From the earliest times, the starry sky attracted the eyes of people. The best minds of all peoples tried to comprehend our place in the Universe, to imagine and justify its structure. Scientific progress has allowed us to move in the study of the vast expanses of space from romantic and religious constructions to logically verified theories based on numerous factual material. Now any schoolchild has an idea of what our Galaxy looks like according to the latest research, who, why and when gave it such a poetic name and what its expected future is.
origin of name
The expression "Milky Way Galaxy" is essentially a tautology. Galactikos in an approximate translation from ancient Greek means "milk". So the inhabitants of the Peloponnese called the cluster of stars in the night sky, attributing its origin to the hot-tempered Hera: the goddess did not want to feed Heracles, illegitimate son of Zeus, and sprinkled breast milk in anger. Drops formed a star path visible on clear nights. Centuries later, scientists discovered that the observed luminaries are only an insignificant part of existing celestial bodies. To the space of the Universe, in which our planet is located, they gave the name Galaxy or the Milky Way system. After confirming the assumption of the existence of other similar formations in space, the first term became universal for them.
Inside look
Scientific knowledge about the structure of the part of the universe, including the solar system, took little from the ancient Greeks. The understanding of what our Galaxy looks like has gone through evolution from Aristotle's spherical universe to modern theories in which there is a place for black holes and dark matter.
The fact that the Earth is an element of the Milky Way system imposes certain restrictions on those who are trying to figure out what shape our Galaxy has. An unambiguous answer to this question requires a view from the side, and at a great distance from the object of observation. Now science is deprived of such an opportunity. A kind of substitute for an outside observer is the collection of data on the structure of the galaxy and its correlation with the parameters of other space systems available for study.
The information gathered allows us to say with confidence that our galaxy has a disk shape with a bulge (bulge) in the middle and spiral arms diverging from the center. The latter contain the brightest stars of the system. The diameter of the disc is more than 100 thousand light years.
Structure
The center of the galaxy is hidden by interstellar dust, which impedes the study of the system. Radio astronomy methods help to cope with the problem. Waves of a certain length easily overcome any obstacles and allow you to get such a coveted image. Our Galaxy, according to the data obtained, has a heterogeneous structure.
Conventionally, two elements connected with each other can be distinguished: the halo and the disk itself. The first subsystem has the following characteristics:
- its center is considered a bulge;
- the highest concentration of stars in the halo is characteristic of its middle part; with approaching the edges, the density decreases greatly;
- the rotation of this zone of the galaxy is rather slow;
- mostly old stars with a relatively small mass are found in the halo;
- significant space of the subsystem is filled with dark matter.
The galactic disk in star density is much higher than the halo. In the arms there are young and even only emerging space objects.
Center and core
The "heart" of the Milky Way is in the constellation Sagittarius. Without studying it, it’s hard to fully understand what our Galaxy is. The name "core" in scientific works either refers only to the central region with a diameter of only a few parsecs, or includes a bulge and a gas ring, considered to be the origin of stars. Next, the first version of the term will be used.
Visible light penetrates with difficulty into the center of the Milky Way: it encounters a lot of cosmic dust, hiding what our Galaxy looks like. Photos and images taken in the infrared range greatly expand the knowledge of astronomers about the nucleus.
Data on the characteristics of radiation in the central part of the Galaxy prompted scientists to think that there is a black hole in the core of the nucleus. Its mass is more than 2.5 million times the mass of the sun. Around this object, according to researchers, another black hole rotates, but less impressive in its parameters. Modern knowledge about the features of the structure of space suggest that such objects are located in the central part of most galaxies.
Light and darkness
The combined influence of black holes on the motion of stars makes its own corrections in the way our Galaxy looks: it leads to specific changes in the orbits that are uncharacteristic of cosmic bodies, for example, near the solar system. The study of these trajectories and the ratio of motion speeds with distance from the center of the galaxy formed the basis of the currently developing theory of dark matter. Her nature is still shrouded in mystery. The presence of dark matter, presumably constituting the vast majority of all matter in the Universe, is detected only by the effect of gravity on orbits.
If you scatter all the cosmic dust that the core hides from us, a striking picture will open up to your eyes. Despite the concentration of dark matter, this part of the universe is full of light emitted by a huge number of stars. There is a hundred times more of them here per unit of space than near the Sun. About ten billion of them form a galactic bar, also called a jumper, of an unusual shape.
Space nut
Studying the center of the system in the long wavelength range made it possible to obtain a detailed infrared image. Our Galaxy, as it turned out, has a structure in its core that resembles inshell peanuts. This "nut" is a jumper, which includes more than 20 million red giants (bright, but less hot stars).
The spiral arms of the Milky Way diverge from the ends of the bar.
The work related to the discovery of “peanuts” in the center of the star system not only shed light on what our Galaxy was in structure, but also helped to understand how it developed. Initially, in space, there was a regular disk in which a jumper formed over time. Under the influence of internal processes, the bar changed its shape and began to look like a nut.
Our house on the space map
Active star formation occurs both in the jumper and in the spiral arms that our Galaxy possesses. The name was given to them by the constellations where the sections of branches were discovered: the arms of Perseus, Swan, Centaurus, Sagittarius and Orion. Near the latter (at a distance of not less than 28 thousand light-years from the core) is the solar system. This area has certain characteristics, according to experts, which made possible the emergence of life on Earth.
The galaxy and our solar system rotate with it. The patterns of motion of the individual components do not coincide. A large number of stars sometimes enters into the composition of spiral branches, then separated from them. Only luminaries lying on the border of the corotation circle do not make such “trips”. The Sun, protected from powerful processes that constantly occur in the arms, also belongs to them. Even a slight shift would negate all the other advantages for the development of organisms on our planet.
Sky in diamonds
The sun is just one of many such bodies with which our galaxy is full. According to recent data, single or grouped stars total more than 400 billion. Proxima Centauri, the closest to us, is part of a three-star system along with slightly more distant Alpha Centauri A and Alpha Centauri B. The brightest point in the night sky, Sirius A, is in constellations Canis Major. According to various sources, its luminosity exceeds solar by 17-23 times. Sirius is also not alone, he is accompanied by a satellite bearing the same name, but with the mark B.
Children often begin to get acquainted with what our Galaxy looks like by searching the sky for the North Star or Alpha Ursa Minor. It owes its popularity to its position over the North Pole of the Earth. In terms of luminosity, Polyarnaya is significantly higher than Sirius (almost two thousand times brighter than the Sun), but it cannot dispute the rights of Alpha the Great Dog to the title of the brightest due to the distance from the Earth (estimated from 300 to 465 light years).
Types of luminaries
Stars differ not only in luminosity and remoteness from the observer. Each is assigned a specific value (the corresponding parameter of the Sun is taken per unit), the degree of surface heating, color.
The most impressive sizes are super giants. The largest concentration of matter per unit volume is distinguished by neutron stars. The color characteristic is inextricably linked with temperature:
- reds are the coldest;
- heating the surface to 6,000º, like the sun, produces a yellow tint;
- white and blue luminaries have a temperature of more than 10,000º.
The luminosity of a star can change and reach a maximum shortly before its collapse. Supernova explosions make a huge contribution to understanding what our Galaxy looks like. Photos of this process, obtained by telescopes, are amazing.
The data collected on their basis helped to restore the process that led to the outbreak, and to predict the fate of a number of cosmic bodies.
The future of the Milky Way
Our Galaxy and other galaxies are constantly in motion and interact. Astronomers have found that the Milky Way repeatedly swallowed neighbors. Similar processes are expected in the future. Over time, it will include the Magellanic Cloud and a number of dwarf systems. The most impressive event is expected in 3-5 billion years. This will be a clash with the Andromeda Nebula, the only neighbor that is visible from Earth to the naked eye. As a result, the Milky Way will become an elliptical galaxy.
The vast expanses of space are amazing. It is difficult for the average person to realize the scale of not only the Milky Way or the entire Universe, but even the Earth. However, thanks to the achievements of science, we can imagine, at least approximately, a part of what a grandiose world we are.