34.4 Dark Matter and Closure
3 min read•june 18, 2024
, an invisible form of matter that doesn't interact with light, plays a crucial role in our universe. Scientists have found evidence for its existence through , , and observations.
While neutrinos contribute slightly to , they're too light to account for all of it. The search for dark matter candidates focuses on (massive objects) and (weakly interacting particles), with WIMPs currently favored as the primary component.
Dark Matter
Evidence for dark matter
Top images from around the web for Evidence for dark matter
Guide to Space Archives - Page 111 of 159 - Universe Today View original
Is this image relevant?
The Challenge of Dark Matter | Astronomy View original
Is this image relevant?
Dark Matter and Closure | Physics View original
Is this image relevant?
Guide to Space Archives - Page 111 of 159 - Universe Today View original
Is this image relevant?
The Challenge of Dark Matter | Astronomy View original
Is this image relevant?
1 of 3
Top images from around the web for Evidence for dark matter
Guide to Space Archives - Page 111 of 159 - Universe Today View original
Is this image relevant?
The Challenge of Dark Matter | Astronomy View original
Is this image relevant?
Dark Matter and Closure | Physics View original
Is this image relevant?
Guide to Space Archives - Page 111 of 159 - Universe Today View original
Is this image relevant?
The Challenge of Dark Matter | Astronomy View original
Is this image relevant?
1 of 3
- Galactic rotation curves show observed rotation speeds of galaxies differ from predictions based on visible matter suggesting the presence of additional unseen mass extending beyond the visible galaxy ()
- Gravitational lensing occurs when massive objects like galaxies and galaxy clusters bend light from distant sources with the observed amount of lensing being greater than expected from visible matter alone ()
- in galaxy clusters reveals galaxies moving faster than expected based on the visible mass of the cluster indicating additional unseen mass holding the cluster together ()
- () anisotropies provide information about the total matter content of the universe with observed fluctuations consistent with the presence of dark matter (, )
- Mass-to-light ratios of galaxies and galaxy clusters are much higher than expected from visible matter alone, suggesting the presence of dark matter
Neutrino oscillations and dark matter
- involve neutrinos changing between electron, muon, and tau flavors implying they have non-zero mass (, )
- The discovery of suggests neutrinos have a small but non-zero mass potentially contributing to the total matter content of the universe
- However, neutrinos are likely too low in mass to account for all dark matter and are considered "hot" dark matter moving at relativistic speeds
- The observed large-scale structure of the universe is better explained by "cold" dark matter moving at non-relativistic speeds
Dark matter candidates: MACHOs vs WIMPs
- (MACHOs) are astronomical objects like black holes, neutron stars, or brown dwarfs composed of ordinary but difficult to detect due to low luminosity
- Gravitational surveys have placed constraints on the contribution of MACHOs to dark matter (, )
- (WIMPs) are hypothetical particles interacting only through gravity and the weak nuclear force considered "cold" dark matter candidates moving at non-relativistic speeds
- Examples of WIMPs include predicted by supersymmetric theories and predicted by extra-dimensional theories
- WIMPs are currently favored as the primary component of dark matter due to their "cold" nature and ability to explain the observed large-scale structure of the universe
- MACHOs are constrained by observations to contribute only a small fraction of the total dark matter content compared to WIMPs
- Dark matter can be classified as baryonic (e.g., MACHOs) or non-baryonic (e.g., WIMPs), with being the dominant component
Cosmological implications
- The concept of represents the average density of matter required for a
- , represented by the in Einstein's field equations, is believed to be responsible for the accelerating expansion of the universe
- The combination of dark matter and dark energy influences the overall geometry and fate of the universe, with current observations suggesting a flat universe
Key Terms to Review (43)
Atmospheric Neutrinos: Atmospheric neutrinos are a type of neutrino that are produced in the upper atmosphere when cosmic rays interact with the gases present. These neutrinos are an important tool for understanding the properties of neutrinos and their behavior, particularly in the context of dark matter and the closure of the universe.
Axions: Axions are hypothetical elementary particles proposed as a solution to the strong CP problem in quantum chromodynamics. They are also considered potential candidates for dark matter.
Baryonic Matter: Baryonic matter refers to the ordinary matter that we are familiar with, composed of baryons such as protons and neutrons. It is the type of matter that makes up planets, stars, galaxies, and the visible universe, in contrast to the more elusive dark matter.
Bullet Cluster: The Bullet Cluster is a system of two colliding galaxy clusters that provides some of the best observational evidence for the existence of dark matter. It is a key piece of evidence that supports the current cosmological model of structure formation in the universe.
CMB: CMB, or the Cosmic Microwave Background, is the oldest light in the universe, originating from the time when the universe first became transparent to radiation, around 380,000 years after the Big Bang. It provides a wealth of information about the early universe and its evolution.
Cold Dark Matter: Cold dark matter (CDM) is a hypothetical form of dark matter composed of slowly moving, non-baryonic particles that do not interact with electromagnetic radiation, making it difficult to detect directly. It is a key component of the standard cosmological model and is believed to be the dominant form of matter in the universe, providing the gravitational scaffolding upon which galaxies and larger structures are built.
Coma Cluster: The Coma Cluster is a galaxy cluster located in the northern constellation of Coma Berenices. It is one of the nearest rich clusters of galaxies to the Milky Way, situated at a distance of around 320 million light-years from Earth. The Coma Cluster is a crucial system for understanding the role of dark matter and the overall closure of the universe.
Cosmic microwave background: The cosmic microwave background (CMB) is the thermal radiation left over from the Big Bang, filling the universe almost uniformly. It provides a snapshot of the infant universe approximately 380,000 years after its birth.
Cosmic Microwave Background: The cosmic microwave background (CMB) is the oldest light in the universe, a faint glow that permeates all of space. It is the remnant radiation from the Big Bang, the intense heat and energy that gave birth to the universe nearly 14 billion years ago.
Cosmological constant: The cosmological constant, denoted by $\Lambda$, is a term in Einstein's field equations of general relativity that represents the energy density of empty space, or dark energy. It was originally introduced by Einstein to achieve a static universe but is now associated with the accelerating expansion of the universe.
Cosmological Constant: The cosmological constant is a term in the field of cosmology that represents a constant, uniform energy density inherent in the fabric of space-time. It was originally proposed by Albert Einstein as a way to explain the observed static nature of the universe, but later observations have shown that the universe is actually expanding at an accelerating rate, which is attributed to the cosmological constant.
Critical Density: Critical density is a fundamental concept in cosmology that describes the average density of matter in the universe required for the gravitational attraction to be strong enough to halt the expansion of the universe. It represents the boundary between an open and a closed universe.
Dark Energy: Dark energy is a mysterious and pervasive form of energy that is believed to be the dominant component of the universe, accounting for approximately 68% of its total energy content. It is a fundamental concept in modern cosmology and has profound implications for our understanding of the universe's past, present, and future.
Dark matter: Dark matter is a form of matter that does not emit, absorb, or reflect light, making it invisible and detectable only through its gravitational effects. It constitutes about 27% of the universe's mass-energy content.
Dark Matter: Dark matter is a hypothetical form of matter that cannot be directly observed but is believed to make up a significant portion of the universe's total mass. It is a crucial component in our understanding of cosmology and the structure of the universe.
The term 'dark matter' refers to the fact that this type of matter does not emit, reflect, or absorb light, making it invisible to traditional astronomical observations. Its existence is inferred from its gravitational effects on visible matter and the large-scale structure of the universe.
EROS Survey: The EROS (Extrasolar Radial Velocity Observations Survey) is a long-term project aimed at detecting and characterizing exoplanets, or planets orbiting stars other than our Sun. It utilizes the radial velocity method to measure the tiny wobbles in a star's motion caused by the gravitational pull of orbiting planets, allowing for the indirect detection and study of these distant worlds.
Flat (zero curvature) universe: A flat (zero curvature) universe is a cosmological model in which the geometry of space is Euclidean, meaning it has no overall curvature. This implies that parallel lines never meet, and the angles of a triangle add up to 180 degrees.
Flat Universe: A flat universe is a cosmological model in which the geometry of the universe is flat, meaning that the curvature of space-time is zero. This has important implications for the overall shape and fate of the universe, as well as its evolution and the distribution of matter and energy within it.
Galactic Rotation Curves: Galactic rotation curves are graphs that depict the rotational velocity of stars and other objects orbiting the center of a galaxy as a function of their distance from the galactic center. These curves provide important insights into the distribution of mass within a galaxy and the presence of dark matter.
Gravitational Lensing: Gravitational lensing is the bending of light by the gravitational field of a massive object, such as a galaxy or a cluster of galaxies. This phenomenon is a prediction of Einstein's general theory of relativity and has become an important tool in modern astrophysics and cosmology.
Hot Dark Matter: Hot dark matter refers to a hypothetical component of dark matter in the universe that is composed of high-energy, fast-moving particles, such as neutrinos. These particles have a significant amount of kinetic energy and can travel large distances, influencing the formation and distribution of structures in the universe.
Kaluza-Klein Particles: Kaluza-Klein particles are hypothetical particles that arise from the Kaluza-Klein theory, which proposes the existence of extra spatial dimensions beyond the three dimensions of space and one dimension of time that we observe. These particles are predicted to have masses that are multiples of the inverse size of the extra dimensions.
MACHO Project: The MACHO (Massive Compact Halo Object) project was an astronomical survey conducted to search for dark matter in the form of massive compact halo objects, such as black holes, neutron stars, or brown dwarfs, within the Milky Way galaxy's halo. The project aimed to provide insights into the nature of dark matter, a crucial component in understanding the structure and evolution of the universe.
MACHOs: MACHOs, or Massive Compact Halo Objects, are hypothetical astronomical objects that were proposed as a possible explanation for the observed gravitational effects attributed to dark matter in galaxies and galaxy clusters. These objects are believed to be extremely dense, dark, and massive, making them difficult to detect directly.
Mass-to-Light Ratio: The mass-to-light ratio, also known as the mass-to-luminosity ratio, is a fundamental property that describes the relationship between the mass and luminosity of a celestial object or system. It is a crucial parameter in understanding the composition and structure of galaxies, galaxy clusters, and the overall universe.
Massive compact halo objects: Massive Compact Halo Objects (MACHOs) are a type of dark matter candidate that includes objects like black holes, neutron stars, and brown dwarfs. They are hypothesized to reside in the halos of galaxies and contribute to the overall mass without emitting significant light.
Massive Compact Halo Objects: Massive Compact Halo Objects (MACHOs) are hypothetical astronomical objects that were proposed as a potential explanation for the missing mass, or dark matter, in the universe. These objects are believed to be dense, massive objects that exist in the halos of galaxies, including our own Milky Way.
Microlensing: Microlensing is a gravitational lensing effect where a massive object, such as a star or planet, passes between an observer and a distant light source, temporarily magnifying the light from the source. This phenomenon is used to detect objects that emit little or no light, such as dark matter and exoplanets.
Milky Way: The Milky Way is the galaxy that contains our solar system and is the predominant visible component of the night sky. It is a spiral galaxy composed of hundreds of billions of stars, as well as gas, dust, and other celestial objects.
Negatively curved: Negatively curved space is a type of non-Euclidean geometry where parallel lines diverge and the internal angles of triangles sum to less than 180 degrees. It is often described using hyperbolic geometry.
Neutralinos: Neutralinos are hypothetical particles predicted by supersymmetry theories, often considered as potential candidates for dark matter. They are electrically neutral and interact only via weak nuclear forces and gravity.
Neutralinos: Neutralinos are hypothetical, electrically neutral particles that are predicted to exist in certain theories of particle physics, particularly in supersymmetric extensions of the Standard Model. They are considered to be potential candidates for dark matter, the mysterious and unobserved substance that makes up a significant portion of the universe's total mass.
Neutrino oscillations: Neutrino oscillations are the phenomenon where a neutrino changes its flavor (type) as it propagates through space. This implies that neutrinos have mass and can transform among three types: electron, muon, and tau neutrinos.
Neutrino Oscillations: Neutrino oscillations refer to the phenomenon where neutrinos, which come in three distinct types or 'flavors' (electron, muon, and tau), can spontaneously change from one flavor to another as they travel through space. This quantum mechanical effect is a consequence of neutrinos having a tiny but non-zero mass and the mixing of the neutrino mass eigenstates.
Non-Baryonic Matter: Non-baryonic matter refers to the hypothetical form of matter that does not interact with electromagnetic radiation, making it undetectable by traditional astronomical observations. It is believed to be the dominant component of the universe's total matter content, with baryonic matter (ordinary matter) making up only a small fraction.
Planck Satellite: The Planck satellite was a European Space Agency (ESA) mission that studied the cosmic microwave background (CMB), the oldest light in the universe, to gain insights into the origin and evolution of the cosmos. It provided unprecedented measurements of the CMB, allowing for a better understanding of the composition and structure of the universe.
Positively curved: Positively curved space refers to a type of geometric curvature where the sum of the angles of a triangle is greater than 180 degrees. This occurs in spherical geometries and is often contrasted with flat or negatively curved spaces.
Solar Neutrinos: Solar neutrinos are subatomic particles that are produced in the core of the Sun during nuclear fusion reactions. They are electrically neutral and interact only weakly with matter, allowing them to travel through the Sun and Earth without being absorbed or deflected.
Velocity Dispersion: Velocity dispersion refers to the variation or spread in the velocities of objects within a system, such as stars or galaxies. It is an important concept in the context of dark matter and the closure of the universe, as it provides insights into the dynamics and gravitational interactions within these large-scale structures.
Weakly interacting massive particles: Weakly Interacting Massive Particles (WIMPs) are hypothetical particles that are candidates for dark matter. They interact via the weak nuclear force and gravity, making them hard to detect directly.
Weakly Interacting Massive Particles: Weakly Interacting Massive Particles (WIMPs) are hypothetical subatomic particles that are believed to make up a significant portion of the dark matter in the universe. These particles are characterized by their large mass and their extremely weak interaction with ordinary matter, making them extremely difficult to detect directly.
WIMPs: WIMPs, or Weakly Interacting Massive Particles, are hypothetical subatomic particles that are believed to make up the majority of dark matter in the universe. These particles interact only through the weak nuclear force and gravity, making them extremely difficult to detect directly.
WMAP: WMAP, or the Wilkinson Microwave Anisotropy Probe, was a NASA spacecraft launched in 2001 to measure the cosmic microwave background (CMB) radiation, the oldest light in the universe. The data collected by WMAP has provided crucial insights into the composition, structure, and evolution of the universe, particularly in the context of dark matter and the closure of the universe.