Many facts known today seem so familiar and familiar that it is difficult to imagine how we lived without them before. However, scientific truths for the most part did not arise at the dawn of mankind. This largely concerns knowledge about outer space. The types of nebulae, galaxies, and stars are known to almost everyone today. Meanwhile, the path to modern understanding was quite long. People did not immediately realize that the planet was part of the Solar System, and it was part of the Galaxy. Types of galaxies began to be studied in astronomy even later, when it was understood that the Milky Way is not alone and the Universe is not limited to it. as well as the general knowledge of space outside the “milk road”, became Edwin Hubble. Thanks to his research, we know a lot about galaxies today.
Types of galaxies in the Universe
Hubble studied nebulae and proved that many of them are formations similar to the Milky Way. Based on the collected material, he described what the galaxy looks like and what types of similar space objects exist. Hubble measured the distances to some of them and proposed its own classification. Scientists still use it today.
He divided all the many systems in the Universe into 3 types: elliptical, spiral and irregular galaxies. Each type is actively studied by astronomers around the world.
The piece of the Universe where the Earth is located, the Milky Way, belongs to the “spiral galaxy” type. Types of galaxies are identified based on differences in their shapes, which affect certain properties of the objects.
Spiral
The types of galaxies are not equally distributed throughout the Universe. According to modern data, spiral-shaped ones are more common than others. In addition to the Milky Way, this type includes the Andromeda Nebula (M31) and the galaxy in (M33). Such objects have an easily recognizable structure. If you look from the side at what such a galaxy looks like, the view from above will resemble concentric circles spreading across the water. Spiral arms radiate from a spherical central bulge called the bulge. The number of such branches varies - from 2 to 10. The entire disk with spiral arms is located inside a rarefied cloud of stars, which in astronomy is called a “halo”. The core of the galaxy is a cluster of stars.
Subtypes
In astronomy, the letter S is used to designate spiral galaxies. They are divided into types depending on the structural design of the arms and features of the general shape:
Galaxy Sa: the arms are tightly twisted, smooth and unshaped, the bulge is bright and extended;
galaxy Sb: the arms are powerful, clear, the bulge is less pronounced;
galaxy Sc: the arms are well developed, they have a ragged structure, the bulge is poorly visible.
In addition, some spiral systems have a central, almost straight bridge (called a “bar”). In this case, the letter B (Sba or Sbc) is added to the galaxy designation.
Formation
The formation of spiral galaxies appears to be similar to the appearance of waves from the impact of a stone on the surface of water. According to scientists, some kind of push led to the emergence of the sleeves. The spiral branches themselves represent waves of increased density of matter. The nature of the push can be different, one of the options is movement into stars.
The spiral arms are young stars and neutral gas (the main element is hydrogen). They lie in the plane of rotation of the galaxy, so it resembles a flattened disk. The formation of young stars is also possible at the center of such systems.
Nearest neighbor
The Andromeda Nebula is a spiral galaxy: a view from above reveals several arms emanating from a common center. From Earth, it can be seen with the naked eye as a blurry, foggy spot. Our galaxy's neighbor is somewhat larger in size: 130 thousand light years in diameter.
Although the Andromeda nebula is the closest galaxy to the Milky Way, the distance to it is enormous. It takes light two million years to travel through it. This fact perfectly explains why flights to a neighboring galaxy are so far only possible in science fiction books and films.
Elliptic systems
Let us now consider other types of galaxies. A photo of the elliptical system clearly demonstrates its difference from its spiral counterpart. Such a galaxy has no arms. It looks like an ellipse. Such systems can be compressed to varying degrees, and can be something like a lens or a sphere. There is practically no cold gas found in such galaxies. The most impressive representatives of this type are filled with rarefied hot gas, the temperature of which reaches a million degrees and above.
A distinctive feature of many elliptical galaxies is their reddish tint. For a long time, astronomers believed this to be a sign of the antiquity of such systems. They were thought to be mostly made up of old stars. However, research in recent decades has shown the fallacy of this assumption.
Education
For a long time, there was another hypothesis related to elliptical galaxies. They were considered the very first to arise, formed shortly after the Big Bang. Today this theory is considered outdated. German astronomers Alar and Yuri Thumre, as well as the American scientist Francois Schweitzer, made a great contribution to its refutation. Their research and discoveries in recent years confirm the truth of another hypothesis, the hierarchical model of development. According to it, larger structures were formed from fairly small ones, that is, galaxies did not form immediately. Their appearance was preceded by the formation of star clusters.
According to modern concepts, elliptical systems were formed from spiral-shaped arms as a result of the merger. One confirmation of this is the large number of “twisted” galaxies observed in remote areas of space. On the contrary, in the closest regions there is a noticeably higher concentration of elliptical systems, which are quite bright and extended.
Symbols
Elliptical galaxies also received their own designations in astronomy. They use the symbol “E” and numbers from 0 to 6, which indicate the degree of flattening of the system. E0 are galaxies with an almost regular spherical shape, and E6 are the flattest.
Raging Cannonballs
Elliptical galaxies include the systems NGC 5128 from the constellation Centaur and M87, located in Virgo. Their feature is powerful radio emission. Astronomers are primarily interested in the structure of the central part of such galaxies. Observations by Russian scientists and studies by the Hubble telescope show quite high activity in this zone. In 1999, American astronomers obtained data on the core of the elliptical galaxy NGC 5128 (constellation Centaur). There, there are huge masses of hot gas in constant motion, swirling around the center of what may be a black hole. There is no exact data on the nature of such processes yet.
Irregularly shaped systems
It is also located in the Large Magellanic Cloud. Here scientists have discovered a region of constant star formation. Some of the stars that make up the nebula are only two million years old. In addition, the most impressive star discovered in 2011, RMC 136a1, is also located here. Its mass is 256 solar.
Interaction
The main types of galaxies describe the features of the shape and arrangement of the elements of these cosmic systems. However, no less interesting is the question of their interaction. It's no secret that all space objects are in constant motion. Galaxies are no exception. Types of galaxies, at least some of their representatives, could be formed in the process of merger or collision of two systems.
If we remember what such objects are, it becomes clear how large-scale changes occur during their interaction. During a collision, a colossal amount of energy is released. Interestingly, such events are even more likely in the vastness of space than the meeting of two stars.
However, the “communication” of galaxies does not always end in a collision and explosion. A small system can pass through its large brother, disturbing its structure. This creates formations similar in appearance to elongated corridors. They consist of stars and gas and often become zones for the formation of new luminaries. Examples of such systems are well known to scientists. One of them is the Cartwheel galaxy in the constellation Sculptor.
In some cases, the systems do not collide, but pass by each other or only slightly touch. However, regardless of the degree of interaction, it leads to serious changes in the structure of both galaxies.
Future
According to scientists’ assumptions, it is possible that after some, quite a long time, the Milky Way will absorb its closest satellite, a relatively recently discovered system, tiny by cosmic standards, located at a distance of 50 light years from us. Research data suggests an impressive lifespan for this satellite, which will likely end during a merger with its larger neighbor.
Collision is a possible future for the Milky Way and the Andromeda Galaxy. Now the huge neighbor is separated from us by about 2.9 million light years. Two galaxies are approaching each other at a speed of 300 km/s. A probable collision, according to scientists, will occur in three billion years. However, today no one knows for sure whether it will happen or whether the galaxies will only slightly touch each other. For forecasting, there is not enough data on the characteristics of the movement of both objects.
Modern astronomy studies in detail such cosmic structures as galaxies: types of galaxies, features of interaction, their differences and similarities, the future. There is still a lot that is unclear in this area and requires additional study. The types of structure of galaxies are known, but there is no precise understanding of many details associated, for example, with their formation. The current pace of improvement of knowledge and technology, however, allows us to hope for significant breakthroughs in the future. In any case, galaxies will not cease to be the center of much research. And this is connected not only with the curiosity inherent in all people. Data about cosmic patterns and life make it possible to predict the future of our piece of the Universe, the Milky Way galaxy.
The size of the visible part of the Universe is simply amazing! However, this is just a grain of sand on the shore of the boundless Ocean - the Big Universe - the true size of which we are neither able to imagine nor calculate...
The Milky Way Galaxy is part of a family of neighboring galaxies known as the Local Group, and together with them forms a galaxy cluster. There are magnificent spirals among nearby galaxies. One of them, the Andromeda Galaxy, is the most distant object visible to the naked eye. Most galaxies in the Universe are either spiral or elliptical in shape, and many of them are part of galaxy clusters.
Throughout the 19th century. and at the beginning of the 20th century. astronomers did not know exactly what these foggy light spots were visible to them through the telescope. It was clear that stars were part of the Milky Way, as were bright gas clouds such as the Orion Nebula. But in their search for comets and planets, astronomers such as Charles Messier and William Herschel discovered thousands of fainter nebulae, many of them spiral. Astronomers wanted to know whether these were galaxies located far beyond the Milky Way, or just clouds of gas in our Galaxy. This question was answered only when a way was found to measure the distances to these faint nebulae.
In 1924, American astronomer Edwin Hubble convincingly proved that spiral nebulae are giant galaxies, similar to the Milky Way, but infinitely distant from it. With one blow he revealed the staggering enormity of the universe. Hubble was the first to discover variable stars in the Andromeda galaxy - Cepheids. They were much fainter than the Cepheids of the Magellanic Clouds. The difference in brightness meant that the Andromeda Galaxy should be 10 times farther from us than the Magellanic Clouds.
The Andromeda Galaxy can be seen with the naked eye - it is the most distant object that can be seen without binoculars or a telescope. Countless galaxies are much fainter than this one and therefore even more distant from us. Edwin Hubble discovered the kingdom of galaxies. Over the next few years, he measured the distances to many other spirals and was able to prove that even the nearest galaxies are distant from us by many millions of light years. The size of the observable Universe has far exceeded previous guesses.
Local group
As we peer into deep space, we discover that galaxies are not evenly distributed throughout the Universe. Galaxies group together to form clusters, or families. Our own family is called the "Local Group". It is, in general, a rather sparse formation: about 25 of its members are scattered over a space of 3 million light years. The largest of them are the Milky Way, as well as the spiral galaxies M31 in Andromeda and M3 in Triangulum. The Milky Way is accompanied by about nine dwarf galaxies moving nearby, and Andromeda has another eight. Astronomers continue to find more and more faint galaxies in our Local Group.
Each member of the Local Group moves under the gravitational pull of all other members. All galaxy clusters are held together by the gravitational field, which is the most important force acting in the Universe over large distances. By measuring the speeds of galaxies in the Local Group, astronomers can calculate its total mass. It is about 10 times greater than the mass of visible stars, which means that there must be a lot of dark, invisible matter in the Local Group.
Cluster in Virgo
If we continue our journey beyond the Local Group, we will encounter other small groups of galaxies - such as Stefan's Quintet, in which two spiral galaxies are locked together. And then much larger clusters flicker. The enormous Virgo Cluster, about 50 million light-years away, is the closest large cluster of galaxies to us. It is too distant for the distance to be calculated using variable stars. Instead, the magnitudes of the brightest stars and largest star clusters are used for calculations. Their brilliance is compared with the brilliance of similar objects, the distance to which is already known.
The Virgo Cluster is huge; it spreads over an area approximately 200 times larger than the area occupied in the sky by the full Moon! This gigantic cluster has several thousand members. In its central part there are three elliptical galaxies first listed by Charles Messier: M84, M86 and M87. These are truly huge galaxies. The largest of them, M87, is comparable in size to our entire “Local Group”. The Virgo Cluster is so massive that its gravitational pull not only holds this huge collective together, but also extends all the way to our “Local Group.” Our Galaxy and its companions are slowly moving towards the Virgo cluster.
Cluster in the constellation Coma Berenices
Moving even further, approximately 350 million light years away, we arrive at a huge galactic city in the constellation Coma Berenices. This is the Coma Cluster, containing more than 1,000 bright elliptical galaxies and perhaps many thousands of smaller members that can no longer be seen with modern means. The size of the cluster reaches 10 million light years across; two supergiant elliptical galaxies lie at its very core. Astronomers suspect that this cluster contains tens of thousands of members.
All galaxies are held in a cluster by gravitational forces. In this case, the velocities of galaxies within the cluster indicate that only a few percent of the total mass is contained in the stars that are visible to us. The Coma Cluster, like other large clusters of its type, consists primarily of dark matter.
The central regions of densely populated clusters like the one in Coma Berenices are unlikely to contain spiral galaxies. This may be because spiral galaxies that once existed there have merged together to form elliptical galaxies. The Coma Cluster is a strong source of X-rays emitted by very hot gas with temperatures ranging from 10 to 100 million degrees. This gas was found in the central part of the cluster; in its chemical composition it is close to the material of stars.
It is possible that the following happened. The galaxies located in the central part of the cluster collided with each other and, scattering after the impact, shed their gas clouds. The gas was heated by friction as galaxies rushed through it at speeds of up to thousands of kilometers per second. As the galaxies lost their gas, their spiral arms gradually disappeared.
Superclusters and voids
Photographing deep space shows that as we move into the Universe, galaxies keep appearing and appearing. Almost every direction we look reveals a scattering of faint galaxies, like dust. Some objects were detected at a distance of up to 10 billion light years. Each of these countless galaxies contains billions of stars. Even professional astronomers find it difficult to imagine such numbers. The extragalactic Universe is larger than anything imaginable.
Almost all galaxies are found in clusters containing from a few to many thousands of members. But what can be said about these clusters themselves: maybe they are also grouped into families? Yes, that's exactly it!
The Local Cluster of Clusters, known as the Local Supercluster, is a flattened formation that includes, among others, the Local Group and the Virgo Cluster. The center of mass is located in the Virgo cluster, and we are on the outskirts. Astronomers have made efforts to map the Local Supercluster in three dimensions and reveal its structure. It turned out to contain about 400 individual galaxy clusters; these clusters are collected in layers and stripes, separated by intervals.
Another supercluster is located in the constellation Hercules. It is about 700 million light years away, and for about 300 million light years on the way to it, galaxies apparently do not meet at all.
Thus, astronomers have established that superclusters are separated from each other by giant empty spaces. Inside superclusters there are also “bubbles” millions of light years in size that do not contain galaxies. Superclusters fold into threads and ribbons, giving the Universe, on its grandest scale, a spongy structure.
Hubble's Law and Redshift
Now we know that our Universe is expanding all the time, becoming larger and larger. Hubble played a decisive role in the discovery. Using Cepheid stars, he determined the distances to the nearest galaxies, and from redshift measurements he determined their velocities. The discovery was made when he plotted the speeds of galaxies against their distances. It turned out that the relationship between these two quantities is expressed on the graph by a straight line: the farther the galaxy is from us, the greater its speed. Hubble's Law States that the faster a galaxy moves, the more distant it is. Hubble found a connection between two quantities that could be measured for nearby galaxies: between distance and redshift (which gives speed). And after such a connection is established, Hubble's law can be reversed and used for the reverse procedure. By measuring the redshift for more distant galaxies, it is possible, using Hubble's law, to calculate the distance to them. This is how astronomers find out the distances to distant galaxies in our Universe.
Of course, when using Hubble's law, there is some uncertainty about the correctness of the result. For example, if there is an inaccuracy in calculating the distances to nearby galaxies, the graph will no longer be absolutely correct: any error in it will continue into deep space when we try to use it to find out the distances to more distant galaxies. However, Hubble's law is the most important method for studying the large-scale structure of the Universe.
Expansion of the Universe
Why does it follow from Hubble's law that the Universe is expanding? All galaxies are running away from us. So the Milky Way is at the center of the Universe? After all, when we see an explosion - for example, fireworks exploding in the sky - then everything scatters in all directions from the place of the explosion. So, if everything around us is flying away from us, we must be at the center of this expansion?
No, that's not true: we are not in the center.
When, during an explosion, individual parts fly apart in different directions, the distances between all the fragments increase. This means that each fragment “sees” how all the others fly away from it. To see how this works, take a balloon and draw some galaxies on it using spiral and elliptical symbols. Now slowly inflate the balloon. As it expands, galaxies move away from each other. Whatever galaxy you choose as your starting point, all the others, as the balloon inflates, disperse further and further.
This can also be discussed from a mathematical point of view. The shell of the ball is a curved surface, it has almost no thickness. When you inflate a balloon, this spherical surface stretches to cover more and more of the space. The curved shell, being itself two-dimensional, expands in three-dimensional space. And as this happens, the galaxies drawn on the ball move further and further away from each other.
As for the Universe, the three dimensions of ordinary space expand into a special four-dimensional space called space-time. The additional dimension is time. Over time, the three dimensions of space continuously increase their extent. Clusters of galaxies, inextricably linked to expanding space, are constantly moving away from each other.
Age of the Universe
How can astronomers determine the age of the Universe? We find out the age of a tree by counting the annual rings on a cut - one ring grows per year. Geologists can estimate the age of rocks deposited in sediments by the fossils found in them. The age of the Moon was determined by measuring the radioactivity of rocks containing radioactive elements. In all of these methods, one way or another, the necessary data is obtained - the number of rings, the saw fossils, the intensity of the remaining radiation - and with their help the age is calculated.
To determine the age of the expanding Universe, we study the distances and velocities of a large number of galaxies. It turns out that for every million light years the speed of galaxies increases by about 20 km/s (astronomers do not know this number quite accurately, with a tolerance of 2-3 km/s). Knowing how speed changes with distance, we can calculate that 17 billion years ago all matter was in the same place. This is one of the ways to determine the age of the Universe. Since her age is the time that has passed since the Big Bang, when expansion began...
For more information about the real structure of the Universe, see the books of Academician N.V. Levashov “The Last Appeal to Humanity” and “Heterogeneous Universe” and others.
A remote galaxy cluster is home to 800 trillion Suns.
Ivan Terekhov, 10/17/2010
The infinite space “throws” more and more new, impressive details of existence at the early stage of its development to scientists. This time, astronomers from the Harvard-Smithsonian Center for Astrophysics, working with the SPT (South Pole Telecope) telescope, discovered one of the most massive galaxy clusters, 7 billion light years away from us. Information about the total mass of the cluster can cause attacks of dizziness and nausea when trying to assess the scale of the action: according to measurements, the star cluster has a mass equal to the mass 800 trillion suns.
The cluster, called SPT-CL J0546-5345, located in the constellation Pictor. Its redshift z is 1.07, meaning that astronomers are now observing the cluster in the state it was in seven billion years ago. Moreover, even then this structure was almost as large as the Coma Berenices cluster, which is one of the densest clusters known to science. Researchers believe that over time SPT-CL J0546-5345 could have quadrupled.
“This cluster of galaxies wins the heavyweight title. This is one of the most massive clusters ever found at this distance,” said center employee Mark Brodwin (Mark Brodwin), one of the authors of the article published in "Astrophysical Journal". As Brodwin noted, in SPT-CL J0546-5345 there are many quite old galaxies. This means that the cluster arose in the “childhood” of the Universe, in the first two billion years of its existence. Age of the Universe, according to the probe WMAP (Wilkinson Microwave Anisotropy Probe), is estimated to be 13.73 billion years old. Such clusters can be useful in studying the influence of dark matter and dark energy on the formation of various structures in space.
The team discovered the cluster by working with early data from the SPT telescope at Amundsen-Scott Station in Antarctica. The 10-meter telescope, operating in the frequency range 70-300 GHz, began operation in 2007. Searching for galaxy clusters is its main task; with the help of SPT data, scientists hope to get closer to obtaining the equation of state for dark energy, which, according to astronomers, accounts for about 74% of the mass of the Universe. Astronomers studied the discovered cluster using instruments of the Spitzer Space Telescope. (Spitzer Space Telescope), as well as a group of telescopes at the Chilean Las Campanas Observatory. This made it possible to identify individual galaxies in the cluster and estimate the speed of their movement.
SPT-CL J0546-5345 was discovered thanks to the so-called Sunyaev-Zeldovich effect - minor distortions in the cosmic microwave background radiation, the “echo” of the Big Bang, that occur when radiation passes through a large cluster. This search method is equally good at identifying both nearby and distant clusters, and also makes it possible to fairly accurately estimate their mass.
Follow us
We live in a galaxy called the Milky Way, an empire consisting of hundreds of billions of people. How did we get here? What does the future hold for us? These questions are inseparable from the concept of a galaxy. Our universe contains two hundred billion galaxies, all of them are unique, huge and constantly changing. Where do galaxies come from? How are they built? What is their future? And how will they die?
This is our Milky Way galaxy, about twelve billion years old. The galaxy is a giant disk with huge spiral arms and a glow in the center; there are countless such galaxies in space. The galaxy is a large cluster of stars, on average it numbers a hundred billion stars. This is a real stellar incubator, a place where stars are born and where they die. Stars in a galaxy emerge from clouds of dust and gas called nebulae. Our galaxy contains billions of stars, many of which are surrounded by planets and 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 his time with a lens diameter of 254 centimeters. In the night sky, he saw unclear clouds of light that were very far from us, the scientist came to the conclusion that these were not individual stars, but entire star cities, galaxies far beyond the Milky Way.
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, it has two spiral arms and it has about one hundred and sixty million stars. Galaxy M-87 is a giant ellipse; it is one of the oldest galaxies in the universe and the stars in it emit golden light.
Galaxies are huge, real giants, on earth distances are measured in kilometers, in space astronomers use a unit of length, a light year, the distance traveled by light in one year, they are approximately equal to nine and a half trillion kilometers.
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 200,000 light years, twice the size of our Milky Way. M 87 is the largest galaxy in nearby space, it is much larger than Andromeda, but compared to the giant AC 1011, it seems completely tiny. AC 1011 is 6,000,000 light years wide and is the largest known galaxy, 60 times larger than the Milky Way.
So, we know that galaxies are huge and they are everywhere, but where did they come from? To create stars you need gravity, to unite stars into galaxies you need even more. The first stars appeared just 200,000,000 years after the big bang, then gravity pulled them together and the first galaxies appeared.
Galaxies have existed for more than twelve billion years, we know that these vast empires of stars take a variety of forms from vortex spirals to huge balls of stars, but still much in the galaxies remains a mystery to us.
Young galaxies are formless accumulations of gas and dust stars; only after billions of years do they turn into structures such as a vortex galaxy. The force of gravity gradually pulls the stars together, they rotate faster and faster until they take the form of a disk, then the stars and gas form giant spiral arms, this process has been repeated billions of times in the vastness of space. Each galaxy is unique, but they all have one thing in common: they all revolve around their center. For years, scientists wondered what had enough power to change the behavior of a galaxy, and finally, the answer was found: a black hole and not just a black hole, but a super massive black hole. Super massive black holes feed on gas and stars, sometimes the black hole consumes them too greedily and the food is thrown back into space as a beam of pure energy. The black hole at the center of the Milky Way is gigantic, 24,000,000 kilometers wide. Planet earth is located at a distance of twenty-five thousand light years from the center of the milky way, which is many billions of kilometers. 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 galaxies. According to all the laws of physics, galaxies should decay, why doesn’t this happen? There is a force in space that is more powerful than a super massive black hole, it cannot be seen and is almost impossible to calculate, but it exists, it is called dark matter and it is everywhere. It seems that the galaxies exist separately, there are trillions of kilometers between them, but in fact the galaxies are united into groups, a cluster of galaxies. Clusters of galaxies form superclusters containing tens of thousands of galaxies. Galaxies not only change, but also move; it happens that galaxies collide with each other and then one absorbs the other; the collision of galaxies lasts millions of years and eventually two galaxies merge into one. Similar collisions occur everywhere in space, and our galaxy is no exception. Our galaxy is moving towards another galaxy, the Andromeda nebula, and this does not bode well for our galaxy. The Milky Way is approaching Andromeda at a speed of 250,000 miles per hour, which means that in five to six billion years our galaxy will no longer exist. Oddly enough, when galaxies collide, the stars will not collide with each other; they are still too far from each other; they will simply get mixed up. However, the dust and gas between the stars will begin to heat up, at some point they will ignite, and the two colliding galaxies will become white hot. The inhabitants of planet “earth” were incredibly lucky; life originated on our planet only due to the fact that our solar system is located in the right part of the galaxy; if we were located a little closer to the center, we would not have survived.
Our galaxy and many other galaxies in the universe pose before us a bunch of questions that require answers and secrets that have not yet been discovered by anyone. It is in galaxies that the key to understanding the universe lies.
Galaxies are born, break up, collide and die; galaxies are superstars for the world of science.
» 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 on 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.
Looking into the night starry sky, we can see a wide strip completely strewn with stars: bright and barely noticeable, white and blue, reddish and green. The ancient Greeks called this cluster of stars Galaxy, which in Russian means .
Milky Way in the night sky
If you look at this star system from somewhere from the outside, from outer space, you would notice that it resembles an oblate ball filled with 150 billion stars. The size of our Galaxy is so large that it is difficult to imagine. From one edge to the other, a light beam travels about 100 thousand Earth years!
This is what our Galaxy looks like
At the center of our Galaxy there is a core, from which extend several huge spiral branches filled with stars. Our Sun is located at a distance of 30 thousand light years from the core of the Galaxy, in one of its spiral arms. That is, it is located on the outskirts of the Galaxy.
Position of the Sun in the Galaxy
Stars in the Galaxy, despite their apparent “density,” are located quite sparsely. For example, in the vicinity of the Sun, the average distance between the nearest stars is approximately 10 million times greater than their own diameters.
Thus, the stars in the Universe are not scattered randomly. They are grouped into ordered systems in which they are connected to each other by the force of gravity (attraction). Such star systems are called galaxies. In addition to stars, galaxies also contain interstellar dust and gas.
There are other galaxies in the Universe. The closest ones to our star system are about 150 thousand light years away from us. In the sky of the Southern Hemisphere they are visible as small foggy spots.
These star clusters were first described in detail by Magellan's satellite Pigafetta during his famous voyage around the world. They entered into astronomy under the name of the Magellanic Clouds - Large and Small.
One of the closest galaxies to us is Andromeda's nebula. It is one of the largest star systems in our region of the Universe. It can be observed even with ordinary binoculars, and in good weather - with the naked eye.
Galaxies have a wide variety of shapes and structures. There are spherical and elliptical, disk-shaped, spiral-shaped, like ours, and irregularly shaped galaxies.
In the part of the Universe accessible to modern means of astronomical research, there are billions of galaxies. Astronomers called their collection Metagalaxy.