Distances to the stars. Are the stars far from us? How far are the stars from us

And other planets. Looking at the sky, they were able to establish that the Moon, moving across the sky, obscures one or another star, but the stars themselves are never in front. Sometimes the planets obscure the stars. This suggests that the stars are located farther than the planets.

But what next? even then he pointed out that the stars are very far from the Earth and therefore we cannot notice the displacement of the positions of the stars. But they must necessarily be due to the movement of the Earth together with the stars in world space.

Astronomers could not see such movements of stars about three centuries after. Although during that period great advances were made in the invention of instruments for observing the sky, as well as in the accuracy of observations. In the middle of the XVIII century. famous scientists Bradley (in England) and Lambert (in Germany) found that the distances to the stars closest to us are many times greater than the distances from the Earth to. But they did not succeed in knowing exactly the distances to the stars.

For the first time in the history of science, V. Ya. Struve measured . He measured the position of Vega many times and came to the conclusion that Vega is displaced in half a year by an angle of about 1/4 of an arc second. At such a small angle from Vega, the diameter of the earth's orbit should be visible - in other words, double the distance from the Earth to the Sun, and this distance itself - at an angle of 1/8 of an arc second.

It is known that the circle is divided into 360 degrees with 60 minutes of arc in each degree, each minute is 60 seconds. This means that there are 1,296,000 arc seconds in a circle.

If the radius of the earth's orbit from Vega is at an angle of about 1/8 of a second, or about 1/10,000,000 of a circle (astronomers call this angle the parallax of a given star), then the distance to this star is almost 250 trillion kilometers.

Such numbers are, of course, inconvenient to use. Usually in such cases, astronomers use larger units of length. For example light year. This is a short term for the distance that a light beam travels over a period equal to an Earth year at a speed of about 300,000 km / s. A light year is approximately 9.5 trillion kilometers. Briefly, it can be written as follows: 9.5 x 10 to the 12th power of km.

Astronomers also use a different system for measuring distances to stars. If a circle contains 1,296,000 arc seconds, then a radian is 206,265 arc seconds (57°.3). If the radius of the Earth's orbit were visible from some celestial body at an angle of 1 second of the circle, then this would indicate that the distance to such a body is 206,265 times greater than the radius of the Earth's orbit, and is equal to approximately 31 trillion km or 374 light year. This value is called parallax-second or parsec.

Vega is located at a distance of 8 parsecs, or 26.5 light years from us. To fly such a distance, the TU-154 aircraft would need forty million years.

Vega is indeed one of the relatively close stars to us, but not the closest. Of the brightest stars, the closest to us is the star alpha in the constellation Centaurus, invisible from the territory of Russia. It can be seen in the southern countries. The light from it takes 4.3 years to reach us.

To date, distances to many thousands of stars have been determined in this way.

But with all the accuracy that astronomers have achieved in measuring stellar parallaxes, this method is applicable only to determine the distances to relatively close stars. For distant stars that are hundreds, thousands and tens of thousands of light years away from us, it is not suitable: the angles turn out to be so negligible (hundredths and thousandths of a second) that they cannot be measured. Astronomers have found other quite reliable ways to measure the distances of more distant stars. As a result, the exact distances to tens of thousands of individual stars are now known, and even more stars can be approximated.

If the stars can be seen from unimaginably large distances, then they must have a huge luminosity (luminosity). Stars are very distant suns from us. Some of them emit much more light than our huge

In May 2015, the Hubble telescope recorded an outburst of the most distant, and therefore the oldest known galaxy to date. The radiation took as much as 13.1 billion light years to reach the Earth and be recorded by our equipment. According to scientists, the galaxy was born about 690 million years after the Big Bang.

One would think that if the light from the galaxy EGS-zs8-1 (namely, such an elegant name was given to it by scientists) flew to us for 13.1 billion years, then the distance to it would be equal to that which the light will travel in these 13 .1 billion years.

But we must not forget some features of the structure of our world, which will greatly affect the calculation of the distance. The fact is that the universe is expanding, and it does so with acceleration. It turns out that while light traveled 13.1 billion years to our planet, space expanded more and more, and the galaxy moved away from us faster and faster. A visual process is shown in the figure below.

Given the expansion of space, the most distant galaxy EGS-zs8-1 is currently approximately 30.1 billion light years away from us, which is a record among all other similar objects. Interestingly, until a certain point, we will discover more and more distant galaxies, the light of which has not yet reached our planet. It is safe to say that the record of the EGS-zs8-1 galaxy will be broken in the future.

It is interesting: there is often a misconception about the size of the universe. Its width is compared with its age, which is 13.79 billion years. This does not take into account that the universe is expanding with acceleration. According to rough estimates, the diameter of the visible universe is 93 billion light years. But there is also an invisible part of the universe, which we will never be able to see. Read more about the size of the universe and invisible galaxies in the article "".

If you find an error, please highlight a piece of text and click Ctrl+Enter.

The Milky Way is the galaxy in which the Earth is located.
all the stars in the solar system and all the stars visible to the naked eye
Panorama of the Milky Way taken in Death Valley, USA, 2005
Photo: National Park Service
The mass of the star Deneb is 200 times the mass of the Sun. Earth is more than a thousand light years away. This means that the light of Deneb that we see was emitted somewhere between the birth of the Roman Republic and the fall of the Western Roman Empire. Entertaining facts from the life of stars lists KIRI2LL. On the boundless expanses of the Internet, I somehow stumbled upon the following picture.
Of course, this small circle in the middle of the Milky Way is breathtaking and makes you think about many things, from the frailty of being to the boundless size of the universe, but still the question arises: how much is all this true?

Unfortunately, the compilers of the image did not indicate the radius of the yellow circle, and estimating it by eye is a dubious exercise. However, the @FakeAstropix tweeters asked the same question as me and claim that this picture is correct for about 99% of the stars visible in the night sky.
Another question is, how many stars can be seen in the sky without using optics? It is believed that up to 6000 stars can be observed from the surface of the Earth with the naked eye. But in reality, this number will be much less - firstly, in the northern hemisphere we will physically be able to see no more than half of this number (the same is true for residents of the southern hemisphere), and secondly, we are talking about ideal observation conditions, which in reality are practically impossible to reach. That alone is worth one light pollution of the sky. And when it comes to the most distant visible stars, in most cases, in order to notice them, we need exactly ideal conditions.

But still, which of the small twinkling points in the sky are the most distant from us? Here's the list I've managed to put together so far (although of course I wouldn't be surprised if I missed a lot, so don't judge too harshly).

Deneb- the brightest star in the constellation Cygnus and the twentieth brightest star in the night sky, with an apparent magnitude of +1.25 (it is believed that the limit of visibility for the human eye is +6, a maximum of +6.5 for people with really excellent eyesight). This blue-white supergiant, which lies between 1,500 (latest estimate) and 2,600 light-years away from us - thus the light of Deneb we see was emitted somewhere between the birth of the Roman Republic and the fall of the Western Roman Empire.
Here and below, it should be borne in mind that, due to the small parallax, it is quite difficult to calculate the exact distance to such distant objects, because different sources can give different numbers.

The mass of Deneb is about 200 times the mass of our star than the Sun, and the luminosity exceeds the solar minimum by 50,000 times. If he were in the place of Sirius, he would sparkle in our sky brighter than the full moon.

VV Cephei Ais one of the largest stars in our galaxy. According to various estimates, its radius exceeds the solar one from 1000 to 1900 times. It is located at a distance of 5000 light years from the Sun. VV Cepheus A is part of a binary system - its neighbor is actively pulling the matter of the companion star onto itself. The apparent stellar magnitude VV of Cepheus A is approximately +5.
P Cygnuslocated at a distance of 5000 to 6000 light years from us. It is a bright blue variable hypergiant whose luminosity is 600,000 times that of the sun. Known for the fact that during the period of its observations, its apparent magnitude changed several times. The star was first discovered in the 17th century, when it suddenly became visible - then its magnitude was +3. After 7 years, the brightness of the star has decreased so much that it is no longer visible without a telescope. In the 17th century, several more cycles of a sharp increase followed, and then the same sharp decrease in luminosity, for which it was even called the constant nova. But in the 18th century, the star calmed down and since then its magnitude has been approximately +4.8.

P Cygnus dressed in red

Mu Cepheialso known as Herschel's Garnet Star, is a red supergiant, perhaps the largest star visible to the naked eye. Its luminosity exceeds that of the sun by 60,000 to 100,000 times, and the radius, according to recent estimates, may be 1,500 times that of the sun. Mu Cephei is located at a distance of 5500-6000 light years from us. The star is at the end of its life path and will soon (by astronomical standards) turn into a supernova. Its apparent magnitude varies from +3.4 to +5. It is believed to be one of the reddest stars in the northern sky.

Plaskett's Staris located at a distance of 6600 light-years from Earth in the constellation Monoceros and is one of the most massive systems of double stars in the Milky Way. Star A has a mass of 50 solar masses and a luminosity 220,000 times that of our star. Star B has about the same mass, but its luminosity is less - "only" 120,000 solar. The apparent magnitude of the star A is +6.05 - which means that theoretically it can be seen with the naked eye.
System This keelis located at a distance of 7500 - 8000 light years from us. It consists of two stars, the main of which is a bright blue variable, is one of the largest and most unstable stars in our galaxy with a mass of about 150 solar masses, 30 of which the star has already managed to drop. In the 17th century, Eta Carina had a fourth magnitude, by 1730 it became one of the brightest in the constellation Carina, but by 1782 it again became very faint. Then, in 1820, a sharp increase in the brightness of the star began and in April 1843 it reached an apparent magnitude of −0.8, becoming for a while the second brightest star in the sky after Sirius. After that, the brightness of Eta Carina plummeted, and by 1870 the star was invisible to the naked eye.
However, in 2007 the star's brightness increased again, reaching magnitude +5 and becoming visible again. The current luminosity of the star is estimated to be at least a million solar and it seems to be the main candidate for the title of the next supernova in the Milky Way. Some even believe that it has already exploded.
Rho Cassiopeiais one of the most distant stars visible to the naked eye. It is an extremely rare yellow hypergiant, with a luminosity half a million times that of the sun and a radius 400 times greater than that of our star. According to the latest estimates, it is located at a distance of 8200 light years from the Sun. Usually its magnitude is +4.5, but on average, once every 50 years, the star dims for several months, and the temperature of its outer layers decreases from 7000 to 4000 degrees Kelvin. The last such case occurred in late 2000 - early 2001. According to calculations, during these few months the star ejected matter, the mass of which amounted to 3% of the mass of the Sun.
V762 Cassiopeiaeis probably the most distant star visible from Earth to the naked eye - at least based on currently available data. Little is known about this star. It is known to be a red supergiant. According to the latest data, it is located at a distance of 16,800 light years from us. Its apparent magnitude ranges from +5.8 to +6, so you can see the star just in ideal conditions.

In conclusion, it is worth mentioning that there have been cases in history when people have been able to observe much more distant stars. For example, in 1987 in the Large Magellanic Cloud, located at a distance of 160,000 light years from us, a supernova broke out, which could be seen with the naked eye. Another thing is that, unlike all the supergiants listed above, it could be observed for a much shorter period of time.

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.

When you look at the sky on a dark night in clear weather, you see many stars. However, almost all of them are in our galaxy, the Milky Way. Even the most distant ones that you can see without a telescope are less than twenty thousand light-years from Earth. It may seem like a gigantic distance, but the cosmos is much larger than our immediate surroundings. It is really huge, which is why it is incredibly difficult for scientists to study stars outside our galaxy. The most distant star that has been isolated from the extraneous glow surrounding it is only 55 million light-years away from us.

Scientific achievements

However, if astronomers are not mistaken in anything, this record was recently broken. According to an article published in March this year in the journal Nature Astronomy, he was smashed to smithereens, swept away and trampled. He moved on to a star that is 14 billion light years away from us! It should be noted that astronomers often manage to see objects far from our planet. With telescopes, they can see the brightest supernovae 10 billion light years away. However, ordinary stars cannot be seen even at a distance hundreds of times smaller. And here we first mention about "gravitational lensing".

This phenomenon occurs when the enormous mass of a galaxy, or even a cluster of galaxies, bends, distorts, and amplifies the light behind it. This phenomenon is possible due to the fact that such objects actually bend the very space around them. Galaxies that create the effect of gravitational lensing "amplify" the brightness by an average of 50 times.

distant stars

The star we're talking about today is behind a cluster of galaxies 6 billion light-years away, and its light has been amplified by more than 2,000 times! In scientific catalogs, it is listed as MACS J1149 Lensed Star 1. However, the scientists who discovered it also gave it an unofficial name - Icarus. Thank you very much for this, it is much more convenient for us as well.

Icarus was spotted, quite by accident, when researchers looked at supernova images taken by the Hubble Space Telescope in 2016 and 2017. Not far from her, they noticed a small bright spot. It changed brightness over time, but not in the same way that supernovae do. The color scheme of the light coming from this object remained unchanged for many months. Further analysis showed that we are dealing with a blue supergiant.

These stars are much larger, more massive, hotter than the Sun and hundreds of thousands of times brighter than it. This is such a small reminder that any phenomenon in space can be truly cosmic in scale. All blue supergiants have similar characteristics, therefore, by comparing the light of Icarus with the light of the same objects in our galaxy, astronomers were able to calculate the distance to it. It turned out that the star has an age of 9 billion years, and due to the fact that the Universe is expanding, now the luminaries are generally 14 billion light years before that.

How did Icarus manage to magnify his image by 2000 times when the usual gravitational lensing value is only 50? The answer is microlenses. These are small objects inside large lenses. These can be individual stars, providing an additional approximation of the "picture". Lenses within lenses. This effect does not last long, because the microlenses are constantly moving from the desired position and returning to it again. However, if we carefully follow what is happening, huge opportunities open up before us. With the help of microlensing, scientists have even managed to find planets outside the Milky Way!

the most distant star

Icarus, by the way, can be useful not only as a record holder, listed in the relevant book. By studying how the approach effect affects it over time, astronomers hope to build an accurate model of the distribution of matter in a “lensing” cluster of galaxies. This probably includes dark matter, which we still can’t find, examine and feel, but which has a gravitational effect on other space objects. In this way, Icarus can help us greatly increase our knowledge of the universe. Well, his ancient Greek namesake was also a very positive character, although he did not become a champion, no matter how hard he tried. We hope that our Icarus will not disgrace the glorious name.