Our vast Universe contains galaxies grouped into clusters, clusters grouped into superclusters, and superclusters grouped into the cosmic web. But how many superclusters are there in our observable Universe? This is a question that has fascinated astronomers who seek to understand the large-scale structure of the cosmos.
In this article, we will explore what superclusters are, how they formed after the Big Bang, and review what various surveys have revealed about the number of superclusters that can currently be observed from Earth.
We will look at the different approaches used to identify and categorize these immense structures of galaxies and dark matter. Although estimates vary, one thing is clear – our Universe is filled with a vast cosmic web of incomprehensible scale woven from thousands upon thousands of superclusters.
How Many Superclusters Are There?
It is estimated that there are around 10 million superclusters observable from the Earth, but the exact number of superclusters in the Universe remains uncertain.
However, astronomers have identified several prominent superclusters, such as the Shapley Supercluster and the Laniakea Supercluster, which houses our own Milky Way.
Ongoing astronomical observations and studies contribute to the continuous identification of new superclusters.
Definition of a Supercluster
A supercluster is a massive grouping of galaxies bound together by gravity. They represent the largest known structures in the Universe, often containing tens of thousands of galaxies spanning hundreds of millions of light-years.
Spanning hundreds of millions of light-years, superclusters are bound together by gravity, influencing the large-scale structure of the Universe and contributing to its dynamic evolution. These vast arrangements of galaxies play a pivotal role in shaping the distribution of matter and influencing the expansion of the Universe.
Superclusters have three defining characteristics– scale and size, gravity binding, and influence on cosmic expansion.
Types of superclusters
There are two main types of superclusters. Rich superclusters contain a very high density of galaxies, while poor superclusters are more spread out. Our own Local Supercluster containing the Milky Way is an example of a poor supercluster.
In contrast, the Shapley Supercluster and Saraswati Supercluster are incredibly dense, rich superclusters. The Shapley Supercluster is one of the most massive superclusters, containing over 8,000 galaxies.
Formation of Superclusters
The leading theory holds that superclusters formed early in the Universe from small perturbations or “ripples” in the density of matter shortly after the Big Bang. As the Universe expanded, denser regions could attract more matter through gravity.
This led to localized clumping of matter on enormous scales. The localized clumping eventually formed the immense structures known as superclusters.
Superclusters continue to slowly evolve and merge over billions of years as the collective gravity of their galaxies and dark matter pulls them together.
Observable Universe and Dark Matter
The cosmic expanse
The observable Universe is vast. It spans 92 billion light-years and contains billions of galaxies. The observable Universe represents the part we can see, giving a glimpse into the larger cosmos.
The observable Universe holds many mysteries but reveals little about the Universe’s full extent. Its origins and ultimate fate remain unknown.
Dark matter’s influence
Dark matter is a mysterious and invisible substance that makes up about 27% of the Universe’s total mass and energy. It doesn’t emit, absorb, or reflect light, making it undetectable through electromagnetic radiation. Its presence is inferred through its gravitational effects on visible matter.
Dark matter forms a cosmic web. Galaxies and galaxy clusters lie along its filaments. Dark matter drives the growth of cosmic structure. It draws normal matter into clumps and clusters.
How Does Dark Matter Affect Superclusters?
Dark matter profoundly influences the formation and dynamics of superclusters, which are some of the largest known structures in the Universe. Superclusters are massive agglomerations of galaxy clusters and groups that are gravitationally bound together on a cosmic scale. Here’s how dark matter affects superclusters:
Gravitational interplay
Dark matter is the gravitational “glue” that initiates and drives the formation of superclusters. As the Universe evolves, dark matter attracts both visible matter (such as galaxies and gas) and other dark matter towards overdense regions. Over time, this gravitational attraction leads to the formation of large-scale structures, including superclusters. Within superclusters, dark matter shapes motions, and its gravity pulls galaxies into coherent flows. This gives superclusters form and structure.
Structural support
Dark matter provides the majority of the mass in superclusters, even though it is invisible. Its gravitational pull is essential for holding the entire structure together against the expansive force of the Universe’s accelerated expansion driven by dark energy.
Galactic filaments and voids
Dark matter forms a cosmic web of interconnected filaments, creating a large-scale structure that includes superclusters. Galactic filaments, which are dense regions of dark matter and gas, serve as the backbone of the cosmic web, connecting clusters of galaxies within superclusters.
Surrounding these filaments are vast cosmic voids, regions with lower concentrations of matter, including dark matter. The contrast between these voids and the denser regions contributes to the overall structure and dynamics of superclusters.
Large-Scale Structures of the Universe
Large-scale structures in the Universe refer to the vast, organized patterns of matter on scales much larger than individual galaxies. These structures are the result of gravitational interactions and the evolution of cosmic structures over billions of years.
The largest structures form a cosmic web that’s intricate in design. Its voids are shaped by dark energy’s repulsion and the voids of empty space separate the web’s strands. This web stretches for billions of light-years.
The web emerged from fluctuations after the Big Bang. Denser regions drew more matter as the Universe expanded, which helped build the cosmic structure.
This web represents the Universe’s fundamental architecture. Its patterns reflect forces during cosmic evolution. The truth is that the web still evolves over cosmic time.
Milky Way Galaxy and Clusters of Galaxies
Localized perspective
The Milky Way is a galaxy which resides in the Local Group of galaxies. This group is a part of the Local Supercluster and the Local Group is gravitationally bound together. What’s worth noting here is that the Local Supercluster has over 100 galaxy groups and clusters.
Beyond the Local Supercluster lie other superclusters, including the immense Shapley Supercluster. Our cosmic neighborhood extends for hundreds of millions of light-years.
Neighbors in the cosmic neighborhood
The Milky Way interacts with the Local Group. The Andromeda galaxy is our largest neighbor. The two galaxies will collide in billions of years.
Neighbor galaxies orbit the Local Group’s center of mass. Tidal forces shape their forms. Stellar streams trace their orbital dance.
Dwarf galaxies surround the Milky Way. Their orbits provide clues to dark matter. Neighboring galaxies help unveil the local Universe’s structure.
Conclusion
This article has illuminated the immense scale and intricacy of superclusters, the largest structures in our Universe. We have explored how these colossal collections of galaxies emerge from fluctuations in the early Universe.
Superclusters trace an intricate cosmic web shaped by dark matter’s gravity. Our own Local Supercluster and its neighbors reveal our tiny place within this vast cosmic architecture. While thousands of superclusters span the observable Universe, their full number and extent remain unknown; we have attempted to estimate just how many superclusters are there.