10.4 Cosmic Web and Voids
2 min read•august 9, 2024
The is a vast network of , sheets, and that shape the universe's large-scale structure. Galaxies and form intricate patterns, connecting clusters and creating empty regions spanning millions of light-years.
Studying these structures helps us understand how gravity and influence cosmic evolution. From massive to empty voids, the cosmic web reveals the universe's complex architecture and the forces shaping it over billions of years.
Large-Scale Structures
Filaments and Sheets in Cosmic Web
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- Filaments form elongated structures connecting and superclusters
- Consist of dark matter and galaxies stretching across millions of light-years
- Sheets represent flat, pancake-like structures of matter in the cosmic web
- Form interconnected network with filaments, creating a honeycomb-like pattern
- Gravity plays crucial role in shaping filaments and sheets over cosmic time
- Computer simulations help visualize (Millennium Simulation)
Nodes and Superclusters
- Nodes represent dense regions where multiple filaments intersect
- Contain massive galaxy clusters and act as gravitational focal points
- Superclusters form largest known structures in the universe
- supercluster encompasses Milky Way and neighboring galaxy clusters
- Spans approximately 520 million light-years in diameter
- Contains about 100,000 galaxies with a total mass of 100 million billion solar masses
- Named "Laniakea" meaning "immense heaven" in Hawaiian
Cosmic Voids
Void Characteristics and Formation
- Vast, nearly empty regions between filaments and sheets in cosmic web
- Typically span 30 to 300 million light-years in diameter
- Form through gravitational collapse of matter into surrounding structures
- Contain significantly fewer galaxies compared to cosmic average
- driven by dark energy, causing accelerated cosmic expansion
- Largest known void called "" spans about 330 million light-years
Void Statistics and Analysis
- provide insights into large-scale structure distribution
- Include measurements of void size distribution, shape, and clustering properties
- quantifies likelihood of finding empty regions
- measures spatial clustering of voids
- describes shape and orientation of voids in cosmic web
- Computational methods () used to identify and analyze voids
Void Galaxies and Cosmic Variance
- exist within underdense regions of cosmic voids
- Tend to be smaller, bluer, and less massive than average galaxies
- Experience less gravitational influence from surrounding structures
- Provide unique environment for studying galaxy evolution in isolation
- refers to statistical fluctuations in galaxy distribution
- Affects observations of large-scale structure on different cosmic scales
- Researchers account for cosmic variance when analyzing cosmological data
- Impacts interpretation of galaxy surveys and measurements of cosmic properties
Key Terms to Review (25)
Boötes Void: The Boötes Void is one of the largest known voids in the universe, located in the direction of the constellation Boötes. It spans approximately 330 million light-years in diameter and contains very few galaxies compared to typical regions of space, making it an intriguing feature of the cosmic web structure. Its existence challenges our understanding of galaxy formation and distribution within the large-scale structure of the universe.
Cosmic microwave background: The cosmic microwave background (CMB) is the afterglow radiation from the Big Bang, permeating the universe and providing a snapshot of the infant cosmos about 380,000 years after the event. This faint glow of microwave radiation is crucial for understanding the early universe's conditions, the formation of cosmic structures, and the overall evolution of the cosmos.
Cosmic variance: Cosmic variance is the statistical uncertainty in measurements of the large-scale structure of the universe due to the limited size of the observable universe. This concept arises because different regions of the universe can have different properties, leading to variations in observed data. Essentially, it reflects the idea that we cannot obtain a complete picture of the universe just by observing a single patch of it; variations can lead to different conclusions about the cosmic web and the cosmic microwave background radiation.
Cosmic web: The cosmic web is the large-scale structure of the universe, characterized by a vast network of filaments composed of dark matter and galaxies that interconnect and surround enormous voids. This structure illustrates how matter is distributed in the universe, revealing the underlying gravitational forces and cosmic evolution over time.
Dark energy: Dark energy is a mysterious form of energy that permeates all of space and is responsible for the observed accelerated expansion of the universe. It makes up about 68% of the total energy content of the universe and plays a crucial role in shaping its large-scale structure and future dynamics.
Dark matter: Dark matter is an unseen form of matter that does not emit, absorb, or reflect light, making it invisible to current observational instruments. It makes up about 27% of the universe's mass-energy content and plays a crucial role in the formation and structure of galaxies and cosmic structures.
Filaments: Filaments are elongated structures in the universe that form a part of the cosmic web, connecting galaxies and clusters of galaxies. These structures are crucial in understanding the large-scale distribution of matter in the universe and play a vital role in galaxy formation and evolution, influencing how matter is accumulated and structured on cosmic scales.
Galaxy clusters: Galaxy clusters are large groups of galaxies held together by gravity, consisting of hundreds to thousands of individual galaxies, along with dark matter and hot gas. These clusters serve as important laboratories for studying galaxy formation and evolution, revealing the effects of feedback mechanisms on their development, the role they play in large-scale structure formation, and how they fit into the cosmic web.
George Efstathiou: George Efstathiou is a prominent astrophysicist known for his contributions to our understanding of the large-scale structure of the universe, particularly in relation to the cosmic web and voids. His work has significantly influenced how scientists view the distribution of galaxies and the role of dark matter in shaping the universe's architecture.
Gravitational Lensing: Gravitational lensing is the bending of light from distant objects due to the gravitational field of a massive object, such as a galaxy or cluster, located between the observer and the light source. This phenomenon allows astronomers to study the distribution of mass in the universe, providing insights into various cosmic structures and the nature of dark matter.
Inflation Theory: Inflation Theory proposes that the universe underwent an extremely rapid expansion, or 'inflation,' shortly after the Big Bang, leading to the uniformity of the cosmic microwave background radiation and the large-scale structure of the universe we observe today. This theory helps explain why the universe appears so homogeneous and isotropic on large scales and addresses some key problems in cosmology, such as the horizon problem and flatness problem.
Lambda Cold Dark Matter Model: The Lambda Cold Dark Matter (ΛCDM) model is a widely accepted cosmological framework that describes the evolution of the universe, combining the effects of dark energy, represented by the cosmological constant (Λ), and cold dark matter. This model explains how the universe expanded from an initial hot, dense state and evolved into the large-scale structure we observe today, including galaxies, clusters, and voids. It provides insights into cosmic phenomena and supports the existence of dark matter through its ability to explain the observed gravitational effects in the cosmos.
Laniakea: Laniakea is a massive supercluster of galaxies that contains the Milky Way and spans over 520 million light-years. It is significant for its role in the structure of the universe, connecting numerous galaxy clusters and providing insight into cosmic evolution and the large-scale distribution of matter.
Large-scale structure formation: Large-scale structure formation refers to the process by which matter in the universe organizes into a complex network of galaxies, clusters, and superclusters, creating a 'cosmic web' that defines the large-scale distribution of galaxies. This structure arises from the gravitational interactions of dark matter and baryonic matter, shaping the universe on scales of hundreds of millions of light-years. Understanding this formation helps explain the overall evolution of the cosmos and provides insights into fundamental cosmological principles.
Redshift Surveys: Redshift surveys are observational studies that measure the redshift of light from distant galaxies, allowing astronomers to determine their distances and map the large-scale structure of the universe. These surveys help reveal the distribution of galaxies, the evolution of cosmic structures over time, and the overall geometry of the universe, contributing to our understanding of its expansion and the cosmic web.
Superclusters: Superclusters are massive groups of galaxies that are bound together by gravity, forming some of the largest known structures in the universe. These enormous cosmic structures consist of numerous clusters and groups of galaxies and can span hundreds of millions of light-years across. Superclusters play a significant role in understanding the large-scale structure and evolution of the universe, as they provide insights into how galaxies and matter are distributed on a grand scale.
Two-point correlation function: The two-point correlation function is a statistical tool used to quantify the spatial distribution of galaxies or other cosmic structures by measuring how the density of these objects varies with distance. It provides insights into the clustering properties of matter in the universe, helping to reveal patterns like the cosmic web and the presence of voids.
Void Ellipticity: Void ellipticity refers to the degree to which cosmic voids, which are large, underdense regions in the universe, deviate from a perfect spherical shape, often exhibiting an elongated or elliptical form. This ellipticity can provide insights into the underlying gravitational dynamics of large-scale structures, such as the cosmic web, and help researchers understand the distribution and evolution of matter in the universe.
Void expansion: Void expansion refers to the phenomenon in cosmology where large, empty regions of space, known as voids, increase in size as the universe continues to expand. This process is a critical aspect of understanding the large-scale structure of the universe, as voids are interconnected with the denser regions of matter, forming a cosmic web. Voids play a significant role in the evolution of the universe and help scientists comprehend how galaxies and galaxy clusters are distributed.
Void Galaxies: Void galaxies are galaxies that exist within cosmic voids, which are large, relatively empty regions in the universe with significantly fewer galaxies than average. These galaxies are typically found at the edges of voids and often have unique characteristics, such as lower luminosity and a different star formation history compared to their counterparts in denser regions. Understanding void galaxies helps in exploring the structure of the universe and the distribution of matter within it.
Void Probability Function: The void probability function is a statistical tool used to describe the likelihood of finding voids, or large empty regions, in the universe as a function of their size. This function helps astronomers understand the distribution and properties of cosmic voids within the larger structure of the universe, highlighting how these voids fit into the overall cosmic web and their role in galaxy formation and evolution.
Void statistics: Void statistics refers to the statistical analysis of the distribution and properties of cosmic voids, which are large, relatively empty regions in the universe. These voids are significant in understanding the large-scale structure of the cosmos, as they provide insight into the distribution of matter and the dynamics of cosmic evolution. Analyzing void statistics helps researchers comprehend the formation and behavior of these voids within the framework of the cosmic web.
Voids: Voids are large, nearly empty regions in the universe that contain very few galaxies and other matter, contrasting with the denser areas filled with galaxy clusters and filaments. These cosmic voids play a crucial role in understanding the large-scale structure of the universe and the distribution of matter, shedding light on cosmic evolution and the formation of high-redshift galaxies.
Watershed Algorithm: The watershed algorithm is a powerful image processing technique used for segmentation that treats an image as a topographic surface, where pixel intensity represents elevation. It identifies and delineates regions in the image, called watersheds, by simulating the flow of water over the surface, allowing for the separation of distinct structures within data. This method is essential in analyzing cosmic structures and voids, as it helps in the identification of different regions in the cosmic web.
Yasushi Suto: Yasushi Suto is a prominent astrophysicist known for his contributions to the understanding of the large-scale structure of the universe, particularly in relation to the cosmic web and voids. His research has provided insights into how galaxies are distributed in space, emphasizing the significance of dark matter and its role in shaping the universe's structure. Suto's work has been influential in improving models that explain the formation and evolution of cosmic structures, connecting theoretical predictions with observational data.