When it is observed that there is a set of galaxies in space, we are talking about a hypergalaxyThe number of galaxies that can form one ranges from 100 to 10000. This means that while the Milky Way seems vast to us, there are no words to describe its size. However, there is an example of a hypergalaxy that isn't so vast: the Local Group, in which the Milky Way is located, which consists of about 20 galaxies. To date, around 300 hypergalaxies are known.
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It could also be said that it is a galactic grouping. That is, we would be dealing with a cosmic superstructure It is made up of thousands of galaxies. The baryonic matter of the observable universe is distributed along colossal structures that are called filaments or walls according to their shape, leaving a large number of hollow regions, called voids, with hardly any luminous matter.
Such structures are made up of thousands of aggregates of galaxies with different shapes and sizes. Are colossal macrostructures they are the most recent in the history of the universe. In addition to this, they are held together by dark matter and the force of gravity, but the accelerated expansion of the cosmos could eventually take over and stop the accumulation of matter. Although it is not known if this imposition has already occurred.
On the other hand, it should be noted that the different groups of galaxies that make up the universe are called groups, clusters and superclusters. Each name depends on its size and the number of galaxies it contains. They range from small groups with a dozen galaxies, to large clusters of thousands of galaxies. Superclusters are more complex structures, which are made up of hundreds or thousands of galactic clusters gravitationally interacting with each other.
These are the different types of hypergalaxy
Groups
These are the smallest aggregates of galaxies. The groups have the following properties:
Contain less than 50 galaxies
This implies that this class of hypergalaxies has a diameter of about 2 megaparsec (Mpc).
They also have a mass of the order of 1013 solar masses.
The dispersion of speeds is of the order of 150 km/s.
As mentioned above, the hypergalaxy grouping that contains our galaxy, the Milky Way, is called the Local Group, which consists of more than 20 galaxies. It is also said that there are actually more than 40 galaxies that make up the local group.
Cumulus clouds
The cumulus it is a hypergalaxy or galactic groups that have differentiating characteristics of the groups, since in this case, the galactic accumulation is greater. Abell 2744 is a cluster of galaxies known as the Pandora cluster. As indicated by astronomers, galaxy clusters are larger than groups, as mentioned. However, there is actually no sharp dividing line between the two categories of Hypergalaxy.
If observed visually, clusters appear as collections of galaxies that are self-sustaining by the gravitational pull. However, their velocities are too great for them to remain gravitationally limited by their mutual attractive forces. This observation demonstrates the implication of the presence of an additional invisible component. However, some X-ray observations have revealed the presence of a large amount of intergalactic or intracluster gas.
El intergalactic gas it is very hot, about 108 K. For this reason it is emitted at a high frequency: X-rays. In addition to this, the total mass of the gas is greater than that of all the galaxies in the cluster by a factor of two . However, this gas is still insufficient to maintain the gravitational cohesion of the clusters. The reason for this is that the intracluster gas is in approximate equilibrium with the gravitational field of the entire cluster.
On the other hand, the distribution of the intracluster gas is really fundamental, since this is what allows us to calculate the shape of said field and, for this reason, the total mass of the cluster. It turns out that the total mass deduced is much larger than the mass of the galaxies and hot gas combined. However, the missing component cannot be other than the dark matter whose nature is still unknown.
common cumulus
In a typical cluster, only about 5% of the total mass is in the form of galaxies. On the other hand, it has 10% in the form of hot intracluster gas and the remaining 85% is dark matter. But what predominates most in the clusters are the elliptical and irregular galaxies, this at the rate of the interaction of galaxies.
In addition to this, they are also quite common lenticular galaxies. Of these galaxies it is suspected that in many cases they may come from spiral galaxies that have lost their gas and therefore their ability to form stars. This is due to friction caused by its movement through intergalactic gas or by interactions with other galaxies in the cluster.
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cumulus dynamics
With respect to dynamics of galactic clusters, it can be said that there is a great singularity in this sense. What happens is that they can be considered as a gas of galaxies where the particles that compose it, instead of being atoms or molecules, are rather galaxies. However, this gas has particular conditions since galaxies strongly attract each other while atomic particles do not.
If a gas is normal it can tend to expand and occupy the maximum space, while on the other hand galactic clusters not only tend to expand, but also tend to collapse under its own gravity. This behavior means that they are in a delicate balance between their velocity dispersion and their mass. The more mass the cluster has, the higher the escape velocity.
In the same way, more mass implies greater gravitational forces, which leads to greater accelerations and higher speeds. This implies that in the most massive clusters, the galaxies that compose them move much faster with respect to each other than in the less massive ones.
In the field of gravity is where confines the galaxies in a given volume of space. This is how the walls of an airtight container confine the air inside.
Evolution
The way in which the clusters have been evolving could possibly take two directions. In a case, tend to concentrate more matter adding small groups and other individual galaxies, which leads them to become more and more compact and acquire a spheroidal shape. Meanwhile, said cluster engulfs galaxies and groups, the nucleus of the cluster cannibalizes galaxies from it, turning its center into one or more giant elliptical galaxies.
Such a concentration is what keeps the others orbiting around them and that they will eventually merge into a single giant elliptical galaxy, forming what is known as a fossil galaxy cluster: which is a cluster of galaxies with a single elliptical galaxy at its center. and a lack of bright galaxies in the central regions.
The other course of the evolution of the clusters is less gravitationally bound and can evolve differently. Statistically there is always some galaxy capable of reaching escape velocity to get out of the cluster. These clusters begin to lose galaxies and as they lose mass, the escape velocity decreases, this is what accelerates the loss of more galaxies, causing their fragmentation until total dilution.
This turns out to be a process that can be motivated by the presence of larger cumulus in the vicinity, which will end up devouring the little one.
Properties
The clusters have approximate content ranging from 50 to 1000 galaxies, hot X-ray emitting gas and lots of dark matter. The way these three components are distributed is roughly the same in every cluster. They are estimated to have a total mass ranging from 1014 to 1015 times the solar mass. And in size they normally have a diameter of 8 Mpc.
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superclusters
This hypergalaxy is larger, but not the largest. Groups, clusters, and some isolated galaxies can form larger structures together: this is what they are called superclusters. These groupings would behave in a similar way to cumulus clouds. The difference is that in the supercluster the elementary particles that constitute it would no longer be individual galaxies, but entire galactic groups and clusters that move confined in their colossal gravitational field. An example of a supercluster is the Phoenix cluster.
large-scale structures
They turn out to be the groupings that make up a Hypergalaxy that are the largest in the observable Universe. On the largest scales of visible universe, matter is grouped in filaments and extensive walls or walls surrounded by voids as huge hollow bubbles with superclusters as nodes. The structure appears to resemble that of a sponge.
