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Science
If you look at the night sky with a telescope and can see what the normal eye cannot, you will see a huge number of "stars", many of which are actually star clusters – galaxies. Some of them are clusters of billions and even trillions of stars!
Galaxies are made up of stars, dust and dark matter- all these components are held together using gravitational forces. Some galaxies are capable of colliding and merging.
Black holes of the galaxy
Galaxies come in all shapes and sizes, as well as different ages. Many of them boast black holes in the center. In some cases, these black holes are in the central part of galaxies can be incredibly large and show unprecedented activity.
The region around black holes releases a huge amount of energy that astronomers can observe even over long distances.
Some other galaxies may contain objects such as quasars– the nuclei of galaxies that contain most energy in the Universe.
New black holes
Not long ago, astronomers discovered 26 new black holes in a neighboring galaxy Andromeda. To date, this is the largest cluster of black holes discovered in galaxies other than Milky Way.
Black holes on their own do not emit light, but they can be noticed due to the radiation of the material that falls into them. Before this in the galaxy Andromeda were found 9 black holes, and now 26 more have been added to them.
Formation of galaxies
Astronomers still cannot say exactly how galaxies were formed. After big bang space consisted almost entirely from hydrogen and helium.
Some astronomers believe that with the help of gravitational forces, dust and gas began to be attracted. After that individual stars began to form. These stars began to approach each other, star clusters appeared, and then galaxies.
Other scientists believe that dust and gas first formed galaxies, within which later the stars appeared.
Star Islands
At the beginning of the 20th century, many astronomers believed that the entire Universe lay within our galaxy Milky Way. Others disputed this fact and believed that clusters in the form of spirals consisting of gas and dust, were separate objects. American astronomer Harlow Shapley called them "star islands" or "island universes".
In 1924, another American - Edwin Hubble- discovered several special pulsating stars – Cepheid- in some so-called nebulae and realized that they were located outside the Milky Way.
American astronomer Edwin Hubble (1889-1953)
Thus, it turned out that some objects that were previously considered part of our galaxy actually lie much further from it within other star clusters.
After Hubble measured the distance to individual stars, it went further and began to change how much light galaxies emit due to their movement. He determined that the galaxies around milky way moving away from him at great speeds.
Types of galaxies
Galaxies have been classified based on their shapes. Each type has its own characteristics and different evolutionary development.
Some galaxies, for example Milky Way, have spiral arms that radiate from its center. These galaxies are known as spiral galaxies . They are the most common.
Spiral Milky Way galaxy with a bar in the center
Gas and dust in a spiral galaxy rotate around its center at high speed - several hundred kilometers per second. Thus, a spiral shape of the galaxy is formed.
Some spiral galaxies have jumper – a special structure in the center consisting of gas and dust, which accumulate in the center. Today, gas and dust can be found in any spiral galaxy, these components are responsible for the formation of new stars.
U elliptical galaxies sleeves are missing. They can have the shape of an elongated ellipse or an ideal sphere. This type of galaxy has less dust than spiral galaxies, so the process of forming new stars in them is complete.
Most stars of elliptical galaxies have old age. Although astronomers observe a small number of elliptical galaxies, they believe that there are more than half of them in the Universe.
The remaining 3 percent of galaxies are known as irregular galaxies . They do not have any particular shape - round or spiral, hence the name. Gravitational forces other galaxies influence their shape, stretching or twisting it. Merger with other galaxies, as well as their close proximity can change their shape.
Collision of galaxies
Galaxies sometimes wander through outer space, meeting each other. Sometimes they join groups which are called clusters. Some galaxy clusters are very large and contain thousands of galaxies. There are also small clusters.
Galaxy Milky Way are part of a cluster called Local group, which contains 50 galaxies.
Sometimes galaxies can collide with each other, causing merger. This is very important stage evolution and growth of many galaxies.
Individual stars do not usually collide in a galactic merger, but a new influx of gas and dust leads to increasing the rate of new star formation. The Milky Way will collide with the Andromeda Galaxy in 5 billion years.
The fate of the Andromeda and Milky Way galaxies
Penguin with egg
Amazing image of two colliding galaxies captured by NASA space telescope "Hubble". Two galaxies resemble penguin bending over an egg. Both of these galaxies are located in the region of the Hydra constellation at a distance of 326 million light years from Earth.
Penguin is a spiral galaxy NGC 2936 in which new stars are forming. In many ways she once resembled Milky Way and was shaped like a flat spiral disk. But the orbits of the stars in this galaxy have changed thanks to the approach of another egg-shaped galaxy NGC 2937, which changed its shape with its gravitational field NGC 2936.
Penguin with an egg: an example of a collision between two galaxies (NGC 2936 and NGC 2937)
Andromeda Galaxy (new photo)
In a new amazing photograph of the galaxy closest to the Milky Way Andromeda you can see our neighbor in a completely new light thanks to the latest instrument of the Japanese telescope Subaru. New photos were recently presented at the Hawaii summit.
The new tool, called Hyper-Suprime Cam (HSC), allows you to do clear images of space in a wide range.
Andromeda Galaxy captured new camera high resolution using the Subaru telescope
The Andromeda Galaxy, located just 2.52 million light years from Earth, also known as M31. It is our closest spiral galaxy and is considered to be very similar to the Milky Way.
It can be seen in the night sky even with the naked eye in the form of a dim speck. This object was first described in 964 AD Persian astronomer As-Sufi.
Astronomers plan to use new tool HSC for compilation new detailed statistics of all known galaxies, as well as get clearer images of the most distant ones, and then explore how massive objects capable of bending light using their gravitational field.
Andromeda Galaxy with its moons: M32 (center left) and M110 (bottom)
This data will help scientists map dark matter distribution, discover small galaxies that have just appeared in the Universe. By analyzing the galaxies that play a role gravitational lenses, astronomers will be able to find out how much material there is in the Universe, and also better understand what constitutes an invisible element - dark matter.
Smallest galaxy
An incredibly dim cluster of 1,000 stars that orbits the Milky Way - lightest galaxy by mass ever opened. This dwarf galaxy was discovered in the constellation Aries in 2007 and received the name Segue 2. Its material is held together by a small accumulation of dark matter.
Discover a galaxy smaller than Segue 2- it's the same as open the elephant by size smaller than a mouse , as scientists reported. This galaxy is only 900 times brighter than the Sun, when compared (for comparison) Milky Way 20 billion times brighter than our star.
Galaxy Segue 2 is not a star cluster, since it contains dark matter, which, according to astronomers, acts as “galactic glue.” Recently it became clear that Segue 2 10 times less dense than previously thought.
It is possible that next to Milky Way rotate and other small galaxies, which astronomers cannot yet detect.
In the section Natural sciences to the question Who and when discovered the world of galaxies? given by the author (EXTRIM) the best answer is In 1924, the American scientist E. Hubble, using photographs taken with a telescope with a mirror diameter of 2.5 m, established that the M31 and M3 nebulae are giant galaxy systems consisting of stars and located at an enormous distance from us.
Reply from 2 answers[guru]
Hello! Here is a selection of topics with answers to your question: Who discovered the world of galaxies and when?
Reply from Nikum[guru]
The question of whether nebulae were separate galaxies remained controversial until the early 1920s, when Edwin Hubble's new telescope answered the question. He was able to discern the outer parts of some spiral nebulae as clusters of individual stars and identify Cepheid variables among them. This allowed him to estimate the distance to these nebulae: they were too far away to be part of the Milky Way. In 1936, Hubble created a classification of galaxies that is still used today, called the Hubble sequence.
Reply from Krab Bark[guru]
The assumptions appeared in the mid-18th century with Immanuel Kant. They decided that this was not so, and the galaxies were just nebulae in the Milky Way. It was not until 1924 that it was Edwin Hubble who proved that galaxies are galaxies.
History of the discovery of the galaxy
Most celestial bodies are combined into various rotating systems. Thus, the Moon revolves around the Earth, the satellites of the giant planets form their own systems, rich in bodies. For more high level, The Earth and other planets revolve around the Sun. A natural question arose: is the Sun also part of an even larger system?
The first systematic study of this issue was carried out in the 18th century by the English astronomer William Herschel. He counted the number of stars in different areas of the sky and discovered that there was a large circle in the sky (later it was called the galactic equator), which divides the sky into two equal parts and on which the number of stars is greatest. In addition, the closer the part of the sky is to this circle, the more stars there are. Finally it was discovered that it was on this circle that the Milky Way was located. Thanks to this, Herschel guessed that all the stars we observed form a giant star system, which is flattened towards the galactic equator.
At first it was assumed that all objects in the Universe are parts of our Galaxy, although Kant also suggested that some nebulae could be galaxies similar to the Milky Way. As early as 1920, the question of the existence of extragalactic objects caused debate (for example, the famous Great Debate between Harlow Shapley and Geber Curtis; the former defended the uniqueness of our Galaxy). Kant's hypothesis was finally proven only in the 1920s, when Edwin Hubble was able to measure the distance to some spiral nebulae and show that, due to their distance, they cannot be part of the Galaxy.
Conclusion
The Milky Way Galaxy is one of hundreds of millions of similar star systems discovered in the Universe using large telescopes. It is often called “our star system.” It belongs to large galaxies with rapid rotation and clear spiral arms, in which young hot stars and clouds of gas heated by their radiation, called “emission nebulae,” are concentrated. Using optical telescopes, it is not possible to study the entire Galaxy, since light does not penetrate through dense interstellar clouds of gas and dust, which are especially numerous towards the center of the Galaxy. However for infrared radiation and radio emissions, dust is not a hindrance: with the help of appropriate telescopes, it is possible to explore the entire Galaxy and even break through to its dense core. Observations have shown that the stars and gas in the galactic disk are moving at a speed of about 250 km/s around the center of the Galaxy. Our Sun, together with the planets, also moves at the same speed, making one revolution around the galactic center in about 200 million years.
Literature
1. Yu. N. Efremov - Milky Way
2. Physical encyclopedia / ed. A.M. Prokhorova, Art. "Galactic Center"
3. Kardashev N.S. Phenomenological model of the galactic core // in the book. Results of science and technology. Astronomy series, vol. 24. - M. - 1983.
4. Agekyan T.A. Stars, galaxies, metagalaxy.
Astronomical discoveries
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Astronomy as a science
Galaxies have become the subject of cosmogonic research since the 20s of our century, when their actual nature was reliably established and it turned out that they were not nebulae, i.e. not clouds of gas and dust located near us...
Astronomical map
Galaxies have become the subject of cosmogonic investigations since the 20s of our century, once their active nature was reliably established and it was revealed that they are not nebulae, so do not bother with gas and saw, which are located not far from us...
Structure of the Universe
A galaxy is a collection of stars in a lens-shaped volume. Most of the stars are concentrated in the plane of symmetry of this volume (the galactic plane), a smaller part is concentrated in the spherical volume (the galactic core)...
Exoplanets: history of discovery and modern achievements
Astrometric search. The first attempts to detect exoplanets involved observations of the positions of nearby stars. In 1916, American astronomer Edward Barnard (1857-1923) discovered...
Category: Tags:Edwin Hubble at the 100-inch (2.5-meter) telescope, which was used to measure the distances to galaxies, the redshift and the rate of expansion of the Universe (Palomar Observatory, futura-sciences.com).
Geber Curtis and Harlow Shapley, participants in the "Great Controversy over the Nature of Spiral Nebulae."
Spiral galaxy, side view: disk (stellar and dusty), central bulge (bulge) and halo, which extends far beyond the visible part of the galaxy and consists of tenuous hot gas, stars and dark matter.
Galaxy NGC 891, discovered by Herschel in 1784, is believed to be very similar to our Galaxy (Adam Block / Mount Lemmon SkyCenter / University of Arizona).
Classification of galaxies proposed in 1936 by Edwin Hubble. Images of galaxies were taken by the Spitzer and Hubble orbital telescopes (SIGNS, as amended).
A beautiful group of interacting galaxies (Arp 273) in the constellation Andromeda is located 300 million light years from our Galaxy. Hubble Space Telescope image (NASA, ESA, and the Hubble Heritage Team, STScI/AURA)
So, at the beginning of the 20th century, partly thanks to the discovery of interstellar absorption, people began to correctly understand the parameters of our Galaxy and our place in it. All that remained was to discover the world of galaxies.
It's quite funny that just 100 years ago people weren't sure about the existence of galaxies. If you use a time machine to go back 100 years and, in order not to get bored, take with you a player and a complete set of Star Wars, then the beginning of the film will be incomprehensible to people of that time. They will ask what it is - “ galaxies far, far away"? In 1920, a public debate was held at the National Museum of Natural History in Washington between Geber Curtis and Harlow Shapley on the nature of spiral nebulae. Since the creation of the first large telescopes, people have realized that many nebulae visible in the sky have a special spiral structure. And quite quickly people began to suspect that these were structures similar to our Galaxy. But it was extremely difficult to prove this, since it was not even possible to discern individual stars in these nebulae. Curtis believed that spiral nebulae are giant star systems, stellar islands outside our Galaxy. And Shapley, despite the fact that he was a very good astrophysicist, defended, as we now know, the wrong point of view that all these nebulae are located inside our Galaxy, which is the entire Universe. Of course, truth is not born in such disputes; this dispute has remained in history as an interesting intellectual show. And the answer, of course, came thanks to observations.
A key contribution to understanding the structure of the cosmos was made by Edwin Hubble, who began working with the new 2.5-meter telescope in the early 1920s. At that time it was the most powerful telescope in the world. Now such telescopes are much more accessible; individual universities can relatively easily obtain telescopes of this diameter. Using this telescope, Hubble discovered special variable stars, Cepheids, in several nearby galaxies, most notably the Andromeda Nebula. Look at the photo from real work Hubble (fortunately, now all, at least the classical articles, are available on the Internet). Different symbols denote Cepheids - variable stars that have remarkable property– they pulsate, and these are really physical pulsations. Such a star becomes brighter when it contracts (because it heats up). And the pulsation period is well related to the luminosity of the star. That is, if you observe a pulsation period and see the visible brightness of a star, you can measure its distance. This was discovered at the beginning of the 20th century by Henrietta Leavitt. This is very cool, since it is impossible to measure the distance to stars in the Andromeda Nebula using parallax. Hubble observed a large number of Cepheids (it is very important that it was a large number, not just one or two Cepheids, this had been done before Hubble), reliably conducting a large-scale study, and was able to determine the distance to several nearby galaxies.
At this moment, the amazing world of galaxies truly opened up to humanity. All that remained was to take the last important step and discover the most grandiose phenomenon occurring in nature - the expansion of the Universe.
The release material was kindly provided by Sergei Borisovich Popov - astrophysicist, Doctor of Physical and Mathematical Sciences, Professor Russian Academy Sciences, leading researcher at the State Astronomical Institute named after. Sternberg of Moscow state university, winner of several prestigious awards in the field of science and education. We hope that getting acquainted with the issue will be useful for schoolchildren, parents, and teachers - especially now that astronomy is again included in the list of compulsory school subjects (order No. 506 of the Ministry of Education and Science of June 7, 2017).
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