V. Surdin: Planets of other stars
In "astronomical calendars" you can often see phrases like " The sun will move into the constellation Taurus", "Mercury in superior conjunction with the Sun", etc. It would seem that there is no practical meaning in them, because next to the Sun you cannot see anything in the sky.
In this photo, you can easily recognize the Pleiades, a small scoop-shaped open cluster of stars that usually graces the winter night sky. But what are these rays diverging from below? Light from a street lamp? No, these rays are part of the solar corona, and the Sun itself is very close, behind the bottom edge of the image.
To see stars near the Sun, you need to create an artificial eclipse. No, you don’t need to block the Sun with a coin. Such an eclipse has already been created and has been going on for almost 20 years. It takes place on board the SOHO space observatory. The observatory is a joint project between NASA and ESA, and was launched on an Atlas II-AS rocket from Cape Canaveral on December 2, 1995.
None of them large number various models of the origin and development of the solar system have not been promoted to the rank of generally accepted theory.
According to Kant–Laplace hypothesis the system of planets around the Sun was formed as a result of the forces of attraction and repulsion between particles of scattered matter located in rotational movement around the Sun.
For the first time, an English physicist and astrophysicist J. H. Jeans(1877 - 1946) suggested that the Sun once collided with another star, as a result of which a stream of gas was torn out of it, which, condensing, turned into planets. Given the enormous distance between the stars, such a collision seems incredible.
Of the modern hypotheses of the origin of the Solar system, the most famous is the electromagnetic hypothesis of the Swedish astrophysicist H. Alfvena (1908 - 1995)and English F. Hoyle (1915 - 2001). According to this theory, the original gas cloud from which the Sun and planets were formed consisted of ionized gas subject to the influence of electromagnetic forces. After the Sun was formed from a huge gas cloud through concentration, small parts of this cloud remained at a very large distance from it. The gravitational force began to attract the remaining gas to the resulting star - the Sun, but its magnetic field stopped the moving gas at various distances - exactly where the planets are located. Gravitational and magnetic forces influenced the concentration and thickening of this gas. As a result, planets were formed. When did the most major planets, the same process was repeated on a smaller scale, thus creating satellite systems.
The hypothesis of the formation of the Solar system from a cold gas and dust cloud surrounding the Sun, proposed by a Soviet scientist, is also known O.Yu. Schmidt (1891 - 1956).
According to the currently generally accepted hypothesis, the formation of the Solar System began about 4.6 billion years ago with the gravitational collapse of a small part of a giant interstellar gas and dust cloud. This initial cloud was probably several light years in size and was the progenitor of several stars.
During the process of gravitational compression, the size of the gas and dust cloud decreased and, due to the law of conservation of angular momentum, the speed of rotation of the cloud increased. The center, where most of the mass had gathered, became hotter and hotter than the surrounding disk. Due to the rotation, the compression rates of the clouds parallel and perpendicular to the rotation axis differed, which led to the flattening of the cloud and the formation of a characteristic protoplanetary disk with a diameter of approximately 200 AU. and a hot, dense protostar at the center. It is believed that at this point in its evolution the Sun was a T Tauri star. Study of such stars shows that they are often accompanied by protoplanetary disks with masses of 0.001 - 0.1 solar masses, with the overwhelming percentage of the nebula's mass concentrated directly in the star. The planets were formed by accretion from this disk (Fig. 27).
Over the course of 50 million years, the pressure and density of hydrogen at the center of the protostar became high enough for thermonuclear reactions to begin. Temperature, reaction rate, pressure and density increased until hydrostatic equilibrium was reached, with thermal energy opposing the force of gravitational compression. At this stage, the Sun became a full-fledged star main sequence.
Fig. 27 Evolution of the Sun
The solar system will exist until the Sun begins to evolve outside the main sequence of the Hertzsprung–Russell diagram, which shows the relationship between the brightness of stars and their surface temperature. Hotter stars are more luminous.
The Sun burns its reserves of hydrogen fuel, and the released energy tends to run out, causing the Sun to shrink. This increases the pressure in its depths and heats the core, thus accelerating the combustion of fuel. As a result, the Sun becomes brighter by about ten percent every 1.1 billion years.
In about 5 to 6 billion years, the hydrogen in the Sun's core will be completely converted to helium, ending the main sequence phase. At this time, the outer layers of the Sun will expand approximately 260 times - the Sun will become a red giant. Due to the extremely increased surface area, it will be much cooler than when on the main sequence (2600 K).
Ultimately, the outer layers of the Sun will be thrown out into the surrounding space by a powerful explosion, forming a planetary nebula, in the center of which only a small stellar core– a white dwarf, an unusually dense object with half the original mass of the Sun, but the size of the Earth. This nebula will return some of the material that formed the Sun into the interstellar medium.
Theories of the origin of the solar system are hypothetical in nature, and the question of their reliability cannot be clearly resolved. modern stage development of science is impossible. All existing theories have contradictions and unclear areas.
The lack of a generally accepted version of the origin of the planetary system has its own explanation. First of all, the uniqueness of the object of observation excludes the use comparative analysis and forces us to solve the difficult task of reconstructing history based only on knowledge about the current state of the Solar system. For example, ideas about the evolution of stars from their birth to death were obtained through the accumulation and statistical processing of observed data on current state many stars different classes located on different stages development. It is not surprising that astronomy knows much more about the development of stars far from us than about the origin and development of our habitat - the Solar System.
Thus, the solar system is a very complex natural formation, combining the diversity of its constituent elements with the highest stability of the system as a whole. At a huge number and the diversity of the elements that make up the system, with the complex relationships that are established between them, the task of determining the mechanism of its formation turns out to be very difficult.
The Solar System includes:
· Sun;
· 4 planets terrestrial group: Mercury, Venus, Earth, Mars and their satellites;
· the belt of minor planets - asteroids, which includes the dwarf planet Ceres;
· countless number of meteorite bodies, moving both in swarms and singly.
· 4 giant planets: Jupiter, Saturn, Uranus, Neptune and their satellites;
· hundreds of comets;
· centaurs;
· trans-Neptunian objects: the Kuiper belt, which includes 4 dwarf planets: Pluto, Haumea, Makemake, Eris and the scattered disk;
· Remote areas that include the Oort and Sedna clouds;
· Border areas.
Sun
The Sun belongs to the ordinary stars of our Galaxy and is a hot gas (plasma) ball of predominantly helium-hydrogen composition, which is diluted with an admixture (about 1%) of other chemical elements, the ratio of which varies from the surface to the core. The upper layers of the Sun contain about 90% hydrogen and 10% helium. The core contains only 37% hydrogen. The ratio between hydrogen and helium changes over time in favor of helium, since thermonuclear reactions have been occurring on the Sun for 4.5 billion years, transforming hydrogen nuclei into helium nuclei. Every second, about 600 million tons of hydrogen are converted into helium at a temperature of about 15 million 0 C. At the same time, 4.3 million tons are converted into radiant energy (Fig. 28).
We all quite often hear that scientists have discovered something or someone on such and such a star or on some planet, or simply conducted research, and... so on. But few people think about why planets are called planets, and stars are called stars, and what kind of properties they have. important differences, since some were separated from others? At the same time, almost each of us at least once in our lives asked a rather stupid question: “Is the sun a star or a planet?” Also, almost every person will immediately answer this question that the Sun is, of course, a star, but not everyone is able to explain why it is a star and not a planet.
A completely logical question arises: what is the difference between a star and a planet?
The difference between them is simply huge, although at first glance it is not very noticeable
1. The first and most important thing is that stars are capable of independently emitting light and heat, unlike planets, which are only capable of reflecting the rays of light that fall on them from other luminaries, being essentially dark bodies.
2. Stars have much more high temperatures surfaces than any known on at the moment planets. The average temperatures of their surfaces range from 2,000 to 40,000 degrees, not to mention the layers located closer to the center of the cosmic body, where temperatures may even reach millions of degrees.
Data from SDO, a solar spacecraft, over three years of operation
3. Stars significantly exceed even the largest planets in mass.
4. All planets move in orbits relative to their luminaries, which, in turn, at the same moment remain completely motionless. This happens in a similar way to how our Earth revolves around the Sun. Thanks to this, it is possible to observe the planets different phases just like the Moon.
5. All planets, in their chemical composition, are formed from both solid and light particles, in contrast to stars, which predominantly consist of only light elements.
6. Planets often have one or several satellites, but stars never have such “neighbors”. But at the same time, the absence of a satellite is, of course, not a fact that this cosmic body is not a planet.
7. On the surfaces of absolutely all stars, nuclear or thermonuclear reactions necessarily occur, accompanied by explosions. In turn, these reactions are not observed on the surfaces of planets, well, unless in exceptional cases, and then only on nuclear planets and only very, very weak nuclear reactions.
We can definitely say...
Now we can absolutely say that the Sun is a typical star (the so-called G-type yellow dwarf). Because 8 planets revolve around it, forming the Solar System with it; it independently emits light and heat - the average surface temperature is 5000-6000 K; consists predominantly of light elements such as hydrogen and helium - almost 99%, and only 1% are solids; thermonuclear reactions constantly occur on its surface; and in its size it is several times larger than any planet in the solar system.
Well visible on a clear night.
Planets
Among the countless stars can be easily distinguished by their bright brilliance planets, which is translated from ancient Greek - wandering stars. These celestial bodies were so named by the ancient Greeks because from day to day they moved relative to seemingly motionless stars and appeared as bright luminaries in the night sky.
Planets of the Universe
As you know, planets are not at all: they receive light from and move around it in orbits that are close in shape to a circle.
Comets
In very elongated orbits, after one or another period of time, distant guests of our planet fly from interplanetary spaces. solar system - comets, or tailed stars(translated from Greek). The sudden appearance of a comet has always frightened the ignorant person.
They said that devastating bloody wars would begin, unrest, famine, pestilence would occur everywhere, and even the end of the world would come.
It can be observed much more often, especially at the end of summer, August star shower. In the old days it was believed that every person has his own star in the sky, and when he dies, his star also fades and falls.
Stars, of course, don't fall. These are fragments of celestial bodies and disintegrated comets: they heat up to several thousand degrees and begin to glow when they enter the earth’s atmosphere.
Meteorites
The hot air around the falling bodies also glows. In the event that they do not burn out completely, turning into hot gas, they fall to the ground sky stones, as they used to be called, or meteorites. Sometimes they reach enormous sizes.
The meteorite, which fell in February 1947 in the area of the Sikhote-Alin ridge with a shower of fragments, is believed to weigh up to one hundred tons. At the site of his fall, I discovered many deep craters up to 30 meters in diameter. Over two years, about 23 tons of meteorite fragments were collected in this area.
The famous Tunguska meteorite, which fell in the summer of 1908 in the remote taiga, near the small village of Vinovara near the river. Podkamennaya Tunguska (Krasnoyarsk Territory), has not yet been discovered, despite many years of searching. Scientists believe that it exploded during the fall and completely disintegrated into tiny particles metal dust.
It was actually discovered when analyzing the soil in the area of the explosion, which was heard 1000 kilometers away. The explosion column rose to a height of at least 20 kilometers and was visible 750 kilometers in circumference. Over a huge area - up to 60 kilometers in diameter - trees were felled, with their tops in all directions from the explosion site.
Scientists believe that about 10 tons of meteorite material falls on Earth per day.
Usually, among the dimly flickering stars, brighter ones can be distinguished - bluish-white, yellow, reddish. Most stars are in the wide silver stripe - Milky Way, which, like a giant hoop, encircles the vault of heaven.
With his penetrating gaze, man penetrated into the hidden depths of the universe and finally saw, through powerful telescopes, distant worlds like Milky Way. It is not difficult to conclude from this what a modest place ours occupies in the universe - infinite in time and space, having neither beginning nor end.
A star is a red-hot self-luminous ball
According to strict astronomical accounting - millions. The stars and planets of the Universe, as they say, are counted individually, included in special lists, in a catalog, and marked on special maps.
Each star - a red-hot self-luminous ball similar to our Sun.
Star Sun The stars are very far from us. To the nearest star - that's what it's called Proxima, that is, in Latin, the closest one, - it would have taken a very, very long time to get there even with the help of a rocket. The light from this star to the Earth takes four years, as determined by astronomers.
The speed of light is very high - 300,000 kilometers per second! From this we can draw the following conclusion: if, say, Proxima goes dark today, people will observe its last ray in the sky for four whole years.
One hundred and fifty million kilometers separating from , light travels in 8 minutes 18 seconds. How close the Sun is to us compared to its closest neighbor!
The size of the stars varies greatly. The giant star (from the constellation Cepheus) is 2300 times larger than the Sun, and the small stars (Kuiper star) are almost half the size of the Earth.
Star temperature
Various and star temperature. Bluish-white stars are the hottest: their surface temperature is 30,000°; on yellow stars it is already cooler - 6000°, and on red stars 3000° and lower. Our Sun is a rather weak star, yellow dwarf, as astronomers call it.
The Birth of Stars
By studying the celestial bodies, scientists have made many interesting conclusions about birth of stars, about their development and chemical composition. Chemical composition celestial bodies are studied with a special device - a spectroscope. It allows you to detect even negligible amounts of a substance using the characteristic color lines of the spectrum.
Spectrum
Spectrum(from the Latin “spectrum”) - visible, vision.
You can get an idea of the spectrum from a rainbow after rain. It attracts with subtle transitions from one color to another: from red - through orange, yellow, green, blue and indigo - to violet.
You will never forget the place of each color in the spectrum if you remember this little fable:
Every hunter wants to know where the pheasant is sitting.
Here initial words denote color.
When a ray of light, passing through a triangular glass prism, falls on a sheet of paper or a white wall, a beautiful rainbow stripe is also obtained. The same colored stripe you will see it on the ceiling or wall if a ray of sun falls on the edge of a mirror or the light sparkles with colored tints on the faceted balls and pendants of a theater chandelier.
Hot solids and liquid bodies, as well as gases under high pressure form continuous spectra in the form of rainbow stripes, while rarefied gases, when heated, give not a continuous, but a linear spectrum; it consists of individual colored lines characteristic of each substance, separated by dark spaces.
The adaptation of the spectroscope to the telescope made it possible to obtain photographs of the spectra of very distant celestial bodies and from here draw the conclusion that not a single one has yet been detected on them chemical element, unknown on Earth. The same results were given by chemical analysis meteorites. Spectral analysis of distant stellar worlds and chemical analysis of meteorites convincingly indicate unity of matter of the Universe.
Astronomers using the Spitzer telescope discovered dust particles containing elements of cometary material in the vicinity of the white dwarf G29-38, which allowed them to assume the possibility of the existence of comets and planets in the outer orbits of dead stars.
According to existing theory, white dwarfs are formed from stars similar to our Sun: at one stage of their evolution, the stars become red giants, and then over millions of years, as a result of powerful explosions, they turn into white dwarfs. If the star G29–38 previously had planets, then the formation of a red giant should have absorbed them. But planets and comets rotating in outer orbits could survive the death of a star.
This hypothesis is confirmed for the first time by astronomers' discovery of a dust disk orbiting the star G29–38, which became a white dwarf about 500 million years ago. According to scientists, the dust formed much later than the explosion of the star. This discovery is the first evidence that comets and planets can live longer than the stars, around which they revolved. Observations with the Spitzer telescope will allow us to make assumptions about the evolution of systems similar to our Solar System.
“Perhaps dust around the white dwarf G29–38, detected using space telescope Spitzer was formed relatively recently. These could be the remains of a comet that made its way from the outer orbit and disintegrated under the influence of the gravitational forces of the star,” comments Dr. William Reach from Science Center Spitzer of the California Institute of Technology in Pasadena.
The reason for exploring the surroundings of the dead star was the discovery of a strange source by other observatories. infrared radiation near G29–38. Spitzer's powerful infrared spectrometer made it possible not only to see this source - a dust disk - in detail, but also to identify it molecular structure, which turned out to be similar to the structure of comets in the Solar System, reports SpaceFlightNow.
"We discovered large number contaminated silicate particles whose size suggests they came from a comet rather than some other space object,” says astronomer Marc Kuchner of NASA's Goddard Space Flight Center in Greenbelt, Maryland. In our solar system, comets “live” in cold border regions called the Kuiper belt and the Oort cloud. It is only if something distorts their orbits, such as other comets or outer planets, that they begin to make periodic trips to the Sun. For many comets, this voyage ends in death - they are either slowly destroyed by flying too close to the Sun, or collide with planets, such as Comet Schumacher-Levy 9, which fell on Jupiter in July 1994.
Although the most likely source of the dust around G29–38 is a comet, there are other hypotheses. According to one of them, this may be a new protoplanetary disk emerging around a white dwarf.
