The definition of distance in astronomy usually depends on how far away the celestial body is. Some methods can only be applied to relatively close objects, such as neighboring planets. Others are for more distant ones, such as stars or even galaxies. However, these methods are generally less accurate.
How to determine the distance to an object in space
Method for determining the distance to neighboring planets
In the solar system, this is relatively simple: the motion of the planets here is calculated according to Kepler's laws, and the distance of nearby planets and asteroids can be calculated using radar measurements. In this way, it is very easy to set the distance.
Kepler's laws apply inside the solar system
How is the distance to stars measured?
For stars relatively close to us, the so-called parallax can be determined. In this case, it is necessary to observe how the position of the star changes as a result of the revolution of the Earth around our luminary relative to stars that are much more distant from us. Depending on the accuracy of the measurement, a fairly accurate and direct determination of the distance is possible.
Calculating Distances from the Parallax of Stars
If this is not suitable, one can try to determine the type of star from the spectrum in order to infer the distance from the true brightness. This is already an indirect method, since certain assumptions must be made about the star.
Measuring distances from the spectrum of stars
If it is impossible to apply this method, then scientists try to get by with a "scale of distances". At the same time, they are looking for stars whose brightness is precisely known from observations in our Galaxy. Such objects are called "standard candles". They are, for example, Cepheid stars, whose brightness changes periodically. According to the theory, the rate of these changes depends on the maximum brightness of the star.
Calculating distances from Cepheids
If such Cepheids are found in another galaxy and you can observe how the brightness of a star changes, then its maximum brightness is determined, and then the distance from us. Another example of a standard candle is a certain kind of supernova explosion, which astronomers believe always has the same maximum brightness.
A standard candle could be a supernova explosion
However, even this method has its limitations. Then astronomers use the redshift in the spectra of galaxies.
Increasing the wavelength of light coming from a galaxy makes it appear redder in the spectrum, called redshift.
Based on it, the removal rate of a galaxy can be calculated, which is directly related - according to Hubble's law - to the distance to this galaxy from the Earth.
"Very interesting and informative information on how you can determine the distance to an object on the ground using only your own eye. In total, several methods for determining distances on the ground are described, but for our topic of measuring distances to stars, only one of the conclusions is important to us, which says that when an object is removed N times farther than it was from us, it visually decreases N times; and vice versa, how many times we bring the object closer, so many times it visually will increase. Those. if you take an object, measure its physical length (let it be a stick 1 m long), measure the distance to this object (let it be 0.1 m), then remove this object at a distance of 4 m from where it was, then visually it becomes 4 times smaller! Everything is very simple. Knowing this dependence, on the ground it is possible to determine the distance to the object quite accurately, however, you need to know its actual size. But this is not a problem when it comes to a car or a similar well-known object.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 first let's 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 during a total solar 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 own 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 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 1000 stars can be deposited on the visible disk of the Sun at the zenith (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 few “babies”, and this automatically reduces the distance to them - for example, not by 1000 times, but only by 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!
Evaluation of information
Related posts
Neglect 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...
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 they are not visible against the background of bright sunlight scattered in the air. We live on the surface of the planet Earth and are, as it were, 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. So, one liter of substance " white dwarf» Kuiper 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.
It 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 a meteor shower or they say that it is "raining stars".
When observing any star from two opposite points of the globe, it is almost impossible to notice differences in the directions to the star. The stars are many times farther from the Earth than the Moon, the planets, and the Sun. The Russian scientist V. Ya. Struve managed to determine the distance to the nearest star to us. This was over a hundred years ago. To do this, he had to observe it not from the ends of the earth's diameter, but from the ends of a straight line, which is 23,600 times longer. Where could he get such a straight line that cannot fit on the globe? It turns out that this line exists in nature. This is the diameter of the earth's orbit. For half a year Earth takes us to the other side of the sun. Knowing the diameter of the Earth's orbit (and it is twice the average distance to the Sun), by measuring the angles at which the star is observed, you can calculate the distance to it.
The stars closest to us - Proxima Centauri and Alpha Centauri - are 270,000 times farther from the Earth than the Sun. A beam of light from these stars has to fly to the Earth for 4.5 years.
The distances to the stars are huge and it is inconvenient to measure them in kilometers. It turns out too many kilometers. And scientists introduced a larger unit of measure: the light year. This is the distance light travels in one year.
How many times is this unit of measurement greater than a kilometer? 300,000 km/s must be multiplied by the number of seconds in a year. We get approximately 10 trillion kilometers. This means that one light year is 10 trillion times more than one kilometer (10,000,000,000,000).
Stars can be from us at distances equal to tens, hundreds, thousands of light years or more.
The air is as clear during the day as it is at night, but the stars are not visible. The thing is that in the daytime the atmosphere scatters sunlight. Try looking out into the street from a well-lit room in the evening. Through the window glass, the bright lights located outside are visible quite well, and it is almost impossible to see dimly lit objects. But all you have to do is turn off the light...
The river flows quietly and smoothly across the plain, and accelerates its movement on steep cliffs. The stream cuts deep into the soil and forms narrow gorges with steep and high walls. Especially quickly the water erodes the coast, consisting of loose rocks. If the river is blocked by mountains, it either goes around them or breaks through, creating deep gorges and canyons. Sometimes…
The cleanest and deepest lake is Baikal. Its length is 620 kilometers with a width of 32 to 74 kilometers. The depth of the lake in the deepest place - the Olkhon crack - is 1940 meters. The volume of fresh water in the lake is 2300 cubic kilometers. Geographers call Lake Tanganyika the African sister of Baikal. It originated in East Africa many millions ...
Folk Russian wisdom says: "Put a house where the sheep lay down." And in China, there is a custom not to start building a house until you are sure that the building site is free from “deep demons”. That is why most of the ancient cities and villages, both in Russia and in many other countries, are located very well. Although there is, of course,…
The need to measure time arose among people already in ancient times. The first calendars appeared many thousands of years ago at the dawn of human civilization. People have learned to measure periods of time, to compare them with phenomena that recur periodically (change of day and night, change of phases of the moon, change of seasons). Without the use of time units, people could not live, communicate with each other, ...
This constellation has two bright stars are very close to each other. They got their name in honor of the Argonauts Dioscuri - Castor and Pollux - twins, sons of 3eus, the most powerful of the Olympic gods, and Leda, a frivolous earthly beauty, the brothers of Elena the beautiful - the culprit Trojan War. Castor was famous as a skilled charioteer, and Pollux as an unsurpassed fist ...
The great Italian Galileo Galilei (1564-1642), who did a lot for the development of mathematics, mechanics, physics, achieved amazing success in the study of celestial bodies. He became famous not only for a number of astronomical discoveries, but also for the great courage with which he stood up for the teachings of Copernicus, which was forbidden by the all-powerful church. In 1609, Galileo learned that a far-seeing device had appeared in Holland (as it is translated from Greek ...
Solar and lunar eclipses have been familiar to man since ancient times. When a person did not yet know why these phenomena occur, the extinction of the Sun in broad daylight caused him panic fear. It is truly a mysterious and majestic sight. The bright Sun shines on the blue sky and gradually the sunlight begins to weaken. Damage appears on the right edge of the Sun. It is slowly increasing...
But what if our star - the Sun - suddenly bursts into a supernova? Will it disappear itself and erase us from the universe forever? As scientists say, although this event is possible, its probability is very small. The star receives its energy by gradually converting hydrogen into helium, then into heavier elements (carbon, oxygen, neon, and others) using a chain ...
The largest planet is named after the supreme god Olympus. Jupiter is 1310 times larger in volume than Earth and 318 times larger in mass. In terms of distance from the Sun, Jupiter is in fifth place, and in terms of brightness it ranks fourth in the sky after the Sun, Moon and Venus. The telescope shows a planet compressed at the poles with a noticeable row ...
More than six thousand light-years from the surface of the Earth is a rapidly rotating neutron star - the Black Widow pulsar. She has a companion, a brown dwarf, whom she constantly processes with her powerful radiation. They revolve around each other every 9 hours. Watching them through a telescope from our planet, you might think that this deadly dance does not concern you in any way, that you are only an outside witness to this “crime”. However, it is not. Both participants in this action attract you to them.
And you attract them too, trillions of kilometers away, with the help of gravity. Gravity is the force of attraction between any two objects that have mass. This means that any object in our universe attracts any other object in it, and at the same time is attracted to it. Stars, black holes, people, smartphones, atoms - all this is in constant interaction. So why don't we feel this attraction from billions of different directions?
There are only two reasons - mass and distance. The equation that can be used to calculate the force of attraction between two objects was first formulated by Isaac Newton in 1687. The understanding of gravity has evolved somewhat since then, but in most cases, Newton's classical theory of gravity is still applicable to calculating its strength today.
This formula looks like this - to find out the force of attraction between two objects, you need to multiply the mass of one by the mass of the other, multiply the result by the gravitational constant, and divide all this by the square of the distance between the objects. Everything, as you can see, is quite simple. We can even experiment a little. If you double the mass of one object, the force of gravity will double. If you "push" objects away from each other by the same two times, the force of attraction will be one-fourth of what it was before.
The force of gravity between you and the Earth is pulling you towards the center of the planet, and you feel this force as your own weight. This value is 800 Newtons if you are standing at sea level. But if you go to the Dead Sea, it will increase by a small fraction of a percent. If you accomplish the feat and climb to the top of Everest, the value will decrease - again, extremely slightly.
The force of gravity of the Earth acts on the ISS, located at an altitude of about 400 kilometers, with almost the same force as on the surface of the planet. If this station were mounted on a huge fixed column, the base of which would be on the Earth, then the gravitational force on it would be about 90% of what we feel. Astronauts are in zero gravity for the simple reason that the ISS is constantly falling on our planet. Fortunately, the station at the same time moves at a speed that allows it to avoid collision with the Earth.
We fly further - to the moon. This is already 400,000 kilometers from home. The force of gravity of the Earth here is only 0.03% of the original. But the gravity of our satellite is fully felt, which is six times less than we are used to. If you decide to fly even further, the force of gravity of the Earth will fall, but you will never be able to completely get rid of it.
When you are on the surface of our planet, you feel the attraction of a great many objects - both very distant and those in close proximity. The sun, for example, pulls you towards it with the force of half a newton. If you are at a distance of several meters from your smartphone, then you are drawn to it not only by the desire to check received messages, but also by a force of several piconewtons. This is approximately equal to the gravitational pull between you and the Andromeda galaxy, which is 2.5 million light-years away and has a mass trillions of times that of the Sun.
If you want to completely get rid of gravity, you can use a very tricky trick. All the masses that are around us are constantly pulling us towards them, but how will they behave if you dig a very deep hole right to the center of the planet and go down there, somehow avoiding all the dangers that may be encountered along this long path? If we imagine that there is a cavity inside a perfectly spherical Earth, then the force of attraction to its walls will be the same from all sides. And your body will suddenly find itself in weightlessness, in a suspended state - exactly in the middle of this cavity. So you may not feel the gravity of the Earth - but for this you need to be exactly inside it. These are the laws of physics and nothing can be done about them.
