This is our Galaxy - the Milky Way. She is approximately 12 billion years old. The galaxy is a huge disk with giant spiral arms and a bulge in the center. There are countless such galaxies in space. - First of all, the Galaxy is a large cluster of stars. On average, it contains a hundred billion stars. This is a real stellar incubator - a place where stars are born and where they die. Stars in a galaxy appear in clouds of dust and gas, so-called nebulae.
Before us are the “Pillars of Creation” in the Eagle Nebula - a stellar incubator in the very heart of the Milky Way. Our Galaxy contains billions of stars, many of which are surrounded by planets or moons. For a long time, we knew very little about galaxies. A hundred years ago, humanity believed that the Milky Way was the only galaxy. Scientists called it “our island in the Universe.” Other galaxies did not exist for them. But in 1924, astronomer Edwin Hubble changed the general idea. Hubble observed space using the most advanced telescope of its time, with a lens diameter of 254 centimeters, located at Mount Wilson Observatory near Los Angeles. Deep in the night sky, he saw vague clouds of light that were very far from us. The scientist came to the conclusion that these are not individual stars, but entire star cities, galaxies far beyond the Milky Way. - Astronomers experienced a real space-time shock. In just a year, we have moved from the Universe inside the Milky Way to the Universe of billions of such galaxies. Hubble made one of the greatest discoveries in astronomy. There is not just one galaxy in space, but a great many galaxies. Our Galaxy has a vortex structure, has two spiral arms, and contains about 160 million stars. Galaxy M 87 is a giant ellipse. It is one of the oldest galaxies in the Universe, and the stars within it emit a golden light.
And this is the Sombrero Galaxy, in its center there is a huge luminous core, surrounded by a ring of gas and dust. Professor Michio (Michio) Kaku, physicist:- Galaxies are magnificent. In a sense, they represent the basic unit of the Universe. They are like giant lantern wheels that spin in space. These are real fireworks created by nature itself. Galaxies are huge - real giants. On Earth, distance is measured in kilometers; in space, astronomers use the unit of length “light year” - the distance traveled by light in a year. It is approximately equal to nine and a half trillion kilometers. Professor Lawrence Krauss, astrophysicist:- We are located 25 thousand light years from the center of our Galaxy, and its diameter is 100 thousand light years. But even with such impressive dimensions, it is only a small speck in the vast expanses of space. The Milky Way Galaxy seems huge to us. But compared to other galaxies in the Universe, it is quite small. Our closest galactic neighbor, the Andromeda Nebula, reaches a diameter of 200 thousand light years, 2 times the size of our Milky Way. M 87 is the largest elliptical galaxy in nearby space. It is much larger than Andromeda, but compared to the other giant M 87 it seems tiny. IC 10 11 is 6 million light years wide. This is the largest known galaxy. It is 60 times larger than the Milky Way. So we know that galaxies are huge, they are everywhere. But where did they come from? - One of the most important questions in astrophysics is the origin of galaxies. We still don't have an exact answer to this. The universe began with the Big Bang, which occurred approximately 13.7 billion years ago and was an incredibly hot, very dense phase. We know that nothing like galaxies could have existed at that time. Therefore, we can say that they appeared at the dawn of the Universe. To create stars, you need gravity. To unite stars into galaxies, even more is needed. The first stars appeared just 200 million years after the Big Bang. Then gravity pulled them together. This is how the first galaxies appeared. Professor Lawrence Krauss, astrophysicist:- The Hubble Space Telescope allowed us to look into the past, to get almost to the beginning of time, to the period when the first galaxies were just beginning to form. The Hubble Telescope sees many galaxies, but the light from most of them left its source thousands, millions, even billions of years ago. All this time he was flying towards us. Thus, today we are surveying galaxies that have already become history. Professor Lawrence Krauss, astrophysicist:- If you look deeper into space with the help of Hubble, you can see small specks that hardly resemble existing galaxies. These vague spots of light, clusters of millions, billions of stars that were just beginning to unite. These faint spots are the earliest of the galaxies. They formed about a billion years after the beginning of the Universe. Beyond this time, Hubble is powerless. If we need to explore deeper layers of the past, we need a different telescope. More than the one that can be launched into space. Now we have one in the high desert of Northern Chile. Its name is AST - Atacama Space Telescope. This highest of ground-based telescopes is located at 5190 meters above sea level. - I really like working at AST in extreme weather conditions. It can be very cold here and the winds blow fiercely. But a huge advantage for our work is that the sky is almost always clear. Clear skies are essential for the precise reflectors of AST, which focuses on early galaxies. Professor Suzanne Stags, physicist:- Using AST, we can zoom in on parts of the sky with incredible accuracy. We can also monitor the development of structures such as galaxies and galaxy clusters with extreme image clarity. ANT does not detect visible light, only cosmic microwaves left over from a time when the Universe was several hundred thousand years old. With this telescope you can not only see different galaxies, but also monitor their growth. Professor Suzanne Stags, physicist:- We are able to trace the processes of formation of galaxies and their clusters. We see traces of each of them, from several hundred thousand years from the beginning of the world to the present day. ANT has helped astronomers understand how galaxies have evolved almost since the beginning of time. Professor Michael Strauss, astrophysicist:- We began to answer questions: what galaxies looked like at the beginning of creation, whether they were similar to modern galaxies, how they grew and developed. Astronomers are observing how galaxies have traveled from small clusters of stars to today's network of star systems. Professor Lawrence Krauss, astrophysicist:- According to our current understanding, stars form clusters that unite into galaxies, which, in turn, form clusters of galaxies, and these form superclusters of galaxies - the largest units of space today. Early galaxies were shapeless clumps of stars, gas and dust. Today, the galaxies have taken on a neat, orderly appearance. How did chaotic clusters of stars turn into slender elliptical spiral systems? With the help of gravity. The force of gravity unites the stars and controls their future development. At the center of most galaxies there is an incredibly powerful destructive source of gravity. And our Milky Way is no exception. Galaxies have existed for more than 12 billion years. We know that these vast empires of stars take on a variety of forms, from vortex spirals to enormous balls of stars. Still, much in galaxies remains a mystery to us. Professor Michael Strauss, astrophysicist:- How did galaxies acquire their existing shape? Has a spiral galaxy always been shaped like a spiral? The answer is almost always no. Young galaxies are shapeless, chaotic collections of stars, gas and dust. Only after billions of years do they turn into such organized structures as, for example, a vortex galaxy or our Milky Way. Professor Lawrence Krauss, astrophysicist:- The Milky Way did not grow from one grain, from many. What is now called the Milky Way galaxy was once made up of many formations, shapeless structures that united into a single whole. Small structures converge due to the force of gravity. She gradually pulls the stars together. They spin faster and faster until they take the shape of a flat disk. The stars and gas then form giant spiral arms. This process has been repeated billions of times throughout space. Each galaxy is unique, but they all have one thing in common: they all revolve around their center. For years, scientists have wondered: what is powerful enough to change the behavior of the galaxy? And finally the answer was found. Black hole. And not just any black hole, but a supermassive black hole. - The first clue to the existence of supermassive black holes were galaxies, from the center of which a powerful column of energy burst out. It seemed to us that these black holes were feeding on nearby objects. Sort of like a giant Thanksgiving feast. Supermassive black holes feed on gas and stars. Sometimes the black hole eats them too greedily, and the food is thrown back into space as a beam of pure energy. This is called a quasar. When scientists see a quasar shooting out from the center of a galaxy, they know it has a supermassive black hole. What about our Galaxy? After all, she doesn’t have a quasar. Does this mean that it does not have a supermassive black hole? Andrea Ghez and her team have been trying to figure this out for 15 years. Professor Andrea Ghez, astronomer:- You can find out whether there is a supermassive black hole in the Milky Way by the movement of stars. Stars rotate, obeying the force of gravity, just like the planets around the Sun. However, stars located closer to the center of the Galaxy are hidden by clouds of dust. So Ghez used the giant Keck Telescope in Hawaii to see through the dust. A strange and cruel picture appeared before her eyes. Professor Andrea Ghez, astronomer:- In the center of our Galaxy, everything is taken to the extreme. Objects move at great speed, stars rush past one after another. Everything is bubbling, everything is seething. You will not see this anywhere in our Galaxy. Ghez and her team began taking pictures of some of the stars orbiting closer to the center of the Galaxy. Professor Andrea Ghez, astronomer:- We set ourselves the task of making a video with stars in the center of the Galaxy. I had to be patient and take picture after picture before the stars moved. Photographs of rotating stars have revealed something amazing. Their rotation speed was several million kilometers per hour. Professor Andrea Ghez, astronomer:- The most exciting moment in this experiment was when we received the second image and it became clear that the stars were rotating much faster than usual. This fully confirmed the hypothesis of a supermassive black hole.
The hypothesis was correct. Ghez and her team tracked the stars' trajectory and calculated their location from their center of rotation. There is only one thing powerful enough to spin huge stars around itself: a supermassive black hole. Professor Andrea Ghez, astronomer:- Only the gravitational force of a supermassive black hole causes stars to rotate. Their trajectories became evidence of a supermassive black hole at the center of our Galaxy. The black hole at the center of the Milky Way is gigantic. Its width is 24 million kilometers. Is there a danger to our planet? Professor Andrea Ghez, astronomer:- There is not the slightest danger that we will be sucked into a supermassive black hole. It's too far from us.
Planet Earth is located 25 thousand light years from the black hole at the center of the Milky Way. This is many billions of kilometers, so the Earth is safe. Bye. Supermassive black holes can be a source of powerful gravity. But they do not have enough strength to maintain the connection between the bodies of the galaxy. According to all the laws of physics, galaxies must decay. Why isn't this happening? There is a force in space greater than a supermassive black hole. It cannot be seen and is almost impossible to calculate. But it exists, it's called dark matter, and it's everywhere. Astronomers have discovered that at the center of galaxies there are supermassive black holes that attract stars at high speeds. But black holes are not strong enough to connect all the stars of a giant galaxy into a single whole. What kind of power is this? It remained a mystery until one independent scientist suggested that we were dealing with something unknown. In the 30s of the 20th century, Swiss astronomer Fritz Zwicky wondered why galaxies do not decay. According to his calculations, they do not generate enough gravitational force, therefore, they must scatter throughout space. “He stated: “I see with my own eyes that they do not fall apart, but stick together in a dense group. This means that something is preventing them from falling apart. But their own force of attraction is not powerful enough for this. Therefore, I conclude that there is something that is unknown to mankind, something unimaginable.” He gave it a name - dark matter. It was like a divine revelation. Professor Michio (Michio) Kaku, physicist:- Fritz Zwicky was several decades ahead of his time, and, of course, ran into misunderstandings among his fellow astronomers. But ultimately, he was right. If what Zwicky called dark matter united galaxies into groups, perhaps it also prevented individual galaxies from falling apart. To test this, scientists constructed virtual galaxies on a computer with virtual stars and virtual gravity. - We made a model of the galaxy, populated it with stars in orbits in the shape of a flat disk. Exactly like our Galaxy. And they decided that they had created the ideal galaxy. We wondered whether it would become a spiral or something else. But all our galaxies were falling apart. This galaxy did not have enough gravity to remain a single entity, so Ostriker added it along with virtual dark matter. Professor Jeremy Ostriker, astrophysicist:- Naturally, we wanted to try it, it solved the problem. Everything worked out. The gravitational force of dark matter turned out to be the binding force of the galaxy. Professor Jeremy Ostriker, astrophysicist:- Dark matter plays the role of the galaxy's scaffolding. With its help, galaxies are fixed in place and do not break up into separate bodies. Scientists now suggest that dark matter not only supports the galaxy, but gives impetus to its birth. Professor Michio (Michio) Kaku, physicist:- We believe that the first clusters of dark matter appeared as a result of the Big Bang. After some time, these clusters became obvious - grains from which galaxies grew. But scientists still don’t know what dark matter is. Professor Lawrence Krauss, astrophysicist:- Dark matter remains something inexplicable. We don't understand its essence. But it is definitely made of a different material... Professor Michio (Michio) Kaku, physicist:- ... than you and I. You cannot lean on it, you cannot touch it. Perhaps it is all around us, like a ghost that passes right through you, as if you do not exist at all. We may not know about dark matter, but the cosmos is filled with it. Dr Andrew Benson, astrophysicist:- The weight of dark matter is equivalent to at least six times the weight of the Universe from ordinary matter, that is, from which we are all made, without which it is impossible to imagine the normal operation of the laws of the Universe. However, these laws work. It turns out that dark matter really exists. And recently traces of it were discovered in deep space. Observations of its influence on the behavior of light helped make this statement. The beam path is bent. This phenomenon is called gravitational lensing.
Dr. Andrew Benson, astrophysicist: - The gravitational lens allows us to determine the presence of dark matter. How does it work? Imagine that a beam of light from some distant galaxy is flying towards us. If large accumulations of dark matter are encountered along its path, its trajectory will go around the dark matter under the influence of gravity. If you look at the depths of space through the Hubble telescope, the shape of some galaxies appears distorted and elongated.
This happens because dark matter distorts the image. She kind of puts it in a round aquarium. Dr Andrew Benson, astrophysicist:- By analyzing the outlines of these galaxies and the degree of distortion, it is possible to calculate with a certain accuracy the amount of dark matter in them. It has now become clear that dark matter is an integral part of the cosmos. It has existed since the beginning of time and influences everything, everywhere. It creates conditions for the birth of galaxies and prevents them from decaying. It is not visible to the naked eye, it is not calculated by instruments, but, nevertheless, dark matter is the mistress of the Universe. The galaxies seem to exist separately. There are indeed trillions of kilometers between them, but, nevertheless, the galaxies are united in groups, clusters of galaxies. Clusters of galaxies form superclusters, which include tens of thousands of galaxies. Where does our Milky Way rank among them? Professor Michio (Michio) Kaku, physicist:- A general plan of space shows that our Galaxy is part of a small group of about thirty galaxies. Our Milky Way and the Andromeda Nebula are the largest in it. But on a larger scale, we are just a small part of a supercluster of galaxies called Virgo. Currently, scientists are compiling a general map of the Universe and determining the locations of galaxy clusters and superclusters. This is the Apache Point Observatory in New Mexico, which is home to the Sloan Digital Sky Survey. It's just a small telescope, but it has a unique mission. Sloan's Digital Survey produces the first three-dimensional star map. It will allow us to determine the exact location of tens of millions of galaxies. To do this, the Sloan survey hunts for galaxies far beyond the Milky Way. It precisely determines the location of the galaxy, this information is recorded on aluminum disks. - These aluminum discs are about 30 inches wide and have 640 through holes, each of which is designed for the desired object in space. Space objects are galaxies. Light from the galaxy passes through the hole and further along the fiber optic cable. In this way, information about the distance and location of thousands of galaxies can be recorded and plotted on a three-dimensional map. Dan Long, engineer at Sloan Digital Sky Survey:- We determine their outlines, composition, and also how evenly they are scattered throughout outer space. All this is very important for astronomy, for understanding the laws of the Universe.
Here we see the fruits of their work: the largest three-dimensional map in existence today. The map shows things previously unseen: entire clusters and superclusters of galaxies. And the picture of the world continues to expand. We see that superclusters of galaxies form chains - filaments. The Sloan survey found one 1.4 billion light years across. It was called the Great Wall of Sloan. This is the largest single structure discovered in the history of science.
Dan Long, engineer at the Sloan Digital Sky Survey: “You feel the enormity of this space. Clusters, filaments, and each of these tiny lumps of light are huge galaxies. Not stars, but entire galaxies, and there are hundreds and thousands of them around. The Sloan Survey shows galactic geography on a large scale. Scientists went further. They built an entire Universe in a super-powerful computer. And here you cannot see individual galaxies; it is difficult to even make out their clusters. On the screen you can only see superclusters of galaxies that make up a giant cosmic web of filaments.
Professor Lawrence Krauss, astrophysicist: - If you look closely at the large-scale picture of space, you can discern a pattern of filaments, a cosmic web consisting of galaxies and their clusters that extend in thousands of different directions. From this point, space resembles in its structure a giant sponge. Each filament houses millions of galaxy clusters, all of them connected by dark matter. This computer model shows dark matter shining through tangles of filaments. Dr Andrew Benson, astrophysicist:- Dark matter affects the location of the galaxy in the Universe. Look at galaxies: they are not scattered randomly throughout space. They gather in small groups, which once again indicates the scale of the distribution of dark matter. Dark matter supports the entire macrostructure of space. It links galaxies into clusters, which in turn form superclusters. Superclusters are woven into chains of filaments. Without dark matter, the entire structure of the cosmos will simply fall apart. Here is our Universe close up.
Somewhere in the depths of this gigantic cosmic web, our Galaxy, the Milky Way, nestles in one of the filaments. It has existed for about 12 billion years, and it is about to die in a powerful cosmic collision. Galaxies are vast kingdoms of stars. Some are huge balls, others are complex spirals, but they are all constantly changing. Professor Lawrence Krauss, astrophysicist:- When we look at our Galaxy, it seems to us that it is unchanged and has existed forever. But that's not true. Our Galaxy is in constant motion, its nature has changed over cosmic time. Galaxies not only change, but also move. It happens that galaxies collide with each other, and then one absorbs the other. - In the Universe there is a whole flock of different galaxies that interact and collide with each other - with other members of the flock.
This is NGC 2207. At first glance, it looks like a huge double spiral galaxy, but in fact it is two galaxies colliding. The collision will last for millions of years, and eventually the two galaxies will merge into one. Similar collisions occur everywhere in space, and our Galaxy is no exception. Professor Lawrence Krauss, astrophysicist:- The Milky Way is essentially a cannibal. It acquired its present form by absorbing many smaller galaxies. Even today, small stripes of stars of the former individual galaxies that remained without boundaries, which replenished the Milky Way, are visible on its body. But these are “little flowers” compared to what awaits us in the future. We are rapidly moving towards the Andromeda galaxy, and this does not bode well for the Milky Way. Professor Michio (Michio) Kaku, physicist:- The Milky Way is approaching Andromeda at a speed of approximately 250 thousand miles per hour, which means that in 5-6 billion years our Galaxy will no longer exist. Dr TJ Cox, astrophysicist:- Andromeda is approaching us with all its monstrous mass. When galaxies interact, each of them individually disintegrates, and their bodies gradually mix and grow like a snowball. Professor Michio (Michio) Kaku, physicist:- Two galaxies begin the dance of death.
This is a reproduction of a future collision, accelerated millions of times. When two galaxies collide, clouds of gas and dust fly off in all directions. The gravitational force of merging galaxies tears stars from their orbits and throws them into the dark depths of the Universe. Professor Michio (Michio) Kaku, physicist:- The Judgment Day of the Milky Way will be a picturesque picture, and we will watch the destruction of our Galaxy from the front rows. Gradually, the two galaxies will pass right through each other, and then return to merge into a single whole. Oddly enough, the stars will not collide with each other. They are still too far apart. Dr TJ Cox, astrophysicist:- The stars will just mix. The probability of two separate stars colliding is virtually zero. However, the dust and gas between the stars will begin to heat up. At some point they will ignite, and the colliding galaxies will become white hot. Professor Michio (Michio) Kaku, physicist:- At some point, a real fire may break out in the skies. Dr TJ Cox, astrophysicist:- The Milky Way and Andromeda galaxies will cease to exist. A new galaxy will appear - Melkomeda, which will become a new cosmic unit. The new Melkomed galaxy will look like a huge ellipse without arms or spirals. We will not be able to escape the future. The question is what it will bring to planet Earth. Professor Michio (Michio) Kaku, physicist:- We can either be thrown into outer space along with fragments of the arms of the Milky Way, or sucked into the body of a new galaxy. Stars and planets will be scattered throughout the galaxy and beyond, and for planet Earth this could be a sad end. The Universe will see a collision of galaxies more than once. But the era of galactic cannibalism will also end someday. Galaxies are home to stars, solar systems, planets and moons. The galaxy provides itself with everything it needs. Professor Lawrence Krauss, astrophysicist:- Galaxies are the living blood in the body of the Universe. We exist because we originated within the Galaxy, and everything we see, everything that matters to us, happens within the Galaxy. With all this, galaxies are fragile structures held together by dark matter. Scientists have discovered another active force in the Universe. It is called dark energy. Dark energy acts in opposition to dark matter. If one connects galaxies, then the other separates them from each other. Professor Lawrence Krauss, astrophysicist:- Dark energy, which we have known about for literally one decade, is the dominant feature of the cosmos and represents an even greater mystery. We don't have the slightest idea why it is needed. Dr Andrew Benson, astrophysicist:- It's hard to say what it consists of. We know that it exists, but what it is and what its function remains a mystery. Professor Jeremy Ostriker, astrophysicist:- Dark energy is a strange thing. It seems that outer space is riddled with tiny sources that cause objects to repel each other. Scientists believe that in the distant, distant future, dark energy will win the cosmic battle with dark matter, and galaxies will begin to disintegrate. Professor Lawrence Krauss, astrophysicist:- Dark energy will destroy galaxies. This will happen when other galaxies begin to gradually move away from ours until they disappear from view. And since the galaxies will fly apart at speeds greater than the speed of light, they will literally disappear from our eyes. Not today, not tomorrow, but perhaps in trillions of years we will remain in an empty Universe. Galaxies will become lonely islands in the vast expanses of space. But this will not happen very soon. Today the Universe is thriving, and galaxies create all the conditions for the existence of life. Professor Michio (Michio) Kaku, physicist:- Without galaxies, I wouldn’t be here, you wouldn’t be here, and life might not have arisen at all. We are incredibly lucky: life originated on Earth only due to the fact that our tiny Solar system is located in the right part of the Galaxy. If we had positioned ourselves a little closer to the center, we would not have survived. Professor Michio (Michio) Kaku, physicist:- Life in the center of the Galaxy is very cruel, and if our solar system was located closer to the center, there would be so much radiation that we would not be able to survive. Living too far from the center is also no better. The number of stars at the edges of the Galaxy decreases sharply. We might not exist at all. Professor Michio (Michio) Kaku, physicist:- We can say that we have chosen the golden mean of the Galaxy: not far, not close, but right in the bull’s eye. Scientists believe that this golden belt of the Galaxy may contain millions of stars, and among them there are likely to be other solar systems capable of supporting life. And they are in our own Galaxy. And if we have a habitable zone, it can also exist in other galaxies. Professor Andrea Ghez, astronomer:- The Universe is huge, it presents us with surprises again and again. Professor Jeremy Ostriker, astrophysicist:- Every time we think we have found the answer to a question, it turns out that it has led us to an even bigger question. This sparks interest. Our native Milky Way Galaxy and other galaxies in the Universe pose before us endless questions that require answers, and secrets that have not yet been discovered by anyone. Professor Michio (Michio) Kaku, physicist:- Who would have imagined 10 years ago that we would be able to find a black hole in the center of the Galaxy? Which astronomer would have believed in dark matter and dark energy just 10 years ago? More and more scientists are devoting their research to galaxies. It is in them that the key to understanding the laws of the Universe lies. Professor Lawrence Krauss, astrophysicist:“Isn’t it amazing to live at this point in the history of space on this small planet on the outskirts of a random galaxy and receive answers to questions about the Universe from its very beginning to its very end?” We should endlessly rejoice at this brief moment in the rays of the Sun. Galaxies are born, develop, collide and die. Galaxies are superstars for the world of science. Every astronomer has his favorites. Professor Michael Strauss, astrophysicist:- Vortex galaxy or M51. Professor Jeremy Ostriker, astrophysicist:- If I could hang it on the wall, I would choose the Sombrero Galaxy. Professor Lawrence Krauss, astrophysicist:- The Sombrero Galaxy, ring galaxies - they are very beautiful. Professor Michio (Michio) Kaku, physicist:- My favorite galaxy is the Milky Way. This is my home. We are lucky that the Milky Way provides us with everything we need to live. Our fate directly depends on our Galaxy and on all other galaxies. They created us, they gave shape to our lives, and our future is in their hands.
Bound by the forces of gravitational interaction. The number of stars and sizes of galaxies may vary. Typically, galaxies contain from several million to several trillion (1,000,000,000,000) stars. In addition to ordinary stars and the interstellar medium, galaxies also contain various nebulae. The sizes of galaxies range from several thousand to several hundred thousand light years. And the distance between galaxies reaches millions of light years.
About 90% of the mass of galaxies comes from dark matter and energy. The nature of these invisible components has not yet been studied. There is evidence that many galaxies have supermassive galaxies at their centers. The space between galaxies contains virtually no matter and has an average density of less than one atom per cubic meter. Presumably, there are about 100 billion galaxies in the visible part of the universe.
According to the classification proposed by astronomer Edwin Hubble in 1925, there are several types of galaxies:
- elliptical(E),
- lenticular(S0),
- regular spiral(S),
- crossed spiral(SB),
- incorrect (Ir).
Elliptical galaxies - a class of galaxies with a clearly defined spherical structure and decreasing brightness towards the edges. They rotate relatively slowly; noticeable rotation is observed only in galaxies with significant compression. In such galaxies there is no dust matter, which in those galaxies in which it is present is visible as dark stripes against a continuous background of the stars of the galaxy. Therefore, externally, elliptical galaxies differ from each other mainly in one feature - greater or lesser compression.
The share of elliptical galaxies in the total number of galaxies in the observable part of the universe is about 25%.
Spiral The galaxies are so named because they have bright arms of stellar origin within the disk that extend almost logarithmically from the bulge (the nearly spherical bulge at the center of the galaxy). Spiral galaxies have a central cluster and several spiral arms, or arms, that are bluish in color because they contain many young giant stars. These stars excite the glow of diffuse gas nebulae scattered along with dust clouds along the spiral arms. The disk of a spiral galaxy is usually surrounded by a large spheroidal halo (a ring of light around an object; an optical phenomenon) consisting of old second-generation stars. All spiral galaxies rotate at significant speeds, so stars, dust and gases are concentrated in a narrow disk. The abundance of gas and dust clouds and the presence of bright blue giants indicate active star formation processes occurring in the spiral arms of these galaxies.
Many spiral galaxies have a bar at the center, from the ends of which spiral arms extend. Our Galaxy is also a barred spiral galaxy.
Lenticular galaxies are an intermediate type between spiral and elliptical. They have a bulge, halo and disk, but no spiral arms. There are approximately 20% of them among all star systems. In these galaxies, the bright main body, the lens, is surrounded by a faint halo. Sometimes the lens has a ring around it.
Incorrect galaxies are galaxies that exhibit neither spiral nor elliptical structure. Most often, such galaxies have a chaotic shape without a pronounced core and spiral branches. As a percentage, they make up one quarter of all galaxies. Most irregular galaxies in the past were spiral or elliptical, but were deformed by gravitational forces.
Evolution of galaxies
The formation of galaxies is considered a natural stage of evolution, occurring under the influence of gravitational forces. As scientists suggest, about 14 billion years ago there was a big explosion, after which the Universe was the same everywhere. Then particles of dust and gas began to group, unite, collide, and thus clumps appeared, which later turned into galaxies. The variety of galaxy shapes is associated with the variety of initial conditions for the formation of galaxies. The accumulation of hydrogen gas within such clumps became the first stars.
From the moment of its birth, the galaxy begins to shrink. The contraction of the galaxy lasts about 3 billion years. During this time, the gas cloud transforms into a star system. Stars are formed by the gravitational compression of clouds of gas. When the center of the compressed cloud reaches densities and temperatures sufficient for thermonuclear reactions to occur effectively, a star is born. In the depths of massive stars, thermonuclear fusion of chemical elements heavier than helium occurs. These elements enter the primary hydrogen-helium environment during stellar explosions or during the quiet outflow of matter with stars. Elements heavier than iron are formed during enormous supernova explosions. Thus, first generation stars enrich the primary gas with chemical elements heavier than helium. These stars are the oldest and consist of hydrogen, helium and very small amounts of heavy elements. IN second generation stars the admixture of heavy elements is more noticeable, since they are formed from the primary gas already enriched with heavy elements.
The process of star birth occurs with the ongoing compression of the galaxy, so the formation of stars occurs closer and closer to the center of the system, and the closer to the center, the more heavy elements there should be in the stars. This conclusion agrees well with data on the abundance of chemical elements in stars in the halo of our Galaxy and elliptical galaxies. In a rotating galaxy, the stars of the future halo form at an earlier stage of contraction, when the rotation has not yet affected the overall shape of the galaxy. Evidence of this era in our Galaxy are globular star clusters.
When the compression of the protogalaxy stops, the kinetic energy of the resulting disk stars is equal to the energy of the collective gravitational interaction. At this time, conditions are created for the formation of a spiral structure, and the birth of stars occurs in the spiral branches, in which the gas is quite dense. This third generation stars. Ours is one of them.
The reserves of interstellar gas are gradually depleted, and the birth of stars becomes less intense. In a few billion years, when all gas reserves are exhausted, the spiral galaxy will turn into a lenticular galaxy, consisting of faint red stars. Elliptical galaxies are already at this stage: all the gas in them was consumed 10-15 billion years ago.
The age of galaxies is approximately the age of the Universe. One of the secrets of astronomy remains the question of what the nuclei of galaxies are. A very important discovery was that some galactic nuclei are active. This discovery was unexpected. Previously, it was believed that the galactic core was nothing more than a cluster of hundreds of millions of stars. It turned out that both the optical and radio emission of some galactic nuclei can change over several months. This means that within a short time, a huge amount of energy is released from the nuclei, hundreds of times greater than that released during a supernova explosion. Such nuclei are called “active”, and the processes occurring in them are called “activity”.
In 1963, objects of a new type were discovered located beyond the boundaries of our galaxy. These objects have a star-shaped appearance. Over time, they found out that their luminosity is many tens of times greater than the luminosity of galaxies! The most amazing thing is that their brightness changes. The power of their radiation is thousands of times greater than the power of active nuclei. These objects were named . It is now believed that the nuclei of some galaxies are quasars.
» Galaxies and the Universe
When observing, how can a comet without a tail be distinguished from an ordinary nebula?
The comet moves relative to the stars. This movement can be noticed in a few hours or even in a few tens of minutes.
What stars are there most in galaxies?
There are significantly more stars with low masses than stars with large masses. The bulk of low-mass stars are red dwarfs.
Why do old stars in spiral galaxies form a spherical subsystem, while young stars form a thin rotating disk?
The oldest stars in such galaxies occupy a region of space approximately the same as that occupied by the protogalactic cloud from which they formed. Centrifugal forces prevented the remaining gas from compressing in the galactic plane, throwing it away from the center. As a result, a thin rotating gas disk appeared in the plane of rotation of spiral galaxies, in which the youngest stellar objects in the galaxy are formed.
What is the oldest cosmic body that fell into human hands?
The age of one of the samples of lunar rock brought to Earth by the Apollo 15 expedition is estimated at 4 billion 150 million years.
Which galaxies are visible to the naked eye?
One such galaxy is our Milky Way galaxy. We view it from the inside, so it appears as a bright stripe in the night sky. The next galaxy is the famous Andromeda nebula. It is visible to the naked eye in the form of a luminous speck. In addition to these galaxies, the satellites of our galaxy - the Large and Small Magellanic Clouds - are clearly visible in the southern sky.
Why is there very little heavy elements in the matter of the oldest stars in the galaxy, while, on the contrary, in the matter of the youngest stars there is an increased content of them?
The oldest stars formed from a protogalactic gas cloud poor in heavy elements. Massive stars, rapidly evolving, exploded and enriched the gas of the protogalaxy with the heavy elements formed in them. Later generations of stars were formed from substances rich in metals.
What space objects resemble giant atomic nuclei? Could they be made of protons?
Neutron stars are mostly made of tightly packed neutrons. In this state, a neutron star can be considered as a giant atomic nucleus. A cosmic body cannot consist of protons alone, since gigantic repulsive forces will arise between them and the body will collapse.
How can strong X-ray emission occur on stars?
In a binary star system, one of the components may be a neutron star. The matter sucked in by this star accelerates to very high speeds in its vicinity. When a substance collides with a surface, energy is released in the form of x-rays. Such radiation can also occur when particles falling into a black hole collide with each other.
What cosmic bodies cannot be separated, while their fusion is possible?
Only black holes have these properties.
Where in space were the chemical elements that make up the human body formed?
The human body consists of 65% oxygen, 18% carbon, as well as nitrogen, magnesium, phosphorus and many other elements. In total, 70 chemical elements are found in living organisms. All elements heavier than hydrogen and helium, including iron, were synthesized during thermonuclear reactions in the interior of stars. Chemical elements heavier than iron were formed during supernova explosions.
How to prove that the Sun is and has always been close to the galactic plane?
Evidence that the Sun is close to the middle of the galactic disk is that the middle of the Milky Way almost coincides with the great circle of the celestial sphere. The Sun's velocity vector relative to the center of the galaxy also lies in the galactic plane. This indicates that the Sun has always moved in this plane.
Does the expansion of the Universe affect the distance of the Earth:
1) to the moon;
2) to the center of the Milky Way;
3) to the M 31 galaxy in the constellation Andromeda;
4) to the center of the local supercluster of galaxies?
Gravitationally bound systems (solar system, galaxy, clusters of galaxies) do not participate in cosmological expansion. Therefore, in the first three cases, cosmological expansion does not affect the distances between the Earth and these objects, but in the last, fourth, it does.
Is it possible to see the past of the Universe?
Anyone can do this by observing the starry sky. The farther stars or galaxies are from us, the longer the light travels from them and the more distant the past we can look into. For example, we see the closest star group to us, Alpha Centauri, as it was 4.3 years ago. And the Andromeda nebula looks like it did 2.5 million years ago.
Why do different cosmic objects have almost the same relative content of helium, but different contents of heavier elements?
Is the stellar Universe finite or infinite?
The boundary of the observable stellar Universe is located at a distance of about 13.4 billion light years from Earth. This is the distance light will travel in the time since the formation of the first stars. No stars have yet been discovered at distances further from us.
> What is a galaxy?
Find out, what is a galaxy: description of formation in the Universe, interesting facts with photos from Hubble, the Milky Way, sizes, number of stars and dark matter.
Surely you know that the solar system does not exist in isolation. Together with other stars, the Sun is located in . But what is a galaxy? In simple terms, this is a collection of stars gathered in a certain area with the help of gravitational force.
We've learned a lot about our home galaxy, so let's look at the concept through the Milky Way. It belongs to the spiral galaxy type and contains a bright core densely filled with stars. The remaining stars rotate around, creating a flattened disk. In total, there are 200-400 billion stars in the Milky Way. It has two spiral arms that extend beyond the core, as well as a kind of spiral pinwheel that extends to the outer edges. The width reaches 100,000 light years.
It is worth noting that the observed stars are only a small part of the entire galaxy. She is also surrounded by a giant halo. It cannot be seen, does not come into contact with ordinary matter, and does not produce a traceable type of radiation. But we can prove its presence, since it still affects other objects with gravity. If stars occupy approximately 580 billion solar masses, then dark matter can cover 6 trillion.
But our Milky Way galaxy is just one example. There are also elliptical ones, of which there are many more. This is where the largest representatives are found. For example, with 2.7 trillion stars. The smallest type is ultra-compact dwarf clusters, which are only slightly larger than globular clusters.
Stars are attracted and form galaxies, which also gather in clusters. At the top are superclusters capable of containing millions of galaxies and reaching hundreds of millions of light years in width. Now you can form an idea of what a galaxy is.
5 Amazing Facts About the First Galaxies in the Universe
One of the most amazing facts about the Universe is that it did not always exist. Everything we now observe came from tiny particles of matter that grew larger gravitationally and through collisions and mergers. When we look at distant objects, we see light that was emitted millions or billions of years ago (depending on the distance).
One day, technology will reach a level where we will see a Universe devoid of galaxies and stars. We're waiting for the James Webb Space Telescope to launch in 2018, but now we have a surprising five interesting facts about the most distant objects in the photo.
- In the beginning there were no rocky planets. A star emerges from molecular gas. Large gas clouds form in the cluster, turning into stars, and small worlds that become planets (from hydrogen and helium). But heavier elements appeared after the explosions of the first stars, which formed them during nuclear processes.
- Early galaxies were much smaller than modern ones. The first neutral atoms formed began to fuse into seeds of several million solar masses. After 50-200 million years, gravity caused them to collapse and create the first stars. Then gravity again forces them to merge into a cluster, increasing the intensity of the appearance of new young stars. This is how the first galaxies began to be created.
- No matter how hard the Hubble telescope tries, it is not powerful enough to see the very first galaxies. When they form, they are filled with hot, bright blue stars. But this light has to travel 13 billion years on its way to us. The expansion of space causes UV light to mix into the mid-IR region of the spectrum. Therefore, scientists are eagerly awaiting the launch of James Webb.
- The most massive stars existed in early times. If we now look into the ultramassive stellar territory, we can find the brightest and most massive stars. The largest nebula in our territory is the Tarantula, where the oldest star R136a1 lives. It is 250 times more massive than the sun and is created from primordial hydrogen and helium. But we will be able to achieve the scale of parameters with the launch of James Webb.
- The first supermassive black holes should have appeared in galactic centers from the moment of their birth. Surprisingly, the larger the star, the shorter its lifespan. The most massive objects live only a few million years, after which they die in the form of supernovae or collapse into a black hole. The latter rapidly move to galactic centers, where they grow to the supermassive type. Early galaxies are capable of containing holes that are 4 million times more massive than the Sun.
There are three main types of galaxies: spiral, elliptical and irregular. The first include, for example, the Milky Way and Andromeda. In the center are objects and a black hole, around which a halo of stars and dark matter revolves. Arms branch off from the core. The spiral shape is formed due to the fact that the galaxy does not stop rotating. Many representatives have only one sleeve, but some have three or more.
Table of characteristics of the main types of galaxies
Spiral ones come with or without a jumper. In the first type, the center is crossed by a dense bar of stars. And in the latter, such formation is not observed.
Elliptical galaxies contain the oldest stars and do not have enough dust and gas to create young ones. They may resemble a circle, oval or spiral type in shape, but without sleeves.
About a quarter of the galaxies are irregular groups. They are smaller than spiral ones and sometimes display bizarre shapes. They can be explained by the appearance of new stars or gravitational contact with a neighboring galaxy. Among the incorrect ones are .
There are also many galactic subtypes: Seyfert (fast-moving spirals), bright elliptical supergiants (absorbing others), ring supergiants (without a core), and others.