What is black dwarf. Types of star

Black dwarf is a white dwarf, which has cooled to the temperature of the relict radiation (cosmic microwave background), and therefore became invisible. Unlike red dwarfs, brown dwarfs and white dwarfs, black dwarfs are hypothetical objects in the universe.

When a star evolved into white dwarf, she no longer had a heat source and shone only because everything was still hot. As if something was taken out of the oven. If you leave the white dwarf at rest, over time it will cool down to a temperature surrounding it. Unlike today's dinner, which cools off the convection, thermal conductivity and radiation, white dwarf is cooled only through radiation.

Since the pressure of the electron degeneration stops it from the collapse, which will lead to, white dwarf is a fantastic heat conductor (Fermi's physics explains the conductivity of both white dwarfs and metals!). How quickly cool white dwarf is easily calculated ... This depends only on the initial temperature, mass and composition (most of them consist of carbon and oxygen; some are predominantly of oxygen, neon and magnesium; others from helium). And at least some of the white dwarf core can crystallize, the cooling curve will have a small bump in this place.

Not black dwarf ... while still. White Dwarf Sirius B.

The universe is only about 13.7 billion years, therefore even a white dwarf, formed by 13 billion years ago (which is unlikely; which became white dwarfs, it took a billion years or so), there would have been still a temperature of several thousand degrees. The coldest white dwarf, observed today, has a temperature of a little less than 3000 Kelvin. He is waiting long way Before he becomes black dwarf.

It turns out, answer the question how much time will be needed by white dwarf to cool down to the temperature of the relict radiation, quite difficult. Why? Because there are many interesting effects that may be important, the consequences of their scientists have not yet been modeled. For example, white dwarf will contain a bit, and some part of it can decay through the time intervals in quadrillion years, generating heat. The substance is also not forever, protons can also disintegrate, generating heat. And relic radiation becomes colder with time, since.

In any case, if we say it is conditionally that the white dwarf, having a temperature of 5 Kelvin, becomes black dwarf, then it will be required at least 10 15 years to become black dwarf.

Something else does not happen white dwarfs singles; some have companions, forming together, for example, others can wander in a gas-pepped cloud ... the incident mass also generates heat, and if a sufficient amount of hydrogen is accumulated on the surface, then this star can be broken as h-bomb (This is called), a little heated white dwarf.

Name you read articles "Star Black Dwarf".

In the universe there are many different stars. Large and small, hot and cold, charged and not charged. In this article we will call the main types of stars, and also give detailed feature Yellow and white dwarfs.

1. Yellow dwarf. Yellow dwarf - type not big stars the main sequencehaving a lot of 0.8 to 1.2 mass of the Sun and the surface temperature of 5000-6000 K. For more information about this type of stars, see below.
2. Red giant. Red giant is a large star of reddish or orange. The formation of such stars is possible both at the stage of star formation and in the later stages of their existence. The largest giants turn into red supergigants. The star called Bethelgeuse from the Constellation Orion is the brightest example of red supergigant.
3. White Dwarf. White dwarf is what remains of the usual star with a mass that does not exceed 1.4 solar masses, after it passes the stage of the red giant. For more information about this type of stars, see below.
4. Red Dwarf. Red dwarfs are the most common starry-type objects in the universe. Assessment of their number varies in the range from 70 to 90% of the number of all stars in the galaxy. They are quite different from other stars.
5. Brown Dwarf. Brown dwarf - subsidences (with the masses in the range of approximately 0.01 to 0.08 mass of the Sun, or, respectively, from 12.57 to 80.35 masses of Jupiter and a diameter of approximately equal to the diameter of Jupiter), in the depths of which, in contrast From the stars of the main sequence, the reaction of thermonuclear synthesis is not occurring with the conversion of hydrogen in helium.
6. Subcaric dwarfs. Subcaric dwarfs or brown subcarlics are cold formations, by mass underlying the limit of brown dwarfs. Their mass is less than about one cell mass of the Sun or, respectively, 12.57 masses of Jupiter, the lower limit is not defined. They are more commonly considered by the planets, although to the final conclusion about what to consider the planet, and what - by subcaric dwarf, the scientific community has not yet come.
7. Black Dwarf. Black dwarfs - cooled and as a result, which are not emitted in the visible range of white dwarfs. It is the final stage of the evolution of white dwarfs. The masses of black dwarfs, like the masses of white dwarf, are limited from above 1.4 masses of the sun.
8. Double Star. Double Star - these are two gravitational related stars appearing around general Center masses.
9. New star. Stars whose luminosity suddenly increases 10,000 times. The new star is a double system consisting of white dwarf and companion stars located on the main sequence. In such systems, gas from the star gradually flows onto white dwarf and periodically explodes there, causing an outbreak of luminosity.
10. In excess of new star . The supernova star is a star that ends up its evolution in a catastrophic explosive process. The flash can be several orders of magnitude more than in the case of a new star. Such a powerful explosion is a consequence of the processes occurring in the star at the last stage of evolution.
11. Neutron Star. Neutron stars (NZ) are star formations with masses of about 1.5 solar and dimensions, noticeable smaller white dwarfs, about 10-20 km in diameter. They consist mainly of neutral subatomic particles - neutrons, tightly compressed gravitational forces. In our galaxy, according to scientists' estimates, there may be from 100 million to 1 billion neutron stars, that is, somewhere on one to one thousand ordinary stars.
12. Pulsary. Pulsary - Space sources of electromagnetic emissions coming to the ground in the form of periodic bursts (pulses). According to the dominant astrophysical model, the pulsars are rotating neutron stars with magnetic fieldwhich is tilted to the axis of rotation. When the Earth enters the cone formed by this radiation, then the radiation pulse can be fixed, repeating through the time intervals equal to the period of the stars. Some neutron stars make up to 600 revolutions per second.
13. Cefeida. Cefeida - class of pulsating stars with a fairly accurate dependence of the luminosity, named after the star Delta Cefhea. One of the most famous cefeid is a polar star. The list of the main types (types) stars with their brief characteristicOf course, does not exhaust the entire possible manifold of stars in the universe.

Yellow dwarf

Being at various stages of their evolutionary DevelopmentThe stars are divided into normal stars, the stars of dwarfs, the stars giants. Normal stars, this is the stars of the main sequence. Such, for example, belongs to our sun. Sometimes such normal stars are called yellow Dwarfs.

Characteristic

Today we will briefly tell about the yellow dwarfs, which are also called yellow stars. Yellow dwarfs are, as a rule, the stars of the middle mass, the luminosity and surface temperature. They are the stars of the main sequence, located approximately in the middle on the Herzshprung chart - Russell and following the colder and less massive red dwarfs.

According to the spectral classification of Morgan-kina, the yellow dwarfs correspond in the main class of the luminosity G, however, in transition variations, sometimes class K (orange dwarfs) or class F in the case of yellow-white dwarfs.

The mass of yellow dwarfs is often between 0.8 to 1.2 mass of the sun. At the same time, the temperature of their surface is one of its most from 5 to 6 thousand degrees on Kelvin.

The brightest and most importantly known representative from among the yellow dwarfs is our sun.

In addition to the sun, among the nearest yellow carlikov, it is worth noting:

1. Two components in the Triple Alfa Centauri system, among which alpha centaurus A according to the luminosity spectrum is similar to the Sun, and Alpha Centauro B - the typical orange dwarf class K. The distance to both components is just over 4 light years.
2. Orange Dwarf - Star of the Russian Academy of Sciences, she is Epsilon Eridan, with the class of luminosity K. The distance to the wound of Astronomers was estimated at about 10 and a half light years.
3. Double star 61 Swan, removed from the ground on a little over 11 light years. Both components of 61 Swan Typical Orange Dwarfs Class K.
4. The Sun-like Star of Tau Whale, removed from the Earth for about 12 light years, with a spectrum of the luminosity G and an interesting planetary system, consisting of a minimum of 5 exoplanets.

Education

The evolution of yellow dwarfs is very interesting. The life expectancy of yellow dwarf is approximately 10 billion years.

As with most stars in their depths, intense thermonuclear reactions flow, in which the hydrogen is mainly burning in helium. After the start of reactions involving helium in the kernel of the star, hydrogen reactions move more and more to the surface. This becomes the starting point in the conversion of yellow dwarf to the red giant. The result of such a transformation can serve as a red giant Aldebaran.

Over time, the star surface will gradually cool, and the external layers will start expanding. At the final stages of evolution, the red giant resets its shell, which forms a planetary nebula, and its core will turn into a white dwarf, which will further compress and cool.

A similar future is waiting for our sun, which is now in the middle stage of its development. About 4 billion years old, it will begin to turn into a red giant, whose photosphere can absorb not only land and Mars, but even Jupiter.

The lifetime of yellow dwarf is an average of 10 billion years. After the whole stock of hydrogen burns, the star increases many times in size and turns into a red giant. The most planetary nebula, and the kernel collaps into a small, dense white dwarf.

White dwarfs

White dwarfs - stars having a greater mass (solar order) and a small radius (radius of the Earth), which is less than the chandaran limit for the selected mass, which is the product of the evolution of red giants. The process of production of thermonuclear energy in them is discontinued, which leads to the special properties of these stars. According to various estimates, in our galaxy their amount ranges from 3 to 10% of the total population.

History opening

In 1844, a German astronomer and mathematician Friedrich Bessel, when superviving Sirius, discovered a small deviation of the star from straight movementand made an assumption about the presence of Sirius an invisible massive satellite star.

His assumption was confirmed already in 1862, when American astronomer and telescopter Alvan Graham Clark, engaged in the adjustment of the largest refractor, discovered near Sirius a non-surge star, which Sirius B. was subsequently

White Dwarf Sirius B has low luminosity, and the gravitational field affects its bright companion is quite noticeable, which indicates that this star has an extremely small radius with a significant mass. So for the first time the type of objects called white dwarfs was opened. The second similar object was the Maanna Star, located in the constellation of fish.

How are white dwarfs are formed?

After in an aging star, all the hydrogen will be uninstalled, its kernel is compressed and heated, it contributes to the expansion of its external layers. The effective star temperature drops, and it turns into a red giant. A rarefied stars shell, very poorly connected with the nucleus, with time dissipated in space, flowing to neighboring planets, and a very compact star, called white dwarf, remains on the place of the Red Giant.

For a long time, it remained a mystery, why white dwarfs having a temperature superior to the temperature of the sun compared to the size of the sun is small, until it turned out that the density of the substance inside them is extremely high (in the range of 10 5 - 10 9 g / cm 3). Standard dependency is a mass-luminosity - for white dwarfs there is no, which distinguishes them from other stars. In an extremely small volume "packaged" a huge amount of substance, which is why white dwarf density is almost 100 times the density of water.

The temperature of the white dwarfs remains almost constant, despite the lack of thermonuclear reactions inside them. What is explained? Due to strong compression, the electronic shells of atoms begin to penetrate each other. It continues until the distance between the nuclei becomes the minimum, equal to the radius of the smallest electronic shell.

As a result of ionization, electrons begin to move freely relative to the nuclei, and the substance inside the white dwarf acquires physical propertieswhich are characteristic of metals. In such a substance, the energy to the surface of the star is transferred by electrons, whose speed is increasingly increasing: some of them move at a speed corresponding to a million degree temperature. The temperature on the surface and inside the white dwarf may differ sharply, which does not lead to a change in the diameter of the star. Here you can make a comparison with the cannon core - cooling, it does not decrease in volume.

White dwarf fuses extremely slowly: for hundreds of millions of years the radiation intensity drops by only 1%. But in the end, it will have to disappear, turning into black dwarf, for which trillions may be required. White dwarfs can be called unique objects of the universe. Playing conditions in the earthly laboratories in which they exist, no one else managed.

X-ray radiation of white dwarfs

The surface temperature of young white dwarfs, isotropic star nuclei after resetting the shells is very high - more than 2 · 10 5 K, however quickly falls due to radiation from the surface. Such very young white dwarfs are observed in the X-ray range (for example, the observations of the White Dwarf Hz 43 Rosat satellite). In the X-ray range, the luminosity of white dwarfs exceeds the luminosity of the stars of the main sequence: the illustrations of the Sirius made by the X-ray telescope "Chandra" can be illustrations - on them White Dwarf Sirius B looks brighter than Sirius and spectral class A1, which in the optical range of ~ 10,000 times Bright Sirius B.

The surface temperature of the hottest white dwarfs - 7 · 10 4 K, the coldest - less than 4 · 10 3 K.

A feature of the radiation of white dwarfs in the X-ray range is the fact that the main source x-ray radiation For them, it is a photosphere, which dramatically distinguishes them from "normal" stars: in the recent in the x-ray eats the crown, warm up to several million Kelvinov, and the temperature of the photosphere is too low for the emission of X-ray radiation.

In the absence of accretion, the source of luminosity of white dwarfs is the supply of thermal energy of ions in their depths, therefore their luminosity depends on age. The quantitative theory of the cooling of white dwarfs was built in the late 1940s Professor Samuel Kaplan.

7. Black Dwarfs

Black dwarfs - The last stage of evolution white Dwarfat which it ceases to emit in the visible range. Currently, black dwarfs refer to the class of white dwarfs, but with the reservation, that this is the final stage of his life. In order to understand what black Dwarf, you need to deal with the concept white Dwarf.

What is White Dwarf and what is his nature?

Take as an example our The sun. During the thermonuclear reaction to the sun, hydrogen turns into helium, the star expands slowly, becoming heavier. Over time, when hydrogen becomes even less, and helium is more, from the latter there will be even more heavy elements, such as carbon, oxygen, iron. The sun will bloom, turning into red Giant. His external layers will be far behind the orbit of the Earth.

When the mass of the shine becomes critical, it will explode supernova, "throwing out" the external layers. At the same time, the masses of our Sun will not be enough to form a black hole or become a neutron star. After the explosion, the sun will be white Karlik.

After throwing part of the mass, the star becomes unable to continue the process of formation of thermonuclear energy. Now white Dwarfslowly cool down, gradually moving into a category black carlikov. At the same time, the star is very stable and will be in this state a very long time.

White dwarfs (and black dwarfs including) They may differ in their composition, luminosity, mass and by other parameters, but in general they are all stars, the mass of which is comparable to the mass of the sun or a little more, and their diameter is ten times less than sunny. The light of such stars is much dimly than before.

Nearest K. Earthwhite dwarf is star Wang Maanenawhich is 14.4 light years in the constellation of fish. And perhaps the most famous white dwarf is a star Sirius B.which is one of the stars star system Sirius. Mass stars Sirius B. Approximately equal to the solar, it makes a star of one of the largest stars among the white dwarfs.

Each of us sometimes looks into the sky, on the myriad of shimmering stars, and set as a question "What hides space?". It is quite natural to dream that is far beyond our reach. Perhaps, in some solar system, located far from us, another type of living beings looks at our sun, which with their prospects is only a small point in the sky, and goes, what secrets are hiding behind her.

Despite all attempts, we will never fully understand everything that hides cosmology, but it does not reduce our desire and effort to know as much as possible. In this list, ten fascinating stars are collected: some of them are already well known, and some scientists only build hypotheses.

10. Hypergigant.

Pretty boring type of stars, compared to the rest of the stars in this list, it was included here only because of its size. It is difficult for us to imagine how really these monsters are enormous, but the radius itself big Star, well-known science today (NML Cygni) 1,650 times more than the radius of our Sun, and is 7.67 astronomical units (1 147,415,68,296 kilometers). For comparison, the orbit of Jupiter is at a distance of 5.23 astronomical units from our Sun, and Saturn's orbit by 9.53 astronomical units. Because of their huge sizes, most of the hypergigants live at best, less than a couple of dozin of millions of years, before turning into supernovae. Bethelgeuse hypergigant (Betelgeuse), which is located in the Constellation of Orion, should turn into a supernova for the next few hundred thousand years. And when he does it, he will shine brighter than the moon, more than a year, and will be visible during the day.

9. Hypercare Star


Unlike all other stars in this list, hypersproorny stars are generally conventional stars that do not have any distinctive or interesting qualities, except that they raise through the space at insane speeds. Hyper-star stars, the speed of which reaches more than 1.5-3 million kilometers per hour, appear as a result of the fact that the stars are approaching too close to the center of the Galaxy - which throws the stars on ultrahigh speeds. All known hyper-speed stars in our galaxy move at a speed exceeding the cosmic more than twice. Consequently, in the end, they will completely fly out of the galaxy and will drift in the dark throughout their lives.

8. Cefeida


Cefheidam or to the pulsating variable stars include stars, the mass of which exceeds the mass of our Sun is 5-20 times. These stars are regularly increasing and decreased in size, which creates the impression of ripples. Cefeida expands due to incredibly strong pressure inside their dense nuclei, but as soon as they expand, the pressure falls, and they appear again. This cycle of extensions and shootings continues throughout their life until the star ceases to exist.

7. Black Dwarf


If the star is too small in order to become neutron or just explode to the supernova, she, in the end, turns into white dwarf - an incredibly tight and dim star, which spent all its fuel and in the core of which no longer goes the division of the atomic nucleus chain reaction. Often, white dwarfs, the size of which does not exceed the size of the earth, slowly cooled through the electromagnetic radiation. After a very long time, white dwarfs finally cease to radiate light and heat - thus becoming, thus, the star that scientists is called black dwarf, and which is almost imperceptible to the observer. The transition to the state of black dwarf means the end of star evolution for many stars. It is believed that at the moment there are no black dwarfs in the universe, because in order for them formed, too much time is required. Our sun degenerates in black dwarf in approximately 14.5 billion years.

6. Shell stars


When people think about the stars, they imagine huge burning spheres floating in space. In fact, because of centrifugal powerMost stars are slightly flattened or flat poles. For most stars, this flattening is quite insignificant in order not to pay any attention to it, but in the stars of some proportions that rotate in the wild speed, this flattening is so strong that gives them a rugby ball form. Because of its high rotational speeds, these stars also discard the huge amounts of matter around their equator, creating a "shell" of gas around them, thus forming a shell star. In the image above, that white, a little transparent mass that surrounds the stars of the star Ahernar (Alpha Eridana) and is a "shell".

5. Neutron Star


As soon as the star becomes supernova, only a neutron star usually remains from her. Neutron stars are very small and very dense balls consisting of (as you have already guessed) neutrons. Many times more denser than the kernel of the atom, and the size of less than a dozen kilometers in diameter, neutron stars really represent a wonderful product of physics.

Due to the extraordinary density of neutron stars, any atom, which comes into contact with their surface, is almost instantly burst into parts. All non-neutron subatomic particles first disintegrate on their regular quarks, and then "reformed" into neutrons. As a result of this process, a huge amount of energy is released, which is so much that as a result of the collision of the neutron star with the medium-sized asteroid, there would be an explosion of gamma-radiation with a much larger amount of energy than our sun would be able to work out for its entire time. Already only for one reason, any neutron star, which is not far from our solar system (At a distance of several hundred light years) is a very real threat to the destruction of the Earth by the emission of deadly radiation.

4. Dark Energy Star


Because of many problems associated with our current understanding of black holes, especially with regard to quantum mechanics, many alternative theories were put forward to explain our observations.

One of these theories is the theory of the star of dark matter. There is a theory that when a huge star is destroyed, it turns into a black hole, but in the space-time, mutating dark matter. Because of quantum mechanics, this star must have a rather unique property: outside of its horizon of events, she must attract all the matter, while inside, outside of its horizon of events, it will braid all the matter. In theory, this is because dark matter has a "negative" force of grave, which repels everything that approaches it, just as the same magnet poles are repelled from each other.

In addition, in accordance with this theory, as soon as the electron passes through the horizon of the events of the dark energy star, it turns into a positron, also known as an antieccratron, and discarded. When this antiparticle faces a normal electron, they are mutually destroyed by forming a small emission of energy. It is believed that this process, on a large scale, is able to explain a huge amount of radiation, which is thrown from the center of the Galaxik - precisely from there, where alternative theories And there are black holes.

For the most part, it is easiest to represent the star of the dark energy in the form of a black hole, which throws away the matter and does not have a singularity.

3. Iron Star


Stars create more heavy elements with the help of nuclear synthesis - a process, during which more light elements merge to form more heavy elements. As a result of this process, energy is released. The harder item, the less energy is released when it is merged. Typical by converting elements for stars is considered the following: hydrogen is converted to helium, then helium into carbon, carbon to oxygen, oxygen in neon, neon in silicon, and then - ultimately - silicon in iron. For iron synthesis, more energy is required than it is released, therefore iron is the last step in any stable reaction of nuclear synthesis. Most stars die before they begin to synthesize carbon, but those of them that reach this stage, or the next behind it, usually shortly after that explode to the supernova.

The iron star, which consists entirely of iron, but, nevertheless, continues the paradoxical emission of energy. But how? Using the tunnel effect. The tunnel effect is a phenomenon in which the particle overcomes the barrier, which under normal conditions it would not be able to overcome. For example: if you throw a ball about the wall, it usually will hit it and bounce. However, according to quantum mechanics, There is a small chance that the ball will fly through the wall and will hit a person standing behind the wall.

This is an example of quantum tunneling. Of course, the likelihood of such a case is infinitely small, but at the atomic level it happens quite often - especially in such huge objects as stars. Usually, in order to synthesize iron, it is necessary a large number of Energy, as there is some barrier to it, preventing synthesis - it means that iron absorbs more energy than it gives. With the tunnel effect of iron can be synthesized without absorbing energy. To facilitate understanding, imagine two small balls rolling towards each other, and in a collision they suddenly become one of the whole. Usually such a merger would require huge energyBut tunneling allows it to produce it without energy at all.

The synthesis of iron through the tunnel effect, the phenomenon is very rare, so the iron star would have to have an incredibly large mass, so that the reaction of nuclear synthesis constantly passed. For this reason, and because the iron is quite rare element in the universe - it is believed that 1 quingenillion years (10 in 1503 degrees) will be held before the appearance of the first iron star.

2. Quasi-Star


"Mensions, Merzayi, Quasi-Star!
Far away, Ile is close?
So different from others
Light blind them.
Merezayi, Mensy, Quasi-Star!
In thoughts, I always with you
Georgy Antonovich Gamov, "Quasar", 1964.

Hypergigants are the largest of the stars, usually turn into black holes, the mass of which is ten times more masses Our sun. Naturally the question arises: where can supermaissive black holes in the center of galaxies, weighing a billion stars? No ordinary star can not be so big to generate such a monster! Of course, you might think that black holes gradually grow up, absorbing matter, but, contrary to widespread opinion, this is a very slow process. Moreover, most supermassive black holes were formed in the first few billion years of life of our universe, which would not give enough time to any ordinary black hole to grow up to those monsters that can be seen now. According to one of the theories, the first stars of the third generation, which were more current hypergigimants and consisting of helium and hydrogen, quickly died and created huge black holes, which subsequently connected to one supermassive black hole. According to another, more likely, theory of supermassive black holes - "Children" quasi-stars. In the first billion years, huge clouds of helium and hydrogen moved in the universe. If the matter is contained in these clouds, quickly clenched - she could produce great star With a small black hole in the center - Quasi-Star, brightness of a billion stars. Usually such a scenario would have led to the formation of a supernovae, after which the "shell" of the star and its surrounding matter would break out into the surrounding space. But, if the cloud of matter, the surrounding star, is quite large and dense, the matter will withstand the explosion and starts to absorb the black hole. "Fallen" a huge volume of matter black hole It would be grown to huge sizes for a short period of time. As an example: imagine that you have a small bomb surrounded by cardboard. If the bomb explode like a supernova, the cardboard will fly away, and the black hole formed as a result of the explosion could not absorb matter. But, if instead of cardboard there will be a thick layer of concrete, the explosion could not move the wall that would subsequently be able to absorb the black hole.

1. Boson Star


In the universe there are two types of particles: bosons and fermions. The easiest difference between them is that fermions are particles with a semi-pervagant spin value, while boson particles have a whole spin value. All elementary and composite particles, such as electrons, neutrons and quarks are fermions, while the bosons include photons and gluons. Unlike fermions, two or more bosons can be in one place.

To facilitate understanding: Fermions are buildings, and bosons are ghosts. In one place there may be one building, as it is impossible to build two buildings in the same place, but thousands of ghosts can be in one place or building, as they are not perfect (bosons actually have a mass, it is just an example ). The number of bosons in one place is unlimited. All known stars consist of fermions, but if there are stable bosons with some mass, then bosomic stars can also be hypothetically.

Given that gravity depends on the mass, imagine that it may happen if there is a type of particle that at one point of the space can coexist the infinite number of particles of this type. Returning to our example - imagine that every ghost has some kind of, even a small mass, and now put billions of ghosts in one point - it will turn out a point with a huge mass that will attract other objects with its huge gravitational force. Thus, boson stars may have an endless mass concentrated in an infinite small point of space. According to theories, boson stars, if they exist, are located in the centers of galaxies.