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Sun

The position of the Sun among the stars. Nearest stars.

© He talks about the stars closest to us:
Dr David Whitehouse is an astronomer and science commentator for the BBC World News Service.

Closest neighbors.

In order to determine the deserved place of our Sun among the stars, let's first look at its neighbors. The Sun's closest neighbor is a system of three stars orbiting one another. The brightest of them Alpha Centauri A, - this is very similar to our yellow Sun. Alpha Centauri B slightly smaller, and its light has an orange tint, as its surface temperature is cooler - about 4800 °C, while the temperature of the Sun reaches 5800 °C. tells us about its temperature. Cool stars are red, hotter ones are orange, yellow and bluish-white.

The orbital period of the two main stars of the Alpha Centauri system relative to each other is about 80 years. They are located quite far from each other (the distance between them is comparable to the distance from the Earth to the Sun or from the Sun to the planet Uranus). The third star in the system Alpha Centauri - C, or Proxima Centauri, got its name due to the fact that it is located closest to Earth. It is a much more typical representative of the stellar community, despite the fact that this star is dim, red (and therefore cold) and small. It is located far from the main pair, about 300 times greater than the distance from the Sun to Pluto. If our Sun had a companion star like Alpha Centauri C, it would look like an ordinary star in the night sky. It could be observed with the naked eye, but it would not stand out against the background of other stars, moreover, it would seem dimmer.

Barnard's Star

Our cosmic neighbor is also Barnard's star, named after Edward Emerson Barnard, who lived about a century ago and is said to have been one of the keenest astronomers on earth. This modest little star is located towards the constellation Ophiuchus. It is the closest star that can be studied from the northern hemisphere using telescopes, but only a few astronomers are currently making such observations. Barnard's Star very reminiscent Proxima Centauri and according to the classification is a red dwarf, the most common type of star in the galaxy.

The mass of red dwarfs is about 10-30% of the mass of our Sun. Their own nuclear reactions proceed slowly, so their lifespan is 10 billion years. These stars are very interesting, and studying them helps to better understand our Sun. The outer layer of our Sun is a zone of convective energy transfer, and in red dwarfs these zones are more powerful and located deeper. In fact, some of these stars may be entirely convective. This leads to the generation of strong magnetic fields. When these fields rise above the red surface of stars, huge explosions can occur.

Stellar flares from dwarf stars are much more energetic than those that can be observed on our Sun. These stars were discovered because they flared brightly for several minutes. No wonder they got the name "flaring stars". In addition, these giant stellar flares were discovered to generate radio waves. They were first recorded by Manchester University professor Bernand Lovell in 1959, and later a new large telescope installed at the Jodrell Bank Observatory was used for this purpose. Many years ago, a young graduate student (namely myself) ( Let me remind you that this conversation is being conducted by David Whitehouse, approx. VC.) spent many sleepless nights studying the controls of this radio telescope in order to use new techniques to detect starbursts of red dwarfs in nearby space. Materials related to this work are kept in the library at Jodrell Bank.

One of the stars we studied did not want to reveal its secrets. During one year of observation there were many outbreaks, and the next year they were practically absent. I remember writing in my notebook, “Is the activity of this star similar to the 11-year cycle of the Sun?” May be.

Barnard's Star moves through space, and its apparent movement across the sky is the fastest of all. However, since this star is too small, its movement does not affect the shape of the constellations. The constellations seem unchanging, and, from the point of view of man and the duration of his life, they are so. However, over the course of centuries, stars slowly change their position in space. For example, the period of revolution of our Sun and planets solar system around the center of the galaxy is 200 million years. The process occurs so slowly that constellations that are 10 thousand years old are quite recognizable. However, if a modern astronomer were somehow transported back in time a million years, then, looking at the starry sky, he would be confused. Barnard's Star moves across the sky at a speed of half a degree every 175 years. It is approaching and approximately in 11800 it will be close to Earth, at a distance of only four light years (closer than Proxima Centauri).

Many years ago, some astronomers believed that a planet was orbiting Barnard's Star. Observations showed that, as it moved across the sky, the star swayed slightly relative to its vertical axis. It is possible that this wobble was caused by the gravity of one or more large planets located nearby. However, no clear confirmation could be found, and the oscillation of the star itself was almost imperceptible. Over the past 10 years, the discovery has been made that there are many planets in the neighborhood of the solar system, revolving in orbits around their stars, i.e. is full of planets, and there is nothing unusual about it.

Other nearby stars

There is another red dwarf near the solar system, which became famous thanks to the television series “Star Trek”. This Star Wolf 359, which featured a spectacular battle between the United Federation of Planets and the Borg - a high-tech pseudo-race of cyborgs controlled by a single brain and increasing their numbers by assimilating entire worlds. Wolf 359 located in the constellation Leo and is the dimmest among its neighbors and one of the dimmest stars known to mankind. If the Sun were replaced by the star Wolf 359, there would either be no daylight, or it would be light that was only 10 times brighter than moonlight.

There are many more red dwarfs not far from Earth. Among them are Lalande 21 185 in the constellation Ursa Major. It is necessary to remember and UV China- a pair of red dwarfs and the prototype of the entire class of flare stars, which includes Proxima Centauri and Wolf 359. The distance between the stars of the pair UV China 6 times the distance from the Earth to the Sun, and the period of their revolution relative to each other is 25 years. Their total mass is only 30% of the mass of the Sun.

The brightest star near the Sun is Sirius, which is also called the Dog Star because it is located in the constellation Canis Major . In 1862 it was discovered that Sirius is a double star. Sirius A- a bluish-white star, it is 2 times larger than our Sun. Its surface temperature is 10,000 °C. Her little companion Sirius B the closest example of a white dwarf star to Earth. This is an extremely dense star that has completed its evolution and has shrunk to the size of a small planet. It is the same size as our Earth, but has the mass of the Sun. Its substance is so dense that a cup filled with it would weigh as much as a jetliner. Standing on its surface, you would weigh 100 times more than standing on Earth. These two completely different stars rotate relative to each other with a period of 50 years, and the average distance between them is 20 times greater. The last of the stars known to us, the distance to which from Earth is less than 10 light years, was named Ross 154 and is, again, a red dwarf.

Where are we flying?

In 1783, William Herschel published his observations, which served as the impetus for the discovery solar movement. He determined that our solar system is moving between neighboring stars in the direction of the star Lambda of Hercules, or Maasim, which means “wrist” in Arabic. To denote this direction, Herschel introduced the term apex (from the Latin “arech” - top), which came to mean a point on celestial sphere, in the direction in which the astronomical object is moving. The brightest star in the sky, Sirius, is the antiapex, i.e. the point in the direction from which the Sun moves.

This is the direction in which the Sun moves in its orbit around the center of the Milky Way. All 100 thousand stars of our Galaxy revolve around its center. The closer a star is to the center of the Galaxy, the faster it moves. As for our Sun, it is 24 thousand light years away from the center and moves in orbit at a speed of 220 km/s, making full turn for 230 million years. It turns out that during its existence the Sun circled the Galaxy about 18 times (according to other sources, 25-30 times). In addition to its circular motion around the center, the Sun also makes oscillatory movements up and down relative to the plane of the Galaxy. The oscillation period is 70 million years. This means that we pass through the median plane of the Galaxy every 35 million years. Some scientists compare this period with the interval between mass extinctions of living beings on Earth. It is no secret that the number of cosmic rays reaching the Earth has been increasing over the past 100 thousand years as the Earth approaches the median plane of the Galaxy. Perhaps this fact will affect cloudiness and, consequently, the Earth's climate.

Consists of a series of spiral branches, and our Sun is in this moment is in a small spiral arm called Orion, which connects the larger Sagittarius and Perseus spiral arms. The Earth passes through the main spiral arm every 100 million years, and the passage takes 10 million years. In the process of passing through the spiral arm, the influence of the nearest supernova, and its intense radiation, emitted even at a distance of tens of light years, can change the Earth's climate.

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Since ancient times, man has directed his gaze to the sky, in which he observed thousands of stars. They fascinated him and made him think about the world around him and space. Over the centuries, knowledge has accumulated and been systematized. When did it become obvious that stars are not just luminous points, but real ones? space objects, and of enormous magnitude, our ancestors had a dream - to fly to them. But first it was necessary to determine how far they were.

Here is the significant difference between them:

1. Size. A star, as a rule, is much larger than ordinary planets.
2. Weight. The star has a much greater mass than the planet.
3. Chemical composition. The first contains predominantly light elements, the second - both light and heavy.
4. Temperature. For planets it is much lower. This explains the difference in the radiation spectra: planetary radiation is mainly infrared, stellar radiation is mainly ultraviolet, x-ray and gamma radiation.
5. Brightness and luminosity intensity. The stars themselves emit light, and the planets only reflect it.
6. Chemical reactions. In stellar bodies thermonuclear and nuclear reactions occur, and throughout the entire volume of their body, on planetary bodies only nuclear reactions are possible, and only in the center of the nucleus.
7. Movement in space. Planetary bodies move around stars along an ellipsis trajectory and may have satellites. Stellar ones do not rotate and do not have satellites.
8. The sun is a star. Moreover, it belongs to the class of yellow stars. The temperature of the Sun is average for her type - not too high and not too low.

Closest star to Earth

If we are talking about the limits of the solar system, then this, of course, is the Sun. It is a star and is closest to us than anyone else. It is also the center of our system. Without it, life on our planet would have been impossible, and the Earth arose along with this star. Even for this reason, it is worth especially close attention.

Like any stars, the Sun is mainly composed of helium and hydrogen. Moreover, the latter cyclically turns into the first. As a result of thermonuclear reactions, heavier elements are formed. And the older the star, the more of these elements accumulate. Our Sun is no longer young in age, it is approximately 5 billion years old. The weight of the star closest to us reaches 5958000000000000000000 Earth tons (for convenience, it is written in other units, but this number is obviously the most obvious).

The diameter of the Sun is 1,392,000 kilometers. Surface temperatures can reach 1,500,000 degrees Celsius. It increases in the center. The atmosphere includes three parts:

• crown;
• chromosphere;
• photosphere.

If we talk about the nearest star outside our system, then it is the small Proxima Centauri.

The brightest stars beyond the solar system

Proxima Centauri

She is part of the triple system, which is located at a distance of about four light years from us. Scientifically, a light year is called a parsec. The very name of this asterisk translated from Latin sounds like “nearest.” Which definitely leads to the understanding that the ancients noticed both its features and the nature of its location, giving it a telling name.

Despite the fact that four parsecs seems like an insignificant distance within the Universe, for people it is very far away. And to reach the limits of Proxima Centauri, it will take more than one generation of people.

Even the keenest eye cannot see it among the stars. It can only be found in the sky through a telescope. It shines weaker than the Sun, approximately 150 times. It is also noticeably smaller in size, and the temperature on its surface is two times lower. Astronomers identify this star as a brown dwarf and believe that finding planets near it is unlikely. Therefore, there is no point in flying there.

Alpha Centauri

At the same time, the triple system of Alpha Centauri, also relatively close to us, deserves attention - such objects are not very common in the Universe. They are attractive because the stars in them revolve around one another in intricate orbits, and sometimes it even happens that they “eat” their neighbor.

You will learn about the distances to stars from this video.

Deep space

The most distant object discovered to date in the Universe (of those noticeable without the use of special optical instruments) is the Andromeda Nebula. Its brightness corresponds to approximately a quarter magnitude. And the most distant star to Earth in this galaxy is located from us, according to astronomers, at a distance of 2 million light years. An unimaginable amount! After all, we observe it as it was 2 million years ago - that’s how easy it is to look into the cosmic past!

The closest galaxy to us is a dwarf galaxy, which can be tracked in the constellation Sagittarius. It is so close to us that the Milky Way literally absorbs it. Although it should be noted that in any case it will take 80,000 light years to fly to it. The Magellanic Cloud is not worth mentioning: it lags behind us by almost 170 parsecs.

According to NASA, another 45 stars are located 17 parsecs away from the Sun. In our galaxy as a whole there is over 200 billion stars. Moreover, some of them are so dim that they are almost impossible to detect without the use of special equipment. Probably thanks to latest technologies Scientists will be able to find stars that are even closer to us.

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Interesting information You will learn about the Sun from this video.

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> > > The closest star to Earth

The closest star to Earth- Sun. Explore a star beyond the solar system - bright Alpha Centauri and the 20 closest stars to Earth, with distances.

To catch your friends, you can ask them about the star closest to Earth. Most people immediately start talking about Betelgeuse or Sirius. But here lies the catch. Of course, the Sun is closest to the Earth (150 million km). But what heavenly body, in addition to the Sun, is closest star to Earth?

Which star is closest to Earth?

Alpha Centauri is considered the closest star to Earth besides the Sun. It ranks third in brightness and lives only 4.37 light years away. But this is not a single object, but a triple system. First of all, we see a binary pair orbiting a common center of gravity every 80 years. Alpha Centauri A is brighter than the Sun, while Alpha Centauri B is slightly less bright. The third member of this system is Proxima Centauri. Remember this name, since it is the closest star to Earth (4.24 light years).

The Alpha Centauri system is located in the constellation Centaurus, which can only be seen from the southern hemisphere. But even there you won’t be able to see this star. The fact is that it is too weak and you will need a fairly powerful telescope. To give you an idea, it would have taken New Horizons 78,000 years to get to Proxima Centauri.

Proxima Centauri has been the closest star to Earth for 32,000 years and will remain in this position for another 33,000 years. In 26,700 years it will reduce the distance to 3.11 light years. After it, the closest star to Earth is Ross 248.

The closest star to Earth in the Northern Hemisphere

The closest star to Earth in the northern hemisphere is Barnard's Star, a red dwarf in the constellation Ophiuchus. But it is also dim and not visible to the naked eye. If we take only the stars that can be observed without the use of special equipment, then Sirius is the closest (8.6 light years). It is twice the size and mass of the Sun.

How are distances to stars measured?

Parallax is used to determine the distance to a star from Earth. What's the point? Extend your arm and place your finger in front of a distant object. Close your eyes one at a time and you will understand that the object seems to be moving. This is parallax.

It is necessary to calculate the distance to the star when our planet is in one of the orbits (in summer), and then wait 6 months until it is on the opposite side and measure again. Then we measure the angle in relation to another object. This scheme works for any object living within 100 light years.

There are 45 stars located at a distance of 17 light years from the system. There may be 200 billion in total in the galaxy. Some are so weak that they cannot be detected.

List of 20 stars closest to Earth

This list shows the nearest stars and star systems, as well as the distance from Earth in light years. Some of them have several stars, but are part a certain system. So:

1. Alpha Centauri – 4.2;
2. Bernard's Star - 5.9;
3. Wolf 359 – 7.8;
4. Lalande 21185 – 8.3;
5. Sirius - 8.6;
6. Leithen 726-8 – 8.7;
7. Ross 154 – 9.7;
8. Ross 248 – 10.3;
9. Epsilon Eridani – 10.5;
10. Lecaille 9352 – 10.7;
11. Ross 128 – 10.9;
12. EZ Aquarius – 11.3;
13. Procyon – 11.4;
14. 61 Cygnus – 11.4;
15. Struve 2398 – 11.5;
16. Groombridge 34 – 11.6;
17. Indian Epsilon – 11.8;
18. Dx Cancer – 11.8;
19. Tau Ceti – 11.9;
20. GJ 106 – 11.9.

According to NASA, there are another 45 stars that are within 17 light years of the Sun. Some are so small and dim that they are almost impossible to detect. Who knows, but maybe with improvements in technological capabilities, scientists will be able to find even closer star systems.

Heavenly bodies, which include stars, are some of the most unique creations on the planet. Thousands of astronomers have been studying them for hundreds of years, but they never tire of making new discoveries.

Admiring the starry sky in clear weather, you can notice both bright and dim stars. It seems that the stars closest to Earth should be brighter and more noticeable, but most often the opposite happens - the radiance of distant stars overshadows the light of nearby ones and they become less noticeable. The existence of some stars closest to our planet became known not so long ago, when more powerful equipment began to be used to see them.

"Neighbors" in the Galaxy

The closest star to Earth and at the same time the most famous and contemplated in practice all year round– this is, of course, the Sun. It is far from the largest, but life on the planet depends on it. Much has been written about its size and power. scientific articles, so people in general have a general idea of ​​what it is. But the Sun has many “neighbors” that are located not far from the Earth. Almost all of them have now been thoroughly studied by astronauts. The exception is very small and dim stars.

So, the list of nearby stars:

1. Centauri. This star consists of three parts. All of them are within a radius of 5 light years from the Sun. The first of them is Proxima Centauri, the second is Alpha Centauri A, and the third is Alpha Centauri B. According to recent studies, their age is about 4,850,000 years. The temperature on them is from 3,000 to 5,700 degrees Kelvin;
2. Barnard. It is also known as Barnard's Flying Star. It is a red dwarf and, unlike other stars, moves quickly and approaches the Sun. According to the forecast, in 10 thousand years it will become the closest star to it, but over time it will move away again;
3. Wolf 359. Also a red dwarf, with an apparent magnitude of 13.45;
4. Lalande 21185. It is more than 8 light years away from the Sun. It is a red dwarf with an apparent magnitude of 7.49 and a luminosity of 0.0052;
5. Sirius. Just like Centauri, it consists of several parts, or rather two: Sirius A and Sirius B. The Dog Star (Sirius A) is the brightest star, if you do not take into account the Sun. Its luminosity exceeds, according to various sources, from 17 to 23 solar levels. Sirius B or Puppy is her satellite, a white dwarf.

This is just the top 5 stars that are close to Earth. They are followed in turn by the star Leithen or Ceti (consists of two parts: A and B), Ross 154, Ross 248, Epsilon Eridani and Luthien 786-6. Each star has its own characteristics (weight, luminosity, temperature, size). But, nevertheless, they all belong to the “closest star to Earth” category. This means they are of particular interest not only for astronauts, but also for those who admire the night luminaries.

rice. The nearest bright star is Alpha Centauri

The stars closest to the Sun include a number of bright luminaries that have proper names, as well as several southern stars that are inaccessible for observation at northern latitudes. Their colors are very different: blue (Rigel and Spica), yellow (Capella), orange (Arcturus), red (Betelgeuse and Antares).

Most similar in spectrum and luminosity to the Sun is our closest neighbor - Alpha Centauri, the brightest component. It is only 1.33 ps away from us. Apparently, the most distant star in the immediate environment of the Solar System is Deneb, located at a distance of approximately 450 pc. Distances to Rigel, Betelgeuse and β Southern Cross are also difficult to measure. If we consider the volume of space that needs to be explored before we reach a star like Deneb, we see that it is about (450/1.33), or 40,000,000 times the volume that we would have to explore to discover the star α Centauri.

rice. Rigel (β Orionis)

The M-class star Betelgeuse is also very bright, but it is closer to the Sun than Rigel. Because its surface is relatively cold, the star must be enormous in size to emit so much light. Betelgeuse and Antares are among the very few stars whose diameters can be measured using an instrument called an interferometer. It was found that the diameter of Betelgeuse is about 600 times the diameter of the Sun, and the diameter of Antares is only slightly smaller than the diameter of Betelgeuse. The diameter of the star is so large that the entire orbit of Mars fits inside it, and the star can rightfully be called a giant! Betelgeuse appears and apparently also changes size with an irregular period.

The closest neighbors of the Sun are stars, the distance to which does not exceed 5 pc. The four brightest stars on this list are Sirius, Altair, Procyon and α Centauri. These stars shine brightly in the sky because they are close to us, not because they are exceptionally luminous. These are mostly dwarf stars, or, as we prefer to call them, “main sequence” stars. Many M dwarfs are flare stars. Although their luminosity is usually very low, they can sometimes be a short time become brighter by 2 or more; outbreaks of some of them were repeated many times. At least five stars closest to the sun are flaring. Bright lines are observed in their spectra; this feature is indicated by the letter "e" placed after the spectral class.

rice. Comparative sizes of the nearest ones bright stars

It should be noted that the list of the nearest 44 stars (including the Sun) is actually a list of 44 multiple systems: 11 of these 44 stars are binaries, and two are triples. In addition, satellites of 7 stars have not yet been seen. These invisible satellites are discovered by disturbances in the proper motions of visible stars. Their masses are close to the masses of the planets of our Solar System and are in the order of magnitude several hundredths of the mass of the Sun, and the largest one has a mass equal to 0.001 solar masses. For example, the companion of the star Ross 614 A has a very small mass, equal to 1/12 the mass of the Sun. American astronomer Willem Leijten discovered a double star, the mass of each component of which is even smaller and hardly reaches 1/25 of the mass of the Sun.

The list of nearest neighbors includes six blue-white stars of very low luminosity, representatives of the class of white dwarfs. These stars make up most interesting group our neighbors; the most famous of them is the satellite of Sirius. Two more are also satellites of bright stars, and the remaining two are . When the satellite of Sirius was discovered, it heat combined with low luminosity, indicated that this was an unusual, and perhaps very rare object. Previously, no one had imagined that there could be stars with masses only slightly less than the mass of the Sun, and with radii barely exceeding the radius of the Earth. In a recently published list of stars located within a radius of no more than 20 pc from the Sun, German astronomer Wilhelm Gliese lists 49 white dwarfs. Research by Leuthen and others has shown that white dwarfs are as common as stars like the Sun. In total, Leuthen has identified about 3,000 “well-established, probable and possible” white dwarfs, which he calls “the easiest stars to identify and the hardest to observe.” The criterion for their identification is large proper motions and a color index comparable to the color index of a class B or A star whose light has not been absorbed.

The apparent magnitude of most known white dwarfs is 14 m. For more than half of the discovered white dwarfs, it was possible to determine spectra and parallaxes, since stars can be plotted on a spectrum - absolute magnitude diagram. They form a branch not entirely parallel to the main sequence, and their absolute values ​​M range from +10 to +15, i.e., their luminosities range from 0.01 to 0.0001 the luminosity of the Sun. Their sizes range from the diameter of Mercury to the diameter of Uranus, i.e. between 1/3 and 4 the diameters of the Earth. Leithen estimates that 5% of all stars appear to be white dwarfs.