Buzz
As technology advances at a rapid pace, astronomers continue to discover increasingly massive objects in the universe. The title of the 'largest thing in the universe' seems to change almost every year. Some of these cosmic wonders are so immense they leave even the most brilliant scientists in awe, while others defy all logic and shouldn't even exist.
10. The Supervoid
Astronomers have recently found the largest void in the known universe, located in the southern constellation of Eridanus. Stretching across 1.8 billion light-years, this discovery has left scientists perplexed, as they never thought such a vast emptiness could exist.
Even though it's called a 'void,' a void in space is far from empty. It's an area with significantly fewer galaxies than the surrounding regions, in this case, 30 percent less. Voids account for half of the universe, and this fraction is expected to grow as gravity pulls all surrounding matter toward itself. Two key features of this void are its extraordinary size and its connection to the enigmatic WMAP Cold Spot.
This newly discovered supervoid is now considered the most likely cause of the cold spot, a large, seemingly empty area in the cosmic radiation background. Various theories have been proposed to explain the cold spot, including our universe orbiting a universe-sized black hole or a parallel universe pushing against our own. Currently, most scientists lean towards the idea that the cold spot is caused by the supervoid, where protons lose energy and weaken as they travel through it. However, there's still a small chance that the supervoid's position in relation to the cold spot might be coincidental, and further research is needed to confirm whether the void is responsible or if another explanation exists.
9. The Newly Discovered Blob
In 2006, a mysterious blob was dubbed the largest structure in the universe, though this title was soon overtaken by newer findings. This blob is a vast collection of gas, dust, and galaxies, spanning 200 million light-years, and resembles a cluster of green jellyfish. Discovered by Japanese astronomers studying a gas-rich region of the universe, they used a special filter on their telescope, which unexpectedly allowed them to detect the blob.
Each of the blob's three 'arms' is home to galaxies packed at four times the density of the average universe. The galaxies and gas bubbles within the blob are known as Lyman-alpha blobs. These are believed to have originated just two billion years after the Big Bang, a mere instant in the grand timeline of the cosmos. Scientists think they came about when massive stars from the early universe exploded as supernovae and ejected their surrounding gases. Due to the immense size of this structure, astronomers believe it to be one of the earliest formations in the universe. They speculate that, in the far future, even more galaxies will emerge from the gases within the blob.
8. The Shapley Supercluster
For many years, astronomers knew that the Milky Way galaxy was being drawn through the universe at a speed of 2.2 million kilometers per hour toward the Centaurus constellation. They speculated that this movement was due to the presence of a Great Attractor, a mysterious object with a gravitational force powerful enough to pull our galaxy in its direction. However, the exact nature of this object was uncertain because it was located behind the Zone of Avoidance (ZOA), an area of the universe hidden by the Milky Way.
Although traditional astronomy couldn’t penetrate the ZOA, advancements in X-ray astronomy eventually allowed scientists to peer through this barrier and identify the Great Attractor, which turned out to be a massive galaxy cluster. Yet, a problem arose: the Attractor they discovered didn’t have enough gravitational pull to account for the force they were observing. It only explained 44 percent of the total pull. By focusing their telescopes even farther, they found that the source of our galaxy’s cosmic movement was an even larger entity: the Shapley Supercluster.
The Shapley Supercluster is an enormous galaxy cluster situated behind the Great Attractor, drawing both the Attractor and our galaxy toward it. Comprising over 8,000 galaxies with a mass greater than 10 million Suns, this cluster is a gravitational force to be reckoned with. Every galaxy in our region of the universe is heading toward a collision with it.
7. The Great Wall
Similar to other monumental cosmic structures, the Great Wall, or CfA2 Great Wall, was once recognized as the largest known object in the universe. Discovered by American astrophysicists Margaret Joan Geller and John Peter Huchra during a redshift survey for the Harvard-Smithsonian Center for Astrophysics, this vast structure measures about 500 million light-years in length and 16 million light-years in depth, resembling the shape of the Great Wall of China.
However, the precise measurements of the Great Wall remain uncertain. It might extend even further, potentially reaching up to 750 million light-years. The challenge in determining its true size lies in its positioning. Similar to the Shapley Supercluster, the Great Wall is partially hidden by the Zone of Avoidance (ZOA), which makes 20 percent of the observable universe incredibly difficult to study due to the obscuring effects of dust, dense gas in the Milky Way, and the high concentration of stars that block optical wavelengths.
To peer through the ZOA, astronomers must observe the universe using wavelengths that are unaffected by dust, such as infrared surveys, which help penetrate about 10 percent more of the ZOA. Radio surveys can uncover what infrared surveys miss, and near-infrared and X-ray observations can reveal even more, but it's a frustrating challenge for astronomers to study such a vast portion of the universe that's hidden from view. The ZOA creates significant gaps in our understanding of the cosmos.
6. The Laniakea Supercluster
Galaxies naturally tend to cluster together in groups, and regions where these clusters are more densely packed than the average are known as superclusters. In the past, astronomers identified these cosmic formations by their physical locations. However, a recent groundbreaking study has introduced a new way to map the local universe, one that unveils the hidden corners of the cosmos.
This innovative study maps the local universe and its galaxy clusters using gravitational pull rather than physical position. By charting the galaxies' locations, astronomers can infer the gravitational structure of the universe. This new approach is considered more advanced than the old system, as it enables the exploration of regions of the universe that were previously inaccessible to observation. Since it detects the effects of a galaxy's gravity rather than the galaxy itself, it can reveal objects that are otherwise invisible to us.
The study’s results, which pertain solely to our local galaxies, are reshaping our understanding of the local universe. The research team now redefines a supercluster by the extent of its gravitational flow. This new perspective is especially significant for us, as it alters our perceived position in the universe. While the Milky Way was once thought to reside within the Virgo supercluster, the new definition reveals that our region is actually just an arm of the far larger Laniakea supercluster, one of the most colossal objects in the universe. Stretching over 520 million light-years, it represents Earth's new cosmic address.
5. The Sloan Great Wall
The Sloan Great Wall was initially discovered in 2003 by the Sloan Digital Sky Survey, which mapped hundreds of millions of galaxies to uncover the large-scale structure of the universe. This immense galactic ‘filament’ contains multiple superclusters and stretches across the universe like the tentacles of a giant octopus. Measuring 1.4 billion light-years in length, it was once considered the largest structure in the universe.
The Sloan Great Wall itself hasn't been explored as extensively as the superclusters within it, some of which have revealed fascinating features on their own. One of these has a dense core of galaxies with tendrils trailing outwards. Another shows a high level of interaction between its galaxies, including some that are still in the process of merging.
The Wall, and any structure larger than it, has sparked a new mystery regarding the universe. It challenges the cosmological principle, which sets a theoretical limit on the size of universal structures. According to the principle, the universe should exhibit a uniform distribution over large scales, with nothing larger than 1.2 billion light-years existing. Yet, structures like the Sloan Great Wall completely defy this notion.
4. The Huge-LQG
A quasar is a highly energetic region at the core of a galaxy. Driven by supermassive black holes, quasars emit energy at levels 1,000 times greater than anything observed within the entire Milky Way. The Huge-LQG, currently the third-largest structure in the universe, is a cluster of 73 quasars stretched across 4 billion light-years. This vast group of quasars, along with others like it, has been suggested as a precursor to some of the universe’s larger-scale structures, such as the Sloan Great Wall.
The Huge-LQG was discovered by analyzing data from the same survey that identified Sloan's Great Wall. Researchers hypothesized its existence by applying a “friends-of-friends” algorithm, which mapped the density of quasars within a specific region. However, this method is not without its critics, and the existence of this structure remains a subject of ongoing debate.
While some astronomers argue that the Huge-LQG is a real structure, others suggest that the quasars are simply randomly distributed and not part of any coherent larger system. A different researcher examined the Huge-LQG and concluded it to be nothing more than a random arrangement of objects. The debate continues, but evidence is starting to favor the Huge-LQG as a legitimate discovery.
3. The Cosmic Web
Scientists believe that the universe is not randomly arranged. Instead, it’s thought that galaxies are organized into a vast structure of thread-like filaments that connect dense regions, with voids in between. This intricate network is known as the Cosmic Web.
The Cosmic Web is believed to have begun forming very early in the history of the universe. It started from tiny fluctuations in the early universe, which eventually helped shape all of existence. The filaments are especially important, as they are thought to have significantly influenced the universe's evolution. Galaxies within these filaments have a higher rate of star formation and are more likely to interact gravitationally with other galaxies. This process is likely still ongoing. In the filaments, galaxies are essentially prepped and directed toward galaxy clusters, where they eventually meet their end.
Only in recent times have scientists begun to truly understand the Cosmic Web. In a breakthrough, they captured an image of it using radiation from a distant quasar. Quasars are the brightest objects in the universe, and the light from one happened to shine toward a filament, causing the gases to glow. This allowed astronomers to photograph the filaments stretching between galaxies, offering a glimpse of the skeleton of the cosmos.
2. The Hercules-Corona Borealis Great Wall
The largest known structure in the universe today was also discovered while astronomers were scanning for gamma ray bursts. This immense structure, the Hercules-Corona Borealis Wall, spans 10 billion light-years, making it twice the size of the Giant GRB Ring. Since gamma-ray bursts (GRBs) tend to occur in regions with abundant material, astronomers view each burst as a marker of something much larger. When they observed a concentration of GRBs in the direction of the Hercules and Corona Borealis constellations, they deduced that the structure must be a dense collection of galaxy clusters and other matter.
The name Hercules-Corona Borealis Great Wall was actually coined by a teenage Wikipedia contributor from the Philippines. After a Discovery News article mentioned the sky region where the structure was found, a Wikipedia page sprang up, giving it its now-famous name. Although the name is somewhat inaccurate, since the structure spans several other constellations, it gained traction online. This was perhaps the first time that Wikipedia helped name a scientific structure. The Wall’s size, far exceeding the limits proposed by the cosmological principle, has led scientists to reconsider their understanding of the universe’s formation to account for structures like it.
1. The Giant GRB Ring
Stretching an astonishing 5 billion light-years, the Giant GRB Ring is the second-largest structure known to humanity. Its immense size alone is remarkable, but its unusual shape adds an even more fascinating aspect. Astronomers tracking gamma ray bursts—intense energy bursts resulting from massive stars nearing the end of their lifecycle—detected a series of nine similar bursts, each equidistant from Earth. These bursts formed a ring in the sky, spanning over 70 times the size of the full Moon. Given that GRBs are an extremely rare event, the probability of this formation occurring randomly is 1 in 20,000. This led scientists to hypothesize that they had discovered the universe's then-largest structure.
However, the 'ring' we observe is simply a visual perception from Earth. It is believed that the Giant GRB Ring may be a projection of a much larger sphere, within which the gamma ray bursts occurred over a condensed 250 million-year period. This raises the question: what could account for such a vast spherical formation? One possibility suggests that the galaxies within this structure might be gathered around huge concentrations of dark matter, although this remains speculative. At present, researchers have no concrete explanation for the origins of such structures.
