Difference between revisions of "TFNR - Cosmic structures"

Latest revision as of 10:07, 13 May 2025

We have seen that celestial bodies or celestial objects in astronomy are considered as single and compact physical entities that represent the components, the bricks, the building blocks that make up the complex cosmic structures that fill the Universe.

Cosmic structures are therefore more complex physical entities, structured and large arrangements / organizations of interconnected parts, objects and bodies.

Some examples of the structures that populate the cosmos:

• planetary systems
• star clusters, filaments, flows
• nebulae
• galaxies

As planetary systems, star clusters and other intragalactic structures, as nebulae, immersed in the Dark turbulence of the Halo that hosts them, constitute the building blocks of galaxies, as we will see in the next section, galaxies are among the main building blocks of cosmic megastructures, which compose the "universal (dark and visible) cosmic web".

Here I will try to examine the most interesting cosmic structures for understanding the large-scale structure of the Universe: galaxies, medium-sized cosmic structures that can be considered true astronomical structures, bridge the gap between individual stars, stellar groups and cosmic megastructures (groups and clusters of galaxies, superclusters, the cosmic web, etc.). As we will see, galaxies come in various shapes, sizes, and compositions, each playing a crucial role in cosmic evolution.

Let’s examine galaxies in more detail, the strangest, most complex, and vastest structures listed here.

Galaxies

Generally a galaxy is described as a massive system made up of stars, stellar remnants, interstellar gas, dust and dark matter bound together by gravity. The order in which the supposed constituents of galaxies are listed says a lot about the current consolidated knowledge regarding the nature, structure and dynamics of these fascinating celestial objects, the true cosmic building blocks. Lastly, dark matter is almost considered a necessary evil to account for the bizarre dynamics of visible matter. In particular, we talk about the differences between expected and observed values in the curve of the speed of rotation of the material in relation to the distance from the center in disk galaxies.

Although difficult to accept, to understand the nature, structure, origin and dynamics of these celestial objects we must recognize the central role played by Dark Matter and, given the hypotheses we have formulated regarding it, also Dark Energy. These highly structured objects are more than collections, aggregates of gas, dust, rocks, stars, planets, etc. They come in different shapes and sizes, from sprawling spirals like our own Milky Way to densely packed ellipticals and chaotic irregular galaxies. There are billions of galaxies in the Universe, each holding billions—or even trillions—of stars. Galaxies can also be grouped into clusters and superclusters, forming some of the largest structures in the cosmos. Their study helps astronomers understand cosmic evolution, dark matter, and even the fate of the universe itself.

Classification

Depending on their shape, structure and dynamics, we can identify the following types of galaxies:

• Spiral galaxies – Characterized by rotating spiral arms of stars, gas and dust, extending from a central bulge. The Milky Way and Andromeda are a clear example.
• Elliptical galaxies – More spherical or elongated, smooth, round, or oval-shaped, lacking spiral arms, contain older stars with little gas and dust.
• Irregular galaxies – Chaotic, no defined shape, often formed due and influenced by gravitational interactions or mergers / collisions. Contain both young and old stars, sometimes rich in star-forming regions.
• Lenticular galaxies – A hybrid of spiral and elliptical, with a disk structure but no prominent arms. Mostly made up of older stars, with limited gas and dust.

Each type of galaxy has a unique formation history and evolves differently.

Structure

Let's take a look at the structure of a typical galaxy. We must think of a galaxy as a complex system, formed by a rotating bubble (not necessarily a perfect sphere, the real shape determined by internal turbulent dynamics, but above all by external ones, by the interaction with other galactic bubbles, by gravitational and magnetic effects within groups of galaxies and more generally by turbulent dynamics within the cluster of belonging), internally constituted by dark matter and by a boundary of dark energy, and, normally but not necessarily, by ordinary matter of various kinds, all characterized by a variously turbulent dynamics, with ordinary matter and energy entering and exiting (e.m. radiation, particles, gas, dust, stellar bodies, black holes, etc.).

A rotating bubble, not necessarily a perfect sphere, the real shape determined by internal turbulent dynamics, but above all by external ones, by the interaction with other galactic bubbles, by gravitational and magnetic effects within groups of galaxies and more generally by turbulent dynamics within the cluster of belonging. And in this complex turbulent dynamics, in the border regions of the galactic bubble, where the prevailing dark energy of the interacting bubbles overlaps and influences their mutual position and movement, there we will be able to find smaller bubbles that constitute the dark structure of satellite galaxies, of dwarf galaxies that "orbit" the central galaxy, as well as these groups/systems in turn orbit in complex trajectories within larger dark structures to form more extensive galactic groups, clusters, clusters of clusters, and so on. Turbulence within turbulence. Nothing could be further from the poetic (or sacred) image of the perfect celestial spheres, mirror of divine perfection.

A galaxy is not what we see (the visible Ordinary Matter structures, made of materials and objects, surrounded by an invisible Dark Matter / Dark Energy Halo). A galaxy is the invisible Halo of Dark Matter and Dark Energy with some visible matter that tends to gather in the central area of the bubble and which, under certain conditions, tends to accumulate in a rotating disk around a supermassive black hole that is accreting at more or less rapid pace depending on the quantity and dynamics of the available material falling towards the galactic center.

In fact, their visible part, made up of ordinary matter and radiation, represents only a small part of these cosmic objects. The most extensive, massive and relevant part for its overall structure and dynamics is what we call "dark".

Dark Matter and Dark Energy, absolutely related components, two aspects of the same "substance", are therefore not only the main component in terms of quantity, Mass, but are the most important elements for the structure and dynamics of a galaxy. Without DM and DE the existence of a galactic bubble is not possible.

The dark structure is foundational, it is the main, constitutive part of the galaxy. The visible part of the galaxy is formed because there is a bubble, represented by the Dark Alone, capable of triggering and guiding its formation processes. The dark and visible parts coevolve in the construction of the complex structure partly invisible and partly visible that constitutes the galaxy. The Dark Alone is not made up of objects, Particles, familiar materials. It is made up of Dark Matter in the internal part and Dark Energy in the boundary of the bubble towards the outside, towards the extragalactic environment. The quasi-sphere that constitutes the boundary between the internal part of Dark Matter (negative Mass, Perturbation level lower than the average universal level or of the surrounding cosmic region, extended environment) and the surrounding part of Dark Energy (positive Mass, Perturbation level higher than the average universal level or of the surrounding cosmic region) is a surface with zero Mass.

I remind you once again that, when I speak of the level of Perturbation, I am referring to the so-called density of Elementary Events, the temporal distributions of elementary spatial fluctuations in resonance around the Planck scale. Temporal distributions that can be lower, higher or equal to the universal average, or to "local" averages of larger regions that include the region we are observing, in this case, a galactic bubble, precisely. According to the General Equivalence Principle, a level of Perturbation greater or lower than the average (as mentioned, by Perturbation we mean the level of temporal distributions of Elementary Events) is equivalent to a greater or lesser rate of temporal flow (rhythm of clocks), but also to a greater or lesser limit speed of the propagation of Causality, Action, Information in the Elementary Field, and again to a temperature of the Field higher or lower than the average, and finally, an even more central aspect in the representation of a massive structure such as a galaxy, equivalent to positive Mass (Dark Energy) or negative (Mass proper) respectively.

From what has been said, in particular with respect to the comparison of the level of Perturbation of a specific region (e.g. a galactic bubble) with the universal average or of "extended neighborhood", it is evident that the Mass (be it positive or negative) is an exquisitely relative concept. It depends on the reference that we assume for its estimate, but above all it depends on the relationship, the relation in fact, between the observed region and the surrounding one in which the first is immersed.

In cases where, due to a collision between two galactic bubbles, the greater inertia of ordinary matter has determined its exit from the Dark Matter and Dark Energy bubble, we can "observe" on one side an empty or partially empty dark galactic bubble. And next to it, we could observe a galaxy (the visible component) without dark matter (with consequent alteration of the shape and the rotation speed curve on a "cosmic" time scale obviously). Perhaps a merger of two disk/spiral galaxies into a single galaxy (ordinary matter, the visible part) with a "strange" shape, which will tend over time to an elliptical shape and, in the right conditions (the progressive repositioning in a rotating dark bubble) and in a time probably still longer, in a new and larger disc/spiral galaxy.

Due to the turbulent dynamics and interactions of this objects and their environment, as well as their age and the events that affected them, galaxies can have various extensions (dwarf, normal size, extralarge) and shapes: regular (spiro, elliptical), irregular (colliding / merging galaxies), strange shaped galaxies, etc. Oddly shaped galaxies appear to be the majority. As mentioned, among them we find galaxies that show asymmetric disks in the sense of not being circular or not lying on a plane, etc. These asymmetries are very likely to be influenced by the internal dynamics of the galactic bubble, both for the dark and visible components, but above all by the interaction of the bubble with the surrounding environment, with the other bubbles that interact with it and more generally with the entire environment of the cluster and the section of the cosmic web of which it is part.

As mentioned above, it is really difficult to determine the shape of galaxies, galaxies in the complete sense (DM/DE Halo + Visible Matter/Energy). Dark halos have shapes that depend both on internal factors (distribution of mass, total energy and its distribution, turbulence and internal rotation, interactions between the dark and visible components) and on external factors (gravitational, kinetic, chirality and spin of the bubble with the extragalactic/intergalactic environment, interaction with other galactic bubbles, frictional/friction of the boundary Dark Energy components, mass ratios between the bubble and the surrounding ones, turbulent dynamics internal to the galaxy cluster, collisions, decelerations, etc).

Let's try to list the main galactic components (their presence, shape, composition and dynamics depend on the type of galaxy):

• Dark (invisible) components
  • Dark Energy shell - An invisible component that represents the outer shell of the Dark Halo. Complementary part to the inner core composed of Dark matter. It influences the gravitational behavior of the galaxy, but above all its interaction with the extragalactic environment and the possible formation of new Ordinary matter that will be attracted towards the inner regions of the Halo.
  • Dark Matter turbulent Halo – An invisible component that occupies the inner part of the Dark Halo and influences the formation, motion stability and gravitational behavior of the galaxy. It is not "an invisible structure surrounding the galaxy", but a dark structure that occupies the entire inner part of the galaxy, made of a single Vortex type InfoStructure of Dark Matter (widely extended, low density, turbulent, polydynamic), and extends far beyond the internal region that hosts the structures of (visible) Ordinary Matter, the luminous galaxy that we can observe. Detected through gravitational lensing and rotation curve studies.
• Ordinary (visible) components
  • Gas & Dust Components – Clouds of gas and dust where new stars are forming. Unlike spiral galaxies, elliptical galaxies contain little gas and dust, which limits new star formation.
    • Interstellar Medium (ISM) – The gas and dust spread throughout a galaxy, crucial for star formation.
    • Molecular Clouds – Dense regions where new stars form.
    • Ionized Gas Regions – Found in active galaxies, often influenced by black hole activity.
  • Stellar components – Young, hot stars in spiral arms; older, cooler stars in elliptical regions.
    • Central supermassive black hole – A supermassive complex object with its accretion disc, jets, etc.
    • Galactic Bulge – A dense, central region containing older stars and sometimes a supermassive black hole, influencing the dynamics of the galaxy.
    • Galactic Disc – Found in spiral and lenticular galaxies, hosting younger stars, gas, and dust.
    • Stellar Halo – A diffuse, extended region containing old stars, globular clusters, and dark matter. Stars in elliptical galaxies are spread out more uniformly, lacking a clear disk or arms. Most of these stars are older and redder, meaning there is little ongoing star formation.
  • Large-Scale Galactic Structures
    • Spiral Arms – In spiral galaxies, these curved regions contain young, hot stars, glowing nebulae, and star-forming regions. The arms appear brighter because they host active stellar nurseries.
    • Bars – Found in barred spiral galaxies, influencing gas flow and star formation.
    • Rings – Some galaxies have star-forming rings, possibly due to past interactions.
    • Shells & Tidal Streams – Remnants of past mergers, visible in some elliptical galaxies.
• Other components
  • Kinematic & Dynamical Components
    • Rotational Motion – Spiral galaxies rotate, while elliptical galaxies exhibit random stellar motion.
    • Velocity Dispersion – Measures the spread of stellar velocities, crucial for understanding galaxy stability.
    • Density Waves – Spiral arms are maintained by density waves, triggering star formation.
  • Magnetic Fields
    • Galaxies possess large-scale magnetic fields that influence cosmic-ray propagation and interstellar matter dynamics.
    • Typically measured in microgauss (µG), with spiral galaxies exhibiting structured magnetic field patterns along their arms.

Physical quantities that describe structure, properties and dynamics of galaxies

In astronomy, different physical quantities are used to describe the properties and dynamics of galaxies. These are fascinating systems governed by a mix of gravitational, magnetic, and quantum processes. Here are key parameters and how they are measured:

• Structural Parameters (define a galaxy’s structural properties)
  • Extension (Size & Scale)
    • Diameter: Measured in light-years (ly) or kiloparsecs (kpc) (1 kpc = 3,260 ly).
    • Scale Length: The characteristic radius of a galaxy’s disc, useful for comparing galaxy structures.
  • Galaxy Morphology: Classified using the Hubble sequence, e.g., Sa, Sb, Sc (based on the tightness of spiral arms and the size of the central bulge).
  • Structural elements
    • Spiral Arms: The number, shape, and pitch angle of the spiral arms.
    • Bulge-to-Disk Ratio: The relative size of the central bulge compared to the disk.
    • Galactic Disk Thickness: The vertical extent of the disk in relation to its diameter.
• Gravitational and Kinematic Parameters
  • Mass & Matter Composition
    • Total Mass: Measured in solar masses (M☉), where 1 M☉ = the mass of the Sun.
    • Dark Matter Fraction: Determines how much of the galaxy’s mass is invisible and detected only by gravitational effects.
  • Rotation & Velocity
    • Rotational Speed: Measured in kilometers per second (km/s), indicating how fast stars and gas orbit the center.
    • Rotation Curve: A plot showing how rotational velocity varies with distance from the center, crucial for studying dark matter.
  • Radial Velocity & Motion
    • Redshift (z): Determines how fast a galaxy is moving away due to the expansion of the universe.
    • Radial Velocity: The speed at which a galaxy moves toward or away from Earth, measured via Doppler shifts in spectral lines.
• Chirality of Rotation
  • Chirality refers to the handedness of a galaxy’s spiral arms (clockwise vs. counterclockwise rotation).
  • Statistically, galaxies don’t have a universal preferred direction, but their spin is influenced by their formation history and surroundings.
  • Studying galaxy rotation chirality helps understand large-scale cosmic structures and asymmetries.
• Angular Momentum
  • A key quantity describing a galaxy's rotation and mass distribution.
  • Defined by L = r × p (position vector × momentum).
  • Influences galaxy evolution, mergers, and interactions with surrounding matter.
• Velocity Dispersion
  • In elliptical galaxies or galactic bulges, velocity dispersion measures the random motions of stars rather than ordered rotation.
  • Expressed in km/s, higher dispersion indicates older, more stable galaxy structures.
• Photometric Parameters
  • Star Formation & Luminosity
    • Star Formation Rate (SFR): Indicates how many stars form per year, measured in M☉ per year.
    • Luminosity: Measured in solar luminosities (L☉), describing total energy output.
  • Metallicity (Chemical Composition)
    • Metallicity refers to the abundance of elements heavier than hydrogen and helium in a galaxy.
    • Measured as metallicity fraction or [Fe/H] (iron-to-hydrogen ratio) to compare different stellar populations.
    • Younger galaxies or star-forming regions tend to have higher metallicity due to stellar evolution enriching the interstellar medium.
• Surface Brightness & Luminosity Profile
  • Surface brightness describes how light is distributed across a galaxy, measured in magnitudes per square arcsecond.
  • Different galaxy types exhibit unique brightness distributions, with exponential profiles common in spirals and de Vaucouleurs profiles in ellipticals.
• Environmental Parameters
  • Galaxy Environment: The influence of nearby galaxies, clusters, or intergalactic medium.
  • Star Formation Rate: Often linked to gas density and the availability of molecular clouds.
• Magnetic Fields
  • Galaxies possess large-scale magnetic fields that influence cosmic-ray propagation and interstellar matter dynamics.
  • Typically measured in microgauss (µG), with spiral galaxies exhibiting structured magnetic field patterns along their arms.
  • Magnetic fields affect star formation, gas flow, and interactions between galaxies.

Formation

Galaxies form through a fascinating interplay of cosmic forces, primarily driven by gravity and dark matter. Here are some key points about galaxy formation:

Early Universe & Dark Matter: Galaxies begin as small density fluctuations in the early universe. Dark matter plays a crucial role in shaping these structures by providing the gravitational framework for normal matter to accumulate.

Gas Cooling & Star Formation: Over time, gas cools and condenses within dark matter halos, leading to the formation of stars and, eventually, galaxies.

Mergers & Evolution: Galaxies grow by merging with other galaxies, leading to larger and more complex structures. These interactions can trigger bursts of star formation and shape the galaxy’s morphology.

Types of Galaxies: Some galaxies evolve into spirals, like the Milky Way, while others become elliptical or irregular due to environmental factors and interactions.

Supermassive Black Holes & Feedback: Many galaxies host supermassive black holes at their centers, which influence their evolution through powerful jets and radiation.

Interactions

Galactic interactions Mergers and collisions – Galaxies can collide, triggering bursts of star formation and reshaping their structure.

Galaxy interactions occur when two or more galaxies influence each other gravitationally, leading to fascinating cosmic events. Here are some key aspects:

Types of Interactions: Galaxies can experience minor interactions, where a smaller galaxy disturbs the spiral arms of a larger one, or major mergers, where two galaxies collide and eventually merge into a single entity.

Effects on Star Formation: When galaxies interact, their gas clouds can compress, triggering bursts of star formation. Some interactions lead to starburst galaxies, where new stars form at an accelerated rate.

Galaxy Collisions: Unlike traditional collisions, galaxy mergers involve gravitational interactions rather than direct physical impacts. These events can reshape galaxies, forming new structures and even activating supermassive black holes.

Future of the Milky Way: Our own galaxy, the Milky Way, is on a collision course with the Andromeda Galaxy. In billions of years, they will merge, forming a new, larger galaxy.

If you're interested in simulations of galaxy interactions, researchers use advanced computer models to study how galaxies evolve over time.

Gravitational influence – Nearby galaxies exert forces on each other, sometimes forming groups or clusters of galaxies.

Evolution

Cosmic evolution – Over billions of years, galaxies grow, merge, and evolve, shaping the large-scale structure of the universe.

Galactic evolution is the process by which galaxies change over time, influenced by factors like star formation, mergers, and interactions with their environment. Here are some key aspects:

Formation & Early Growth: Galaxies began forming when the universe was only a few hundred million years old. They grew around dense pockets of dark matter, which helped pull in gas and dust to create stars.

Star Formation & Structure: Over billions of years, galaxies evolve as stars form, die, and enrich their surroundings with heavier elements. Spiral galaxies maintain their structure through ongoing star formation, while elliptical galaxies tend to have older stars and less gas.

Mergers & Transformations: Galaxies frequently collide and merge, reshaping their structure. Some spiral galaxies evolve into elliptical ones through these interactions.

Supermassive Black Holes: Most galaxies host supermassive black holes at their centers, which influence their evolution by regulating star formation through powerful jets and radiation.

Observing Evolution: Astronomers study galactic evolution by observing distant galaxies, essentially looking back in time due to the finite speed of light. The Hubble Ultra Deep Field, for example, captures galaxies as they appeared billions of years ago.

In more detail or A closer look

Let's assume a well-formed ideal galaxy:

-> IMAGES

In conclusion

Galaxies are very fascinating structures, with various shapes, articulated structures and complex dynamics, in constant evolution.

In short, let's summarize the most characterizing aspects:

• what we can observe through telescopes is not the entire galaxy, but only the part made of Ordinary (visible) Matter capable of emitting electromagnetic radiation,
• the preponderant part of the Mass / Energy and spatial extension of a galaxy is constituted by its Dark structure (Dark Matter and Energy,
• to simplify a lot, a galaxy, especially a spiral galaxy, can be imagined as a gigantic gravitational well, which in spiraling orbits and multiple evolutionary lines tends to carry the galactic and extragalactic materials that enter the galactic bubble towards the central SMBH, where it is compacted and partly redistributed by radiation pressure, polar jets, powerful magnetic fields and gravitational pushes,
• the formation of galaxies is a slow and complex process, much slower than commonly believed. A process through which, extragalactic materials, which are incessantly formed in the friction areas of the dark cosmic web (giant voids, clusters and superclusters Halos, galactic Halos especially in the crowded nodes of the cosmic web, etc.), enter the galactic bubbles and through gravitational, kinetic, chiral and magnetic processes tend to progressively coagulate into objects and celestial bodies, in their incessant and tortuous descent towards the galactic center.