Events
Astronomers have discovered largest spiral galaxy, the larger of which no one has ever seen. Moreover, they claim that currently we are witnessing the birth of another galaxy as a result of the collision of two galaxies.
Incredible spiral galaxy NGC 6872 was noticed by astronomers several decades ago and was considered one of the largest star systems in the Universe, however, only recently it was proven that it is the largest spiral of all known to science.
Features of the largest galaxy NGC 6872
The width of the galaxy NGC 6872 is 522 thousand light years- this is 5 times greater than the width of our galaxy Milky Way. A relatively recent collision with another galaxy likely caused fresh stars began to appear in one of her sleeves, which will ultimately lead to the formation of a new galaxy.
These discoveries were made by an international group of scientists from Brazil, Chile and the USA who examined the images space telescope NASA GALEX. This telescope is capable of recording ultra-violet rays the youngest and hottest stars.
Galaxy NGC 6872 in all its glory
The unusual size and appearance of the galaxy NGC 6872 is due to its interaction with a smaller galaxy IC 4970 , whose mass is only one fiftieth mass of the giant galaxy. This odd couple is located 212 million light years from Earth in southern constellation Pavlina.
Astronomers believe that large galaxies, including our own, are growing due to mergers with other galaxies. These processes last for billions of years, during which some galaxies absorb other, smaller ones.
The yellow circle shows a cluster of young stars that form a fresh galaxy
An interesting fact is that when the galaxies NGC 6872 and IC 4970 interact, not one large one is formed, but one very small galaxy. The northeastern arm of NGC 6872 stands out quite strongly in the image; new stars are unlikely to form here, but at its other end (at the northwestern end) there is a fainter object that looks like a dwarf galaxy, the researchers said.
By analyzing the energy distribution, the team discovered that the two arms of the galaxy NGC 6872 consist of stars of different ages. The youngest stars are located in the region of the northwestern arm, that is, in the region of the proposed new dwarf galaxy. The stars get older closer to the center of NGC 6872.
The most beautiful galaxies in the Universe
Andromeda Galaxy
Distance from Earth: 2.52 million light years
This galaxy is most nearby galaxy to our own, and also one of the most beautiful. It can be seen on a clear night in the area of the Andromeda constellation. Previously it was believed that this galaxy was the largest in the nearby group of galaxies, but later it turned out that the Milky Way is much more massive.
This is what the sky will look like in 3.75 billion years, when the Andromeda Galaxy approaches our Milky Way.
Galaxy Sombrero
Distance from Earth: 28 million light years
This spiral galaxy is located in the region Virgo constellation. She has bright core, incredibly large central part and a brightly highlighted, smooth dust rim like a ring. Galaxy in appearance somewhat reminiscent of a sombrero, that's why it got its name. At the center of this galaxy there is large black hole, which is of great interest to astronomers.
This galaxy is visible even with the help of amateur telescopes
Group of galaxies – Antennae Galaxies
Distance from Earth: 45 million light years
In the constellation of the Raven you can see a curious cluster of galaxies that forms incredible space landscapes. This galaxy is currently passing starburst, that is, stars are formed in it at a relatively high speed.
Spectacular landscape of the Antennae galaxies
Black Eye Galaxy in the constellation Coma Berenices
Distance from Earth: 17 million light years
Galaxy M 64 or as it is often called Black eye, very unusual the way it happens from 2 stuck together galaxies, rotating in different directions. It has an impressive dark rim of dust that stands out against the bright core.
The Black Eye Galaxy is very popular among amateur astronomers
Large Whirlpool Galaxy
Distance from Earth: 23 million light years
Also known as Messier 51, this galaxy was named whirlpool because of its resemblance to a whirlpool. She is in the area constellation Canes Venatici and has a small companion - the galaxy NGC 5195. This galaxy is one of most famous spiral galaxies and is easily visible in amateur telescopes.
The Whirlpool Galaxy and its companion are best observed in the spring and summer
Strange galaxy NGC 3314A in the constellation Hydra
Distance from Earth: 117 and 140 million light years
In fact, these are 2 galaxies: NGC 3314A and B, which did not collide with each other, but simply overlap one another from our vantage point.
Overlapping galaxies
Spiral galaxy M 81 - Bode galaxy in the constellation Ursa Major
Distance from Earth: 11.7 million light years
Named after Johann Bode, the German astronomer who discovered it, this galaxy is one of the most beautiful galaxies known to us. It is located in the area constellations Big Dipper and is quite visible. In addition to M81, the constellation also contains 33 galaxies.
Bode's Galaxy Boasts Nearly Perfect Sleeves
Beautiful ring galaxy Hoag's Object in the constellation Serpens
Distance from Earth: 600 million light years
Named after the scientist who discovered it in 1950, a ring-shaped galaxy has unusual structure and appearance. This galaxy was the first ringed galaxy known science. The approximate diameter of her ring is 100 thousand light years.
On outside rings predominate bright blue stars , and closer to the center there is a ring of more reddish stars, which are probably much older. Between these rings is a darker ring. How exactly was it formed Hoag's object, is unknown to science, although several other similar objects are known.
Hoag's Object photographed by the Hubble Space Telescope in July 2001
Cigar Galaxy in the constellation Ursa Major
Distance from Earth: 12 million light years
Galaxy M 82 or, as it is also called, Cigar is a satellite of another galaxy - M 81. It is notable for the fact that it is located in its center supermassive black hole, around which two more less massive black holes revolve. Also in this galaxy, stars are formed at a relatively high rate. In the center of this galaxy, young stars are born 10 times faster than within our galaxy Milky Way.
The incredibly beautiful Cigar Galaxy
Galaxy NGC 2787 in the constellation Ursa Major
Distance from Earth: 24 million light years
Lenticular galaxy no. NGC 2787 is middle link between elliptical and spiral galaxies and looks very unusual: its sleeves are barely visible, and there is a bright core in the center.
Galaxy NGC 2787. Image taken using the Hubble Space Telescope.
The starry sky has attracted people's gaze since ancient times. The best minds All peoples tried to comprehend our place in the Universe, imagine and justify its structure. Scientific progress 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 materials. Now any schoolchild has an idea of what our Galaxy looks like according to 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 roughly translated from ancient Greek means “milk”. This is how 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 Hercules, illegitimate son Zeus, and in anger splashed breast milk. The drops formed a star trail, visible on clear nights. Centuries later, scientists discovered that the observed luminaries are only a tiny part of the existing ones. celestial bodies. They gave the name Galaxy or the Milky Way system to the space of the Universe in which our planet is located. After confirming the assumption of the existence of other similar formations in space, the first term became universal for them.
A look from the inside
Scientific knowledge about the structure of part of the Universe, including solar system, took little from the ancient Greeks. Understanding of what our Galaxy looks like has evolved from Aristotle's spherical universe to modern theories, in which there is a place for black holes and dark matter.
The fact that Earth is part of the Milky Way system imposes certain limitations on those trying to figure out what shape our Galaxy has. To answer this question unambiguously, a view from the outside is required, 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 their correlation with the parameters of other space systems available for study.
The information collected allows us to say with confidence that our Galaxy has the shape of a disk with a thickening (bulge) in the middle and spiral arms diverging from the center. The latter contain the most bright stars systems. The diameter of the disk is more than 100 thousand light years.
Structure
The galactic center is hidden interstellar dust, making it difficult to study the system. Radio astronomy methods help to cope with the problem. Waves of a certain length easily overcome any obstacles and allow you to obtain the much desired image. Our Galaxy, according to the data obtained, has an inhomogeneous structure.
Conventionally, we can distinguish two elements connected with each other: the halo and the disk itself. The first subsystem has the following characteristics:
- the shape is a sphere;
- its center is considered to be a bulge;
- the highest concentration of stars in the halo is characteristic of its middle part; as you approach the edges, the density decreases greatly;
- The rotation of this zone of the galaxy is quite slow;
- the halo mainly contains old stars with relatively low mass;
- a significant space of the subsystem is filled with dark matter.
The density of stars in the galactic disk greatly exceeds the halo. In the sleeves there are young and even just emerging
Center and core
The “heart” of the Milky Way is located in Without studying it, it is difficult to fully understand what our Galaxy is like. 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, believed to be the birthplace of stars. In what follows, the first version of the term will be used.
It is difficult to penetrate into the center of the Milky Way visible light: he collides with big amount cosmic dust hiding what our Galaxy looks like. Photos and images taken in infrared range, significantly expand astronomers’ knowledge of the nucleus.
Data on the characteristics of radiation in the central part of the Galaxy led scientists to believe that there is a black hole at the core of the nucleus. Its mass is more than 2.5 million times more mass Sun. Around this object, according to researchers, another, but less impressive in its parameters, black hole rotates. Modern knowledge about the peculiarities 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 adjustments to the way our Galaxy looks: it leads to specific changes in orbits that are not typical for cosmic bodies, for example, near the solar system. The study of these trajectories and the relationship between the speed of movement and the distance from the center of the Galaxy formed the basis of the now actively developing theory of dark matter. Its nature is still shrouded in mystery. The presence of dark matter, which presumably makes up the vast majority of all matter in the Universe, is registered only by the effect of gravity on orbits.
If you dispel all cosmic dust, what the core hides from us, an amazing picture will open to our eyes. Despite the concentration of dark matter, this part of the Universe is full of light emitted by a huge number of stars. There are hundreds of times more of them per unit of space here than near the Sun. About ten billion of them form a galactic bar, also called a bar, of an unusual shape.
Space nut
Studying the center of the system in the long-wavelength range allowed us to obtain a detailed infrared image. Our Galaxy, as it turns out, has a structure at its core that resembles a peanut in a shell. This “nut” is the bridge, which includes more than 20 million red giants (bright, but less hot stars).
The spiral arms of the Milky Way radiate from the ends of the bar.
Work related to finding the "peanut" in the center star system, not only shed light on the structure of our Galaxy, but also helped to understand how it developed. Initially, in the space of space there was an ordinary disk, in which a jumper formed over time. Influenced internal processes the bar changed its shape and began to resemble a nut.
Our home on the space map
The activity occurs both in the bar and in the spiral arms that our Galaxy possesses. They were named after the constellations where sections of the branches were discovered: the arms of Perseus, Cygnus, Centaurus, Sagittarius and Orion. Near the latter (at a distance of at least 28 thousand light years from the core) is the Solar System. This area has certain characteristics, according to experts who have made possible occurrence life on Earth.
The galaxy and our solar system rotate along with it. The patterns of movement of individual components do not coincide. stars are sometimes included in the spiral branches, sometimes separated from them. Only luminaries lying on the boundary of the corotation circle do not make such “travels”. These include the Sun, protected from powerful processes constantly occurring in the arms. Even a slight shift would negate all other benefits for the development of organisms on our planet.
The sky is in diamonds
The Sun is just one of many similar bodies that our Galaxy is full of. Stars, single or grouped, total more than 400 billion according to the latest data. The closest one to us, Proxima Centauri, is part of a system of three stars, along with the slightly more distant Alpha Centauri A and Alpha Centauri B. The most bright point the night sky, Sirius A, is located in Its luminosity, according to various sources, exceeds the solar one by 17-23 times. Sirius is also not alone; he is accompanied by a satellite bearing a similar name, but marked B.
Children often begin to get acquainted with what our Galaxy looks like by searching the sky North Star or Alpha Ursa Minor. It owes its popularity to its position above the North Pole of the Earth. The luminosity of Polaris is significantly higher than Sirius (almost two thousand times brighter than the sun), but she cannot challenge Alpha's rights Canis Major for the title of the brightest due to its distance from Earth (estimated from 300 to 465 light years).
Types of luminaries
Stars differ not only in luminosity and distance from the observer. Each is assigned a certain value (the corresponding parameter of the Sun is taken as a unit), the degree of surface heating, and color.
Supergiants have the most impressive sizes. Most high concentration substances per unit volume differ neutron stars. Color characteristic inextricably linked with temperature:
- reds are the coldest;
- heating the surface to 6,000º, like the Sun, gives rise to a yellow tint;
- white and blue luminaries have a temperature of more than 10,000º.
May vary 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 taken by telescopes are amazing.
The data collected on their basis helped to reconstruct the process that led to the outbreak and 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 interacting. Astronomers have found that the Milky Way has repeatedly absorbed its neighbors. Similar processes are expected in the future. Over time, it will include the Magellanic Cloud and a number of other dwarf systems. The most impressive event is expected in 3-5 billion years. This will be a collision with the only neighbor that is visible from Earth with the naked eye. As a result, the Milky Way will become an elliptical galaxy.
The endless expanses of space amaze the imagination. 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 what part of grandiose world we are.
Doctor pedagogical sciences E. LEVITAN.
Scheme for the classification of galaxies, according to Hubble (1925).
Galaxy NGC 4314 (constellation Aquarius).
Irregular galaxies: on the left - the Large Magellanic Cloud, on the right - the Small Magellanic Cloud.
A huge elliptical galaxy in the constellation Virgo is the radio source Virgo A. It is almost a spherical galaxy. In all likelihood, it is very active - the emission of a bright jet of substance is visible.
Galaxy NGC 4650 A (constellation Centaur). The distance to it is 165 million light years.
A gas nebula (M27), which is located in our Galaxy, but very far from us - at a distance of 1200 light years.
In front of you is not a galaxy, but the Tarantula 30 Doradus nebula - a famous landmark of the Large Magellanic Cloud.
“A long time ago, in a galaxy far, far away...” - these words usually begin the films of the famous Star Wars series. Can you imagine how large the number of such “far, far away” galaxies is? For example, about 250 galaxies that we see as a point brighter than 12 m are known. Galaxies whose brightness is even weaker - up to 15 m - are about 50,000. The number of those that can only be photographed by a very powerful, for example 6-meter, telescope at the limit of his capabilities - many billions. With the help of a space telescope, you can see even more of them. All together, these star islands are the Universe - the world of galaxies.
People living on Earth did not immediately understand this. First they had to discover their own planet - Earth. Then - the solar system. Then - our own star island - our Galaxy. We call it the Milky Way.
After some time, astronomers discovered that our Galaxy has neighbors, that the Andromeda Nebula, the Large Magellanic Cloud, the Small Magellanic Cloud and many other nebulous spots are no longer our Galaxy, but other, independent stellar islands.
So man looked beyond the boundaries of his Galaxy. It gradually became clear that the world of galaxies is not only amazingly large, but also diverse. Galaxies vary dramatically in size, appearance and the number of stars included in them, luminosity.
The founder of extragalactic astronomy, which deals with these issues, is rightfully considered to be the American astronomer Edwin Hubble (1889-1953). He proved that many "nebulae" are actually other galaxies consisting of many stars. He studied more than a thousand galaxies and determined the distance to some of them. Among galaxies, he identified three main types: spiral, elliptical and irregular.
Now we know that spiral galaxies occur more often than others. More than half of the galaxies are spiral. These include our Milky Way, the Andromeda galaxy (M31), and the Triangulum galaxy (M33).
Spiral galaxies are very beautiful. In the center is a bright core (a large, close cluster of stars). Spiral branches emerge from the core, twisting around it. They consist of young stars and clouds of neutral gas, mainly hydrogen. All branches - and there may be one, two or several of them - lie in a plane coinciding with the plane of rotation of the galaxy. Therefore, the galaxy has the appearance of a flattened disk.
Astronomers for a long time could not understand why galactic spirals, or, as they are also called, arms, do not collapse for so long. There has been a lot on this issue different hypotheses. Now most galaxy researchers are inclined to believe that galactic spirals are waves of increased density of matter. They are like waves on the surface of water. And those, as is known, do not transfer matter during their movement.
To make waves appear on a calm water surface, it is enough to throw at least a small stone into the water. The appearance of spiral arms is probably also associated with some kind of shock. These could be movements in the very mass of stars inhabiting this galaxy. A connection with the so-called differential rotation and “bursts” during star formation cannot be ruled out.
Astrophysicists quite confidently said that it is in the arms of spiral galaxies that the bulk of newly born stars are concentrated. But then information began to appear that the birth of stars may also occur in the central regions of galaxies (see “Science and Life” No. 10, 1984). It sounded like a sensation. One of these discoveries was made quite recently, when the galaxy NGC 4314 was photographed using the Hubble Space Telescope (photo below).
Galaxies called elliptical, in appearance they differ significantly from spiral ones. In photographs they look like ellipses with to varying degrees compression. Among them are lens-like galaxies and nearly spherical star systems. There are both giants and dwarfs. About a quarter of the brightest galaxies are classified as ellipticals. Many of them are characterized by a reddish color. For a long time, astronomers considered this as one piece of evidence that elliptical galaxies are mainly composed of old (red) stars. Recent observations from the Hubble Space Telescope and the ISO infrared telescope refute this point of view (see “Science and Life” nos. and).
Among the elliptical galaxies there are such interesting objects as the spherical galaxy NGC 5128 (constellation Centaur) or M87 (constellation Virgo). They attract attention as the most powerful sources of radio emission. A special mystery of these and several spiral galaxies is their cores. What is concentrated in them: supermassive star clusters or black holes? According to some astrophysicists, a dormant black hole (or several black holes) may be lurking at the center of our Galaxy, shrouded in clouds of opaque interstellar matter, or, for example, in the Large Magellanic Cloud.
Until recently, the only sources of information about the processes taking place in the central regions of our and other galaxies were observations in the radio and X-ray ranges. For example, extremely interesting data on the structure of the center of our Galaxy was obtained by a team of scientists led by Academician R. Sunyaev with the help of the Russian orbital observatories Astron and Granat. Later, in 1997, using the infrared camera of the American Hubble Space Telescope, astrophysicists obtained images of the core of the elliptical galaxy NGC 5128 (Centaur A radio galaxy). It was possible to detect individual details located at a distance of 10 million light years from us (about 100 light years in size). What emerged was an impressive picture of a riot of hot gas swirling around some center, possibly a black hole. However, it is possible that the monstrous activity of the nuclei of galaxies like this is associated with other violent events. After all, there is a lot of unusual things in the life history of galaxies: they collide and sometimes even “devour” each other.
Finally, let's turn to the third (according to Hubble classification) type of galaxies - wrong(or irregular). They are distinguished by a chaotic, patchy structure and do not have any a certain shape.
This is exactly what happened to the two relatively small galaxies closest to us - the Magellanic Clouds. These are the satellites of the Milky Way. They are visible to the naked eye, although only in the sky of the Earth's Southern Hemisphere.
You probably know that South Pole the world is not marked in the sky by any noticeable star (unlike North Pole world, next to which Ursa Minor is now located - the North Star). The Magellanic Clouds help determine the direction to the South Pole. The Big Cloud, the Little Cloud and the South Pole lie at the vertices of an equilateral triangle.
The two galaxies closest to us received their names in honor of Ferdinand Magellan in the 16th century at the suggestion of Antonio Pigafetta, who was the chronicler of the famous trip around the world. In his notes, he noted everything unusual that happened or was observed during Magellan's voyage. I didn’t ignore these foggy spots in the starry sky.
Although irregular galaxies are the smallest class of galaxies, their study is very important and fruitful. This is especially true for the Magellanic Clouds, which attract Special attention astronomers, first of all, because they are almost next to us. The Large Magellanic Cloud is less than 200 thousand light years away, the Small Magellanic Cloud is even closer - about 170 thousand light years.
Astrophysicists are constantly discovering something very interesting in these extragalactic worlds: unique observations of a supernova exploding in the Large Magellanic Cloud on February 23, 1987. Or, for example, the Tarantula Nebula, in which last years many amazing discoveries have been made.
Several decades ago, one of my teachers, Professor B. A. Vorontsov-Velyaminov (1904-1994), made great efforts to attract the attention of his colleagues to interacting galaxies. In those days, this topic seemed exotic to many astronomers, not representing special interest. But years later, it became clear that the work of Boris Aleksandrovich (and his followers) - studies of interacting galaxies - opened a new, very important page in the history of extragalactic astronomy. And now no one considers exotic not only the most bizarre (and not always understandable) forms of interaction between galaxies, but even “cannibalism” in the world of giant star systems.
"Cannibalism" - the mutual "eating" of galaxies by each other (their merging during close approaches) - is captured in photographs. According to one hypothesis, our Milky Way could become a “cannibal”. The basis for this assumption was the discovery of a dwarf galaxy in the early 90s. There are only a few million stars in it, and it is located at a distance of 50 thousand light years from the Milky Way. This “baby” is not so young: it arose several billion years ago. How will it end long life, it’s hard to say yet. But the possibility cannot be ruled out that it will someday get closer to the Milky Way, and it will absorb it.
Let us emphasize once again that the world of galaxies is incredibly diverse, amazing and largely unpredictable. And astronomy lovers will be able to follow the news of extragalactic astronomy, which is now rapidly developing. So expect new information, new photographs of the most extraordinary galaxies.
More and more often you will encounter different abbreviations and abbreviations indicating types of galaxies, came to the conclusion that it is necessary to write a separate article on this topic in parallel and independently, so that if you have any questions or misunderstandings about the types of galaxies, you simply refer to this short article.
There are very few types of galaxies. There are 4 main ones, with 6 some additions. Let's figure it out.
Types of galaxies
Looking at the diagram above, let's go in order, let's figure out what the letter and the adjacent number (or another additional letter) mean. Everything will fall into place.
1. Elliptical galaxies (E)
Type E galaxy (M 49)
Elliptical galaxies have an oval shape. They lack a central bright core.
The number that is added after English letter E divides this type into 7 subtypes: E0 - E6. (some sources report that there may be 8 subtypes, some 9, it doesn’t matter). It is determined by a simple formula: E = (a - b) / a, where a is the major axis, b is the minor axis of the ellipsoid. Thus, it is not difficult to understand that E0 is ideally round, E6 is oval or flattened.
Elliptical galaxies constitute less than 15% of total number all galaxies. They lack star formation and consist mainly of yellow stars and dwarfs.
When observed through a telescope, they are not of great interest, because It will not be possible to examine the details in detail.
2. Spiral galaxies (S)
S-type galaxy (M 33)
The most popular type of galaxy. More than a half of all existing galaxies - spiral. Our galaxy Milky Way is also spiral.
Because of their “branches” they are the most beautiful and interesting to observe. Most of stars located in close proximity from the center. Further, due to rotation, the stars scatter, forming spiral branches.
Spiral galaxies are divided into 4 (sometimes 5) subtypes (S0, Sa, Sb and Sc). In S0, the spiral branches are not expressed at all and have a light core. They are very similar to elliptical galaxies. They are also often taken out to separate type - lenticular. Such galaxies make up no more than 10% of the total number. Next come Sa (often simply written S), Sb, Sc (sometimes Sd is also added) depending on the degree of twisting of the branches. The older the additional letter, the less degree twists and “branches” of the galaxy surround the core less and less.
The “branches” or “arms” of spiral galaxies have many young ones. Active star formation processes take place here.
3. Spiral galaxies with a bar (SB)
SBb type galaxy (M 66)
Spiral galaxies with bar(or also called “barred”) are a type of spiral galaxy, but contain a so-called “bar” that passes through the center of the galaxy - its core. Spiral branches (sleeves) diverge from the ends of these bridges. In ordinary spiral galaxies, branches radiate from the core itself. Depending on the degree of twisting of the branches, they are designated as SBa, SBb, SBc. The longer the sleeve, the older the additional letter.
4. Irregular galaxies (Irr)
Type Irr Galaxy (NGC 6822)
Irregular galaxies do not have any clearly defined form. They have a “ragged” structure, the core is not distinguishable.
No more than 5% of the total number of galaxies have this type.
However, even irregular galaxies have two subtypes: Im and IO (or Irr I, Irr II). Im have at least some hint of structure, some symmetry or visible boundaries. IO are completely chaotic.
5. Galaxies with polar rings
Polar Ring Galaxy (NGC 660)
This type of galaxy stands apart from others. Their peculiarity is that they have two stellar disks that rotate under different angles each other relative to each other. Many believe that this is possible due to the merger of two galaxies. But precise definition Scientists still have no idea how such galaxies were formed.
Majority polar ring galaxies are lenticular galaxies or S0. Although they are rarely seen, the sight is memorable.
6. Peculiar galaxies
Peculiar Tadpole Galaxy (PGC 57129)
Based on the definition from Wikipedia:
Peculiar galaxy is a galaxy that cannot be classified into a specific class, since it has pronounced individual characteristics. There is no clear definition for this term, and the assignment of galaxies to this type may be disputed.
They are unique in their own way. Finding them in the sky is not easy and requires professional telescopes, but what you see looks amazing.
That's all. I hope nothing complicated. Now you know the basics types (classes) of galaxies. And when getting acquainted with astronomy or reading articles on my blog, you will not have questions about their definition. And if, suddenly, you forget, immediately refer to this article.
The 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. Today this is the most large cluster black holes discovered in galaxies, not counting 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, it is formed spiral shape galaxies.
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 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 in 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 specific shape - round or spiral, hence the name. Gravitational forces other galaxies influence their shape, stretching or twisting it. Merging with other galaxies, as well as their close proximity can change their shape.
Collision of galaxies
Galaxies sometimes wander into outer space, meeting each other. Sometimes they join groups which are called clusters. Some galaxy clusters very large and include 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 is its gravitational field changed shape 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 space in a wide range.
The Andromeda Galaxy captured with a new camera high resolution using a Subaru telescope
The Andromeda Galaxy, located just 2.52 million light years from Earth, also known as M31. She is the closest to us spiral galaxy and is considered 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 the new HSC instrument to compile new detailed statistics everyone famous galaxies , as well as get clearer images of the most distant ones, and then explore how massive objects are able to bend 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 an elephant is 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 star cluster, because she is 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.