virtual particles that briefly come into existence before disappearing again.
Thus, it’s quite surprising to encounter regions of space that are almost entirely devoid of all matter, including stars, planets, galaxies, clusters, interstellar material, and even dark matter (the elusive substance that makes up a large part of the universe’s mass, despite being invisible). The largest of these voids can be found in the Eridanus constellation. Spanning a mind-boggling one billion light-years, this void has intrigued physicists, who have proposed various theories regarding its origin. Some speculate that it is a remnant from a parallel universe that once interacted with our own, while others suggest it could be the core of a universe-sized black hole.
3. The Actual Universe
First and foremost, I must emphasize that the true size of the universe remains an enigma. While many physicists argue that the universe could be infinite (and that’s before even considering the possibility of a multiverse with endless other universes), the actual size hinges on the fundamental shape of spacetime itself. Nonetheless, one thing we do know is that the observable universe is at least 14 trillion light-years in diameter, excluding speculative factors. To put this in perspective, multiply the estimated number of stars in each galaxy by the estimated number of galaxies in the universe, and you’ll begin to approach a rough estimate of the universe's potential star count. These numbers extend into the septillions, depending on your source.
Let’s break that down in simpler terms:
Atoms themselves are largely empty space, with roughly 99% of their volume being vacant, leaving behind a minuscule nucleus. When compared to the universe, some estimates suggest that the true size of the universe could be ten BILLION times larger than an atom’s nucleus when comparing it to the observable universe as the nucleus, and the universe itself as the entire atom.
Here’s the strange part: because the universe is expanding (as I mentioned earlier), in the far-off future, the observable universe will begin to contract, eventually freezing and fading out of our sight forever. Any light emitted from galaxies beyond the so-called 'light horizon' (or the Hubble Volume, as some call it) will never reach us, as the light will be traveling too fast and too far to make it.
So, yes. Even though the universe is still growing, it will eventually begin to shrink. (At least, that’s what it will seem like to those of us still around.) The night sky will become dark, empty, and devoid of all its defining features. But don’t panic. Long before that happens, our sun will transition into a red giant, consuming Earth and anyone unfortunate enough to still be here. Enjoy the present while it lasts!
2. The Observable Universe
Now, let’s dive into the truly fascinating and complex part of our journey. The universe is essentially split into two main sections: the observable universe and the actual universe. Both of these are undeniable structures, with their filaments and voids clearly interconnected.
We’re faced with limitations imposed by the laws of physics when it comes to observing the universe. As we know, light typically travels at a constant speed as it moves through the vacuum of space. This means we cannot observe light from any object beyond the 'light horizon'—a boundary within space where light can actually reach us. This horizon has a radius of 13.7 BILLION light-years, which happens to be the same as the universe’s age. Its total diameter stretches an incredible 93 billion light-years. This is made possible by the rapid expansion of the universe just after the big bang, when it was just a fraction of a second old. This rapid expansion, known as 'inflation,' continues today, albeit at a much slower pace.
In essence: The observable universe is home to an estimated 10 million super-clusters (a few of which we’ve touched upon today), 350 billion large galaxies like our Milky Way, 25 billion galaxy groups, 7 trillion dwarf galaxies (also called satellite galaxies), and a staggering 30 billion trillion stars.
And that leads us to the final entry on our list:
1. Large Quasar Group
Now, we turn to the Large Quasar Group (LQG), the largest known structure in the universe. This vast region spans over a billion light-years and houses more than 73 active quasars—luminous objects typically found surrounding supermassive black holes. Some quasars emit more light and energy in a fraction of a second than all the stars in our galaxy combined! This relatively recent discovery not only showcases a mind-blowing scale but also challenges a key scientific idea known as the 'cosmological principle.' This principle suggests that, on a large scale, the universe should appear the same everywhere we look.
The sheer size of this structure (and its unparalleled dimensions) creates a problem for the cosmological principle. It’s far from the only discovery that has shaken our understanding and reminds us how much we still have to learn about the cosmos.
