Many facts known today seem so familiar and familiar that it is hard to imagine how they used to live without them. However, the majority of scientific truths did not arise at the dawn of mankind. In many respects, this relates to knowledge of outer space. Types of nebulae, galaxies, stars today are known to almost everyone. Meanwhile, the path to a modern understanding of the structure of the Universe was quite long. People did not immediately realize that the planet is part of the solar system, and it is the galaxies. The types of galaxies began to be studied in astronomy even later, when it came to understand that the Milky Way is not alone and the Universe is not limited to them. The founder of the classification, as well as general knowledge of space outside the "milk road", was Edwin Hubble. Thanks to his research, today we know a lot about galaxies.
Types of galaxies in the universe
Hubble studied nebulae and proved that many of them are formations similar to the Milky Way. Based on the collected material, he described what kind of galaxy has and what types of similar space objects exist. Hubble measured the distances to some of them and proposed his classification. Scientists use it today.
He divided the entire set of systems in the Universe into 3 types: galaxies are elliptical, spiral and irregular. Each type is actively studied by astronomers around the world.
The piece of the Universe where the Earth is located, the Milky Way, refers to the type of "spiral galaxies." The types of galaxies are distinguished on the basis of differences in their shapes that affect certain properties of objects.
Spiral
The types of galaxies distributed throughout the Universe are not the same. According to modern data, spiral-shaped are more common than others. In addition to the Milky Way, the Andromeda Nebula (M31) and the galaxy in the constellation of the Triangle (M33) belong to this type. Similar objects have an easily recognizable structure. If you look from the side of how such a galaxy looks, the top view will resemble concentric circles diverging in water. From a spherical central bulge, called a bulge, spiral arms diverge. The number of such branches varies from 2 to 10. The entire disk with spiral arms is located inside a rarefied cloud of stars, which in astronomy is called the “halo”. The core of the galaxy is a cluster of luminaries.
Subtypes
In astronomy, the letter S is used to designate spiral galaxies. They are divided into types depending on the structural design of the arms and the general shape:
Galaxy Sa: sleeves tightly twisted, smooth and unformed, the bulge is bright and extended;
Sb Galaxy: sleeves are powerful, clear, the bulge is less pronounced;
Galaxy Sc: sleeves are well developed, have a ragged structure, the bulge is poorly visible.
In addition, some spiral systems have a central almost direct jumper (it is called a “bar”). In this case, the letter B (Sba or Sbc) is added to the designation of the galaxy.
Formation
The formation of spiral galaxies, apparently, is similar to the appearance of waves from the impact of a stone on the surface of the water. According to scientists, a certain impetus led to the appearance of sleeves. The spiral branches themselves are waves of increased density of matter. The nature of the shock can be different, one of the options is displacement in the central mass of stars.
Spiral branches are young stars and a neutral gas (the main element is hydrogen). They lie in the plane of rotation of the galaxy, because it resembles a flattened disk. The formation of young stars is also possible at the center of such systems.
Nearest neighbor
The Andromeda nebula is a spiral galaxy: a top view of it reveals several arms emanating from a common center. From the Earth with the naked eye it can be seen as a blurry foggy spot. In size, the neighbor of our galaxy is slightly superior to it: 130 thousand light-years in diameter.
Although the Andromeda nebula is the closest galaxy to the Milky Way, the distance to it is huge. Light needs two million years to overcome it. This fact perfectly explains why flights to a neighboring galaxy are possible only in science fiction books and films.
Elliptical systems
Now consider other types of galaxies. The photo of the elliptical system clearly demonstrates its difference from the spiral counterpart. Such a galaxy has no sleeves. It looks like an ellipse. Such systems can be compressed to varying degrees, represent something like a lens or a ball. In such galaxies, almost no cold gas is encountered. The most impressive representatives of this type are filled with rarefied hot gas, the temperature of which reaches a million degrees and above.
A distinctive feature of many elliptical galaxies is a reddish tint. For a long time, astronomers considered this a sign of the antiquity of such systems. It was believed that they mainly consist of old stars. However, studies of recent decades have shown the fallacy of this assumption.
Education
For a long time there was another hypothesis associated with elliptical galaxies. They were considered the very first to emerge, formed shortly after the Big Bang. Today, this theory is considered obsolete. A great contribution to her refutation was made by German astronomers Alar and Yuri Tumre, as well as the American scientist Francois Schweizer. Their studies and discoveries of recent years confirm the truth of another hypothesis, a hierarchical model of development. According to it, larger structures were formed from rather small ones, that is, galaxies did not form right away. Their appearance was preceded by the formation of star clusters.
Elliptical systems, according to modern ideas, formed from spiral-shaped as a result of the merger of the arms. One of the confirmations of this is the large number of “swirling” galaxies observed in remote parts of space. On the contrary, in the most approximate regions, the concentration of elliptical systems, sufficiently bright and extended, is noticeably higher.
Characters
Elliptical galaxies in astronomy have also received their designations. They use the symbol "E" and numbers from 0 to 6, which indicate the degree of flattening of the system. E0 are galaxies of almost regular spherical shape, and E6 are the most flat.
Surging core
Elliptical galaxies include NGC 5128 systems from the constellation Centaurus and M87, located in Virgo. Their feature is powerful radio emission. Astronomers are primarily interested in the arrangement of the central part of such galaxies. Observations of Russian scientists and studies of the Hubble telescope show a rather high activity of this zone. In 1999, American astronomers obtained data on the core of the elliptical galaxy NGC 5128 (the constellation Centaur). There are in constant motion huge masses of hot gas, swirling around the center, possibly a black hole. There are no exact data on the nature of such processes.
Irregular shape systems
The appearance of the third type of galaxy is not structured. Such systems are ragged objects of chaotic shape. Irregular galaxies are less common in outer space than others, but their study contributes to a more accurate understanding of the processes taking place in the Universe. Up to 50% of the mass of such systems is gas. In astronomy, it is customary to designate similar galaxies by the symbol Ir.
Satellites
Irregularly shaped galaxies include two systems closest to the Milky Way. These are his companions: Big and Small Magellanic Cloud. They are clearly visible in the night sky of the southern hemisphere. The largest of the galaxies is located 200 thousand light-years from us, and the smaller one is separated from the Milky Way - 170,000 sv. years.
Astronomers carefully study the vastness of these systems. And the Magellanic Clouds fully repays for this: very interesting objects are often found in satellite galaxies. For example, on February 23, 1987, a supernova erupted in the Large Magellanic Cloud. Of particular interest is the Tarantula emission nebula.
It is also located in the Large Magellanic Cloud. Here, scientists have discovered an area of constant star formation. Some of the luminaries that make up the nebula are only two million years old. In addition, RMC 136a1, the most impressive star discovered in 2011, is also located here. Its mass is 256 solar.
Interaction
The main types of galaxies describe the features of the shape and arrangement of the elements of these space systems. However, the question of their interaction is no less interesting. It is no secret that all objects of space are in constant motion. Galaxies are no exception. Galactic species, at least some of their representatives could have formed during the merger or collision of two systems.
If we recall what such objects are, it becomes clear how large-scale changes occur during their interaction. A collision releases a tremendous amount of energy. Interestingly, such events are even more likely to occur in outer space than a meeting of two stars.
However, the “communication” of galaxies does not always end in a collision and explosion. A small system can go through its big brother, while disturbing its structure. Thus, formations are formed that are similar in appearance to elongated corridors. They consist of stars and gas and often become zones of formation of new stars. Examples of such systems are well known to scientists. One of them is the Cartwheel galaxy in the constellation Sculptor.
In some cases, the systems do not collide, but pass by each other or only slightly touch. However, regardless of the degree of interaction, it leads to serious changes in the structure of both galaxies.
Future
According to scientists, it is possible that after some rather long time, the Milky Way will swallow up its closest satellite, a relatively recently discovered tiny space-based system located 50 light-years from us. Research data indicates the impressive life expectancy of this satellite, which is likely to end in the process of merging with its larger neighbor.
Collision is a possible future for the Milky Way and the Andromeda Nebula. Now about 2.9 million light-years separates us from our huge neighbor. Two galaxies approach each other at a speed of 300 km / s. A likely collision, according to scientists, will happen in three billion years. However, whether it will happen or the galaxies only slightly hurt each other, today no one knows for sure. For forecasting, there is not enough data on the features of the movement of both objects.
Modern astronomy studies in detail such cosmic structures as galaxies: types of galaxies, features of interaction, their differences and similarities, future. In this area there is still a lot of incomprehensible and requiring additional study. The types of galaxy structures are known, but there is no precise understanding of many details related, for example, to their formation. The current pace of improving knowledge and technology, however, allows us to hope for significant breakthroughs in the future. In any case, galaxies will not cease to be the center of a lot of research. And this is connected not only with the curiosity inherent in all people. Data on cosmic patterns and the life of stellar systems allow us to predict the future of our piece of the universe, the Milky Way galaxy.