Guide to the Universe: who is who

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Guide to the Universe: who is who
Guide to the Universe: who is who
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There are many amazing things in our Universe, and sometimes it seems more interesting than the most sophisticated inventions of science fiction writers. And now we want to talk about objects in deep space (both real and assumed), which everyone has heard about, but not everyone imagines.

Black hole

Red giant

There are many different stars: some are hotter, others are colder, some are large, others (conventionally) small. The red giant star has a low surface temperature and a huge radius. Because of this, it has a high luminosity. The radius of the red giant can reach 800 solar, and the brightness can exceed the solar one by 10 thousand times. Aldebaran, Arcturus, Gakrux are red giants included in the list of the brightest luminaries of the night sky. At the same time, red giants are not the most massive. The largest stars are red supergiants: their radius can exceed the solar one by 1500 times.

The red giant is the final stage in the evolution of a star. A star becomes a red giant when at its center all the hydrogen is converted into helium, and the thermonuclear combustion of hydrogen continues at the periphery of the helium core. Thus, all red giants have a similar structure: a hot dense core and a very rarefied and extended shell. This leads to an increase in luminosity, expansion of the outer layers and a decrease in surface temperature. And also to the intense stellar wind - the outflow of matter from the star into interstellar space.

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The further fate of the red giant depends on the mass. If the mass is low, then the star will transform into a white dwarf; if it is high, it will turn into a neutron star or black hole.

White dwarf

A dwarf star is the exact opposite of a giant star. Before us is an evolved luminary, the mass of which is comparable to the mass of the Sun. Moreover, the radius of white dwarfs is about 100 times smaller than the radius of our star. They are "born" when the red giants "shed" their shell, which scatters in the form of a planetary nebula in interstellar space. The remaining cold and almost non-emitting helium core is called a white dwarf.

White dwarfs occupy 3-10% of the stellar population of our Galaxy, but due to their low luminosity it is very difficult to identify them. An "elderly" white dwarf is no longer directly white. The name itself comes from the color of the first open stars, for example Sirius B (its size, by the way, can be quite comparable with the size of our Earth). In fact, a white dwarf is not a star at all, since thermonuclear reactions no longer take place in its interior. Simply put, a white dwarf is not a star, but its "corpse".

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With further evolution, the white dwarf cools even more, and its color changes from white to red. The final stage in the evolution of such an object is a cooled black dwarf. Another option is the accumulation of matter on the surface of the white dwarf, "overflowing" from another star, compression and subsequent explosion of a new or supernova.

Yellow dwarf

Not everyone knows about this type of stars. And this is strange, because our own Sun is a typical yellow dwarf. Yellow dwarfs are small stars with a mass of 0.8–1.2 solar masses. These are the luminaries of the so-called main sequence. In the Hertzsprung-Russell diagram, this is the area that contains stars that use the thermonuclear reaction of fusing helium from hydrogen as an energy source.

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Yellow dwarfs have a surface temperature of 5000–6000 K, and their average lifetime is 10 billion years.Such stars turn into red giants after their supply of hydrogen is burned up. A similar fate awaits our Sun: according to scientists' forecasts, in about 5-7 billion years it will engulf our planet, becoming a red giant, and then turn into a white dwarf. But long before all this, life on our planet will be burned.

Brown dwarf

A brown (or brown) dwarf is a very unusual dark red or even infrared object that is difficult to classify in any way. It occupies an intermediate position between a star and a gas planet. Brown dwarfs have a mass equal to 1–8% of the solar mass. They are too massive for planets, and gravitational compression makes it possible for thermonuclear reactions with the participation of "easily combustible" elements. But there is not enough mass to "ignite" hydrogen, and the brown dwarf shines for a relatively short time in comparison with an ordinary star.

The surface temperature of a brown dwarf can be 300–3000 K. It cools down continuously throughout its life: the larger such an object, the slower this process takes place. Simply put, a brown dwarf, due to thermonuclear fusion, heats up at the first stage of its life, and then cools down, becoming like an ordinary planet.

Brown dwarfs can form both in the protoplanetary disk of a star, and independently of other space objects. Planets can also appear around them and, according to some ideas, even inhabited ones. But since brown dwarfs emit little heat and for a very short time, the habitat zone is located quite close to them and disappears very quickly. If on Earth it took 3.5 billion years for the emergence of multicellular life, and the period of its further existence, given a successful coincidence of circumstances, is quite long, then, for example, multicellular life on such a planet near a brown dwarf with a mass of 0.04 solar will last no more than 0.5 billion years. Then, as the dwarf cools, the habitable zone will approach it, and all life on the planet will perish.

Double star

A binary star (or binary system) refers to two gravitationally bound stars that revolve around a common center of mass. The binary star seems to be a very exotic phenomenon, but it is very common in the Milky Way galaxy. Researchers believe that about half of all stars in the Galaxy are binary systems. Sometimes you can even find systems that consist of three stars.

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An ordinary star forms as a result of the compression of a molecular cloud due to gravitational instability. In the case of a double star, the situation is similar, but as for the reason for the separation, here scientists cannot come to a common opinion.

Supernova

A supernova is a phenomenon in which the brightness of a star increases by 4-8 orders of magnitude, and then gradually decreases. This is due to the explosion of the star, in which it is completely destroyed. Such a star overshadows other stars for some time: and this is not surprising, because when it explodes, its luminosity can exceed the solar one by 1 billion times. In galaxies comparable to ours, the appearance of one supernova is recorded approximately once every 30 years. However, stardust interferes with the observation of the object, because during the explosion, a huge volume of matter enters interstellar space. The leftover matter can act as a building material for a neutron star or black hole. Our star and the planets of the solar system originated in a giant cloud of molecular gas and dust. Approximately 4.6 billion years ago, the cloud began to compress, and for the first hundred thousand years after that, the Sun was a collapsing protostar. Over time, it stabilized and took on its present appearance.

There are two main types of supernovae.

Type I has no hydrogen in the optical spectrum. Therefore, scientists believe that such supernovae originated from the explosion of a white dwarf.After all, he, as we have already said, does not have hydrogen. Such white dwarfs must necessarily be part of a binary star. At a certain moment, matter from the second star begins to "pump" onto the white dwarf, and when it reaches its critical mass, a collapse occurs. Type I supernovae explode in both elliptical and spiral galaxies.

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In type II supernovae, researchers record hydrogen in the spectrum. Hence the assumption arises that we are talking about the explosion of an "ordinary" star. When the "fuel" in a massive (more than 10 solar masses) star is depleted, its formed core can reach a critical mass and collapse. In this scenario, the core of a Type II supernova ultimately becomes a neutron star. Such supernovae appear only in spiral galaxies.

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Neutron star

A neutron star consists mainly of neutrons - heavy elementary particles that do not have an electric charge. As already mentioned, the reason for their formation is the gravitational collapse of normal stars. Due to attraction, the stellar masses begin to pull towards the center until they become incredibly compressed. As a result, the neutrons are packed, as it were. Such an object has a thin atmosphere of hot plasma, an outer crust of ions and electrons, an inner crust of electrons and free neutrons, and an outer and inner core of densely packed neutrons. Many neutron stars rotate very rapidly - up to hundreds of revolutions per second.

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A neutron star is small - usually its radius does not exceed 20 km. Moreover, the mass of most of these objects is 1, 3–1, 5 solar (the theory assumes the existence of neutron stars with a mass of even 2.5 solar masses). The density of a neutron star is so great that one teaspoon of its substance weighs billions of tons.

Pulsar

Pulsars are neutron stars that emit radio, gamma, optical and X-rays, which are recorded by instruments in the form of pulses. The axis of rotation of such a star does not coincide with the axis of its magnetic field. And the pulsar radiates just along the latter - from its magnetic poles. And since the star rotates on its axis, we on Earth can observe radiation only at the moment when the pulsar turns its magnetic pole towards our planet. This can be compared to a lighthouse: it seems to the observer on the shore that he periodically blinks, although in reality the searchlight simply turns in the other direction. In other words, we observe some neutron stars as pulsars because one of their magnetic poles turns out to be directed towards the Earth as it rotates.

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The best studied pulsar is PSR 0531 + 21, which is located in the Crab Nebula at a distance of 6,520 light years from us. This neutron star makes 30 revolutions per second, and its total radiation power is 100,000 times higher than that of the Sun. However, many aspects related to pulsars remain to be studied.

Quasar

Pulsar and quasar are sometimes confused, but the difference between them is very large. Quasar is a mysterious object, whose name comes from the phrase "quasi-stellar radio source". Such objects are some of the brightest and most distant from us. In terms of radiation power, a quasar can exceed all the stars of the Milky Way combined by a hundred times.

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Of course, the discovery of the first quasar in 1960 sparked incredible interest in the phenomenon. Scientists now believe that the quasar is the active nucleus of the galaxy. There is a supermassive black hole pulling on itself matter from the space that surrounds it. The mass of the hole is simply gigantic, and the radiation power exceeds the radiation power of all stars located in the galaxy. The closest quasar to us is located at a distance of 2 billion light years, and the most distant, due to their incredible visibility, we can observe at a distance of 10 billion light years.

Blazar

Blazars are quasars that emit powerful plasma beams (the so-called relativistic jets) that can be seen by an observer from Earth. Two rays emanate from the core of the blazar and are directed in opposite directions. These streams of radiation and substances can destroy all living things in their path. If such a ray passes at a distance of at least 10 sv. years from the Earth, there will be no life on it.

The name itself comes from the words "quasar" and "BL Lizards". The latter is a characteristic representative of the blazar subtype known as the BLAZARTIDA. This class is distinguished by the features of the optical spectrum, which is devoid of broad emission lines characteristic of quasars.

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Now scientists have figured out the distance to the most distant blazar PKS 1424 + 240: it is 7.4 billion light years.

Black hole

Without a doubt, this is one of the most mysterious objects in the universe. Much has been written about black holes, but their nature is still hidden from us. The second cosmic speed (the speed required to overcome the gravity of a celestial body and leave the orbit around it) for them exceeds the speed of light! Nothing can escape the gravity of a black hole. It is so huge that it practically stops the passage of time.

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A black hole forms from a massive star that has used up its fuel. A star that collapses under its own weight and carries along the space-time continuum around it. The gravitational field becomes so strong that even light can no longer escape from it. As a result, the region in which the star was previously located becomes a black hole. In other words, a black hole is a curved section of the universe. He sucks in the matter located nearby. The first key to understanding black holes is believed to be Einstein's theory of relativity. However, the answers to all the basic questions have yet to be found out.

Mole Hole

Continuing the topic, one simply cannot pass by a purely hypothetical object - the so-called wormholes, or wormholes. They are represented as space-time tunnels, consisting of two entrances and a throat. A wormhole is a topological feature of space-time that allows (hypothetically) travel by the shortest path of all. To understand at least a little the nature of a wormhole, you can roll a piece of paper (symbolizing our space-time), and then pierce it with a needle. The resulting hole will be like a wormhole. If we move along the surface of a sheet from one hole to another (which in our reality is the only thing we can do), it will take a long way, but hypothetically, after all, it is possible to go through the hole and immediately find ourselves on the other side!

At different times, experts have put forward different versions of wormholes. The possibility of the existence of something like this proves the general theory of relativity, but so far it has not been possible to find a single wormhole. Perhaps, in the future, new studies will help confirm the existence of such objects.

Nebula

A nebula is nothing more than a cosmic cloud, which is composed of dust and gas. She is the main building block of our Universe: from it stars and stellar systems are formed. The nebula is one of the most beautiful astronomical objects that can glow with all the colors of the rainbow.

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The Andromeda Nebula (or Andromeda Galaxy) is the closest galaxy to the Milky Way. It is located at a distance of 2.52 million sv. years from Earth, much larger than our Galaxy and contains about 1 trillion stars. Perhaps humanity will reach the Andromeda Nebula in the distant future. And even if this does not happen, the Nebula itself will "come to visit", engulfing the Milky Way in 5 billion years.

It is important to clarify here. The word "nebula" has a long history: it used to be used to designate almost any astronomical object, including galaxies. For example, the Andromeda Nebula galaxy.Now they have moved away from this practice, and the word "nebula" denotes accumulations of dust, gas and plasma.

There is an emission nebula (a cloud of high temperature gas), a reflection nebula (not emitting its own radiation), a dark nebula (a dust cloud that blocks light from objects located behind it) and a planetary nebula (a shell of gas produced by a star at the end of its evolution). This also includes supernova remnants.

Dark matter

This is a hypothetical phenomenon that does not emit electromagnetic radiation and does not directly interact with it. Therefore, we cannot detect it directly, but we see signs of the existence of dark matter when observing the behavior of astrophysical objects and the gravitational effects they create.

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How did you find dark matter? Researchers calculated the total mass of the visible part of the Universe, as well as gravitational indicators, and identified a certain imbalance, which they attributed to a mysterious substance. They also found out that some galaxies rotate faster than they should according to calculations. Consequently, something influences them and does not allow them to "fly away" to the sides.

Scientists now believe that dark matter cannot be composed of ordinary matter, and that it is based on tiny exotic particles. But some doubt this, arguing that dark matter can also be composed of macroscopic objects.

Dark energy

If there is anything more mysterious than dark matter, it is dark energy. Unlike the first, dark energy is a relatively new concept, but it has already managed to turn our understanding of the Universe upside down. Dark energy, according to the findings of scientists, is something that causes our universe to expand with acceleration, that is, over time, more and more. Based on the hypothesis of dark matter, the mass distribution in the Universe looks like this: 74% is dark energy, 22% is dark matter, 0.4% is stars and other objects, 3.6% is intergalactic gas.

If in the case of dark matter there is at least indirect evidence of its existence, then dark energy exists purely within the framework of a mathematical model that considers the expansion of our Universe. Therefore, no one can now say with certainty what dark energy is.

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