Now we, knowing this simple inverse relationshipobject distances and sizes, let's try to take a swing at the “basics of the foundations” and calculate exemplary distance to nearby stars.
Skeptics will immediately say that these optical laws may not work at cosmic distances, so let's first start by checking the known facts: the Sun is 400 times larger than the Moon. The distance from the Earth to the Sun is also well known - about 150 million km. Because in our sky, the Sun and the Moon are visually the same (this is perfectly noticeable in full sun or lunar eclipse), it turns out that the Moon should be closer to us than the Sun by 400 times. And this is also confirmed! Yandex to help us: from the Earth to the Moon 384,467 km! Let's check if the dependence formula works, for this we divide 150 million km by 384467 and get 390 times! Those. it turns out that celestial mechanics works absolutely exactly and the optical law of the inverse dependence of the apparent size of an object on distance is perfectly observed.
Now we need to find a worthy object to study. Of course, it will be our Sun. First, we know the distance to the Sun. Secondly, as scientists tell us, our Sun is just an “ordinary” yellow dwarf and there are a huge number of similar G2 class stars in the sky - about 10% of all stars. And .
Now the most important thing: it turns out that if we have stars in the sky (and they are there), which, according to scientists, are approximately equal to the size of our Sun - now let's drop the conventions, the exact parameters are not so important to us, the important thing is that the star in its approximately the same size as the Sun - i.e. if we know how many times the sun visually larger than this star, we will be able to calculate the real distance to this star! Everything is simple! Complete analogy with the Moon and the Sun.
Now we take a star that has (according to scientists) very close parameters to our Sun: for example, 18 Scorpio (18 Scorpii) - single in the constellation , which is at a distance of about 45,7 from the earth. The object is remarkable in that its characteristics are very similar to .
So, "By the star belongs to the category and is a doppelgänger : mass - 1.01 solar masses, radius - 1.02 solar radii, luminosity - 1.05 solar luminosities”...
Let me explain, this star 18 Scorpio can be seen in the sky with the naked eye. In any case, if scientists were able to describe the star - apparently by the spectrum - then we will have no doubts - this star is the “double” of our Sun.
There are many more stars that are comparable in size to our daylight. For example, Alpha Centauri, Zeta Reticuli, etc. It is important to understand the main thing: in the sky there are many visible stars, whose dimensions, according to astronomers, are close to those of the Sun.
Now for the thought experiment itself:
We must compare the disk of the Sun and the disk of a star, which, as we know from its size, is its close analogue. How many times the disk of the Sun is larger than the star, how many times the star is farther than the sun (tested by the Moon)!
Let's take a day when the Sun is at its zenith (this is his our visual perception) and try to “estimate” how many times the sun will be larger than its “namesake” (which is visible only at night).
So, suppose that on the visible disk of the Sun at the zenith, 1000 stars can be deposited (from one edge of the disk to the other). In fact, there may be more, but I will assume that because Wiki claims that the vast majority of stars are much smaller than the Sun, which means that among the bright night lights in the night sky there can be quite a lot of “babies”, and this automatically reduces the distance to them - for example, not 1000 times, but only 100 or even less!
Now let's calculate the distance to the star. 150 million * 1000. We get: 150.000.000.000 km. =150 billion km. Now let's calculate how much light it takes to cover this distance. After all, we are told about a minimum of light years !!! So, we know that the speed of light is 300,000 km/sec. So we just divide 150,000,000,000 km by 300,000 km/sec and get the time in seconds: 500,000 sec. That's just 5.787 normal days! Those. the light from such a star will reach us for only a few days ...
Now let's calculate how much you have to fly on a rocket at a speed of, for example, 10 km / s. The answer will be 15 billion seconds. If translated into years, then this is: 475.64 Earth years! Of course, the figure is amazing, but it's still not a light year! This is a light week maximum! Those. the light of the stars that we see in the sky is the most "fresh" that neither is. Otherwise, we would see a black empty sky. But, if we still see it in the stars, then the stars are much closer. If we assume that no more than a hundred stars along the diameter fit in the sun, then flying to the nearest star is only about 50 years!
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Ignore the effects of supernova explosions stars.For example, about the collisions of the Earth ... only in how much far in the past there was the last ... "hairy" or "shaggy" ( star). Meanwhile, this word... did not enter... So which at us it's a millennium now...
Let's leave our sunny city and set off mentally to travel to the far reaches of the universe.
It has already been said in this book that even in ancient times people called the stars fixed. In fact, the entire firmament revolves around the Earth (now you know that this rotation is apparent). And one star from another is always on the same distance.
Here is the constellation Ursa Major. What figure its seven stars formed two thousand years ago, it is the same now, it will remain the same for several thousand years.
However, the immobility of the stars is apparent: they rush with great speed in the world space, but we do not notice their movements, since the stars are terribly far from us.
For centuries, astronomers have been trying to find out how far the stars are from us, and have been unable to do so.
In 1837, the director of the Pulkovo Observatory, V. Ya. Struve, managed to find the distance to the star Begi. It turned out that this star is about 1700 thousand times farther from us than the Sun!
It was important to take the first step. Simultaneously with Struve and later, scientists found the distance to many stars.
Astronomers have named the star closest to us Proxima, in Latin it means “Nearest”. Proxima (it is located in the constellation Centaurus) is a small star, it is visible only in a good telescope and only from the southern hemisphere of the Earth.
Let's calculate how soon we can get to Proxima.
And where are we going?
Imagine a fantastic picture.
A rail track has been laid to Proxima, and the first passenger train is waiting for a signal to depart. You and I, out of breath, run to the checkout.
- Any more tickets to Proxima?
- Please. - calmly answers the cashier.
- Two tickets!
- Pay money.
- How much?
“Now I’ll count,” the cashier says. - Since the path is long, the authorities of the road set a price favorable to the public: one ruble for every million kilometers.
- It's a real gift! We are delighted to be surprised.
- Wait a bit! the cashier smiles. - So, one ruble per million kilometers is one hundred and fifty rubles per astronomical unit. And to Proxima, two hundred and sixty thousand astronomical units, which means ... thirty-nine million rubles from you, citizens!
We back away from the cash register in fright.
- And ... and how long will the train go?
“Now let’s calculate this as well,” the cashier reassures us. - We send express - three hundred kilometers per hour. The path to the Sun would take fifty-eight years, and to Proxima two hundred and sixty thousand times further ... In fifteen million years you will reach the goal, comrades!
- Will there be stations along the way?
- Hardly ... Unless some kind of comet will fall.
We embarrassedly back away from the cash register.
We'll come back next time when we're free...
The cashier looks after us sadly.
- Apparently, the flight will not take place. All passengers flee...
It turns out that a train for interstellar travel is completely inappropriate. We remember the rocket. Let us suppose that a fuel has already been invented that makes the rocket move at 20 kilometers per second, 72,000 kilometers per hour.
Now you and I will find out that it is not at all more profitable to fly on a rocket. The speed of the rocket is 240 times the speed of the train, which means that it will take 240 times less time. Divide 15 million by 240.
Though! Even a rocket will have to fly 62,500 years. How far are the stars from us!
This book has already said that the fastest thing in the world is a light beam. Every second he runs a distance of 300 thousand kilometers - almost as much as from the Earth to the Moon. Now if only to travel on a light beam!
The distance from the Earth to the Sun, that is, one astronomical unit, the light beam will run in 8 minutes 20 seconds. There are 1440 minutes in a day, which is 173 times more than 8 minutes 20 seconds. This means that in a day light travels about 173 astronomical units, and in a year it travels 63,000 astronomical units, that is, a path that is 63,000 times greater than the distance from the Earth to the Sun.
The distance that light travels in a year is called a light year by astronomers, and this huge measure of length measures distances in the universe.
Indeed, the astronomical unit is good for solar system, and when it comes to stellar distances, it becomes quite small. Even to Proxima, 260 thousand astronomical units, but there are stars that are thousands and even millions of times further from the Earth. Measuring the distance to such stars in astronomical units is like measuring the distance from Moscow to Vladivostok in millimeters.
Remember firmly: a year is a measure of time, 365 and a quarter of a day; a light year is a measure of length, 63,000 astronomical units.
How many light years to Proxima? There are 63,000 astronomical units in one light year, and in total there are 260 thousand astronomical units before Proxima - this means that it is more than four light years away. oskakkah.ru - site
Here is another fantastic scene.
An expedition sent from Earth to Proxima got there. Travelers have taken with them a powerful radio transmitter and are talking to the Earth.
- Hello Hello! Proxima speaking! Earth, can you hear us?
- Hello, hello, says the Earth! We hear Proxima well! How was the journey?
- Very good! There were no major incidents along the way. We are waiting for people and food to be sent.
"Didn't you find habitable planets there?"
- Haven't found it yet. They settled temporarily on one small planet, but nature on it is scarce and food is not suitable for earthly stomachs.
- All right, we'll send passenger and transport ships. This is where we end the conversation. Goodbye, Proxima!
- Goodbye, Earth!
How long do you think this little conversation will take? Over 25 years! More than eight years will pass between each question and getting an answer to it, since radio waves travel through space at the same speed as light.
Light with its colossal speed, 300 thousand kilometers per second, rushes from Proxima to us for more than four years. And there are stars that are immeasurably further away.
The Universe is immense! And it is almost impossible to imagine how far even the nearest stars are from us. Perhaps stories about the train, about the rocket, and about talking on the radio will help you.
How small the universe was imagined by the ancients!
In one ancient Greek legend, it is said that the god Hephaestus dropped an anvil from the sky, and it flew to the Earth for nine days and nine nights. To the ancient Greeks, this distance seemed incredibly large, and a falling object will pass only 580 thousand kilometers in nine days - this is a little further than from the Earth to the Moon.
Even the solar system is thousands of times larger than the entire universe in the view of the Greeks.
Many stars are much larger than the sun
Rays of light coming from the stars
astronauts in orbit
Before going to bed, I really like to look at the beauty starry sky. It seems that there, above - the kingdom of eternal peace and quiet. Just reach out your hand, and the star is in your pocket. Our ancestors believed that the stars could influence our destiny and our future. But not everyone will answer the question of what they are. Let's try to figure it out.
Stars are the main "population" of galaxies. For example, there are more than 200 billion of them shining in our galaxy alone. Each star is a huge hot luminous ball of gas, like our Sun. A star shines because it releases an enormous amount of energy. This energy is generated as a result of nuclear reactions at very high temperatures.
Many of the stars are much larger than the Sun. And our Earth is a speck of dust compared to the Sun! Imagine that the Sun is a soccer ball, and our planet Earth is as small as a pinhead in comparison! Why do we see the Sun so small? It's simple - because it is very far from us. And the stars look very small because they are
much, much further. For example, a ray of light travels the fastest in the world. It can circle the entire Earth before you can blink an eye. So, the Sun is so far away that its beam flies to us for 8 minutes. And the rays from other closest stars fly to us for 4 whole years! Light from the most distant stars flies to the Earth for millions of years! Now it becomes clear how far the stars are from us.
But if the stars are the Suns, then why do they shine so faintly? The farther away the star, the wider its rays diverge, and the light is scattered throughout the sky. And only a tiny portion of these rays reaches us.
Although the stars are scattered throughout the sky, we see them only at night, and during the day against the background of a bright scattered light in the air. sunlight they are not visible. We live on the surface of the planet Earth and seem to be at the bottom of the ocean of air, which constantly worries and seethes, refracting the rays of the light of stars. Because of this, they seem to us to blink and tremble. But astronauts in orbit see the stars as colored non-blinking dots.
The world of these celestial bodies is very diverse. There are giant stars and supergiants. For example, the diameter of the star Alpha is 200 thousand times larger than the diameter of the Sun. The light of this star travels the distance to the Earth in 1200 years. If it were possible to fly around the giant's equator by plane, then this would take 80 thousand years. There are also dwarf stars, which are significantly inferior in size to the Sun and even the Earth. The matter of such stars is characterized by extraordinary density. Thus, one liter of Kuiper's "white dwarf" matter weighs about 36,000 tons. A match made from such a substance would weigh about 6 tons.
Take a look at the stars. And you will see that they are not all the same color. The color of a star depends on the temperature on their surface - from several thousand to tens of thousands of degrees. Red stars are considered "cold". Their temperature is "only" about 3-4 thousand degrees. The surface temperature of the Sun, which is yellow-green in color, reaches 6,000 degrees. White and bluish stars are the hottest, their temperature exceeds 10-12 thousand degrees.
This is interesting:
sometimes you can watch the stars fall from the sky. They say that when you see a shooting star, you need to make a wish, and it will surely come true. But what we think of as shooting stars are just little rocks coming from outer space. Approaching our planet, such a stone collides with an air shell and, at the same time, becomes so hot that it begins to glow like an asterisk. Soon the "asterisk", not reaching the Earth, burns out and goes out. These "space aliens" are called meteors. If part of the meteor reaches the surface, then it is called a meteorite.
On some days of the year, meteors appear in the sky much more often than usual. This phenomenon is called meteor shower or they say that it is "raining stars".
The ancients believed that all the stars were at the same distance from the Earth, attached to a crystal sphere. In ancient times, the Earth was considered the fixed center of the universe, around which the sun, moon, planets and stars revolved. The nature of the celestial bodies was unknown at that time, and only a very few philosophers believed that the stars were, in fact, distant suns.
This idea began to spread only after the appearance of the teachings of Copernicus in the 16th century. To explain the irregularities in the movement of the planets across the sky, Copernicus suggested that the center of the universe is not the Earth, but the Sun, around which the planets revolve. The Earth, having lost the status of the center, became just one of the planets: now it did not rest motionless, but revolved around the Sun in an orbit. Then some scientists had the idea to measure the distances to the stars. The method they proposed is called the annual parallax method.
The idea was simple and was as follows. If you constantly measure the position of a star in the sky, you can see how the star describes tiny ellipses in space with a period of 1 year. The displacement of the star must occur due to the movement of the Earth in orbit around the Sun, and its magnitude will be the greater, the closer the star is to us. Knowing the magnitude of the displacement angle or, in other words, the parallax of a star, one can easily find the distance to it using the formula D=a/sin(p), where a is the semi-major axis of the earth's orbit, and p is the parallax value, measured in seconds of arc.
Despite the simplicity of the method, scientists have not been able to detect parallaxes in stars for a long time. Some considered this to be evidence of the fallacy of the Copernican theory, but most believed that the stars were simply too far away from us to hope to determine their parallax.
Only in the 19th century, with the advent of a new generation of telescopes that could measure very small angles, were scientists able to reliably determine the distances to some stars. Parallax was first measured by the great Russian astronomer, the first director of the Pulkovo Observatory, Vasily Yakovlevich Struve in 1837. Observing the star Vega, he found that its parallax is 0”, 125. It's a completely negligible angle. Suffice it to say that at such an angle a person will be visible to the naked eye from a distance of 3000 kilometers!
Now it was possible to calculate the distance to this star. If the distance from the Earth to the Sun (a) is taken as 1, then D = 1 / sin (0”, 125), which is equal to 1650000. This figure shows how many times Vega is farther from the Earth than the Sun. It is inconvenient to measure such colossal distances in kilometers, so astronomers use parsecs. A parsec is the distance from which the semi-major axis of the Earth's orbit, perpendicular to the line of sight, is visible at an angle of 1 ". The distance in parsecs is equal to the reciprocal of the parallax. Since Vega's parallax is only 1/8 of a second of arc, the distance to the star is 8 parsecs.
This is a very large value. Light, moving at a speed of 300,000 km/s, will overcome this distance in 26 years. This means that the Vega light we observe was emitted by the star 26 years ago!
To date, scientists know the parallaxes of more than a hundred thousand stars. The method of annual parallaxes allowed astronomers to determine the exact distances to stars within a radius of about a hundred parsecs or 320 light years from the Sun. Distances to more distant stars are determined by other, indirect methods. But they are based on the same annual parallax method.
How often do we look enchanted into the sky, amazed by the beauty of twinkling stars! They seem to be scattered across the sky and beckon us with their mysterious glow. Many questions arise in this case, but one thing is clear: the stars are very far away. But what is behind the word "very"? How far are the stars from us? How can you measure the distance to them?
But first, let's deal with the very concept of a "star".
What does the word "star" mean?
The star is heavenly body(a material object naturally formed in outer space) in which thermonuclear reactions take place. A thermonuclear reaction is a type of nuclear reaction in which the lungs atomic nuclei combined into heavier ones due to kinetic energy their thermal motion.
Our Sun is a typical star..
Simply put, stars are huge luminous gas (plasma) balls. They are formed mainly from hydrogen and helium by interaction - gravitational compression. The temperature in the depths of the stars is huge, it is measured in millions of kelvins. If you like, you can convert this temperature to degrees Celsius, where °C = K−273.15. On the surface, it is, of course, lower and amounts to thousands of kelvins.
Stars are the main bodies of the Universe, because they contain the bulk of the luminous matter in nature.
With the naked eye, we can see about 6,000 stars. All of these visible stars (including those visible with telescopes) are in the local group of galaxies (i.e. galaxies Milky Way, Andromeda and Triangulum).
Closest to the Sun is the star Proxima Centauri. It is located at 4.2 light year from the center of the solar system. If this distance is converted into kilometers, then it will be 39 trillion kilometers (3.9 10 13 km). A light year is equal to the distance traveled by light in one year - 9,460,730,472,580,800 meters (or 200,000 km/s).
How is the distance to stars measured?
As we have already seen, the stars are very far from us, so these huge luminous balls appear to us as small luminous points, although many of them can be many times larger than our Sun. It is very inconvenient to operate with such huge numbers, so scientists have chosen a different, relatively simple way to measure the distance to stars, but less accurate. To do this, they observe a certain star from two poles of the Earth: south and north. In such an observation, the star is shifted a small distance for the opposite observation. This change is called parallax. So, parallax is a change in the apparent position of an object relative to a distant background, depending on the position of the observer.
We see this in the diagram.
The photo shows the phenomenon of parallax: the reflection of the lantern in the water is significantly shifted relative to the practically unshifted Sun.
Knowing the distance between observation points D ( base) and offset angle α in radians, you can determine the distance to the object:
For small angles:
To measure the distance to stars, it is more convenient to use the annual parallax. annual parallax- the angle at which the semi-major axis of the earth's orbit is visible from the star, perpendicular to the direction to the star.
Annual parallaxes are indicators of distances to stars. Distances to stars are conveniently expressed in parsecs. (ps). A distance whose annual parallax is 1 arc second is called parsec(1 parsec = 3.085678 10 16 m). The nearest star, Proxima Centauri, has a parallax of 0.77″, so the distance to it is 1.298 pc. The distance to the star α Centauri is 4/3 ps.
Even Galileo Galilei suggested that if the Earth revolves around the Sun, then this can be seen from the variability of parallax for distant stars. But the instruments that existed then could not detect the parallactic displacement of stars and determine the distances to them. And the radius of the Earth is too small to serve as a basis for measuring the parallactic displacement.
The first successful attempts to observe the annual parallax of stars were made by an outstanding Russian astronomer V. Ya. Struve for the star Vega (α Lyra), these results were published in 1837. However, scientifically reliable measurements of the annual parallax were first carried out by a German mathematician and astronomer F. V. Bessel in 1838 for the star 61 Cygnus. Therefore, the priority of discovering the annual parallax of stars is given to Bessel.
By measuring the annual parallax, one can reliably determine the distances to stars that are no further than 100 ps, or 300 light years. Distances to more distant stars are currently determined by other methods.
