Lesson of the surrounding world on the topic "Why the sun shines during the day, and the stars - at night." Why does the sun shine for so many years? Why does the sun shine for children
The light of the Sun is one of the most important things on earth. It supports life in every organism on our planet, and without it we simply would not exist. But how does it affect us? And why does the sun shine at all? Let's find out how these processes work.
Another star in the sky
In ancient times, people did not know why the sun shines. But even then they noticed that it appears early in the morning and disappears in the evening, and bright stars come to replace it. He was considered a diurnal deity, a symbol of light, goodness and power. Now science has stepped far forward and the Sun is no longer so mysterious to us. Dozens of websites and books will tell you a lot of details about him, and NASA will even show him pictures from space.
Today we can safely say that the Sun is not some special and unique object, but a star. Just like the thousands of others we see in the night sky. But other stars are very far away from us, so from Earth they seem like tiny lights.
The sun is much closer to us, and its radiance can be seen much better. It is the center of the star system. Planets, comets, asteroids, meteoroids and others revolve around it. space bodies. Each object moves in its own orbit. The planet Mercury has the smallest distance to the Sun, the farthest parts of the system have not been explored. One of the distant objects is Sedna, which makes a complete revolution around the star in 3420 years.
Why does the sun shine?
Like all other stars, the Sun is a huge hot ball. It is thought to have formed from the remains of other stars about 4.5 billion years ago. The gas and dust released from them began to compress into a cloud, the temperature and pressure of which constantly increased. Having "warmed up" to about ten million degrees, the cloud turned into a star, which became a giant energy generator.
So why does the sun shine? All this is due to thermonuclear reactions inside it. At the center of our star, hydrogen is continuously converted into helium, under the influence of a very high temperature - about 15.7 million degrees. As a result of this process, a huge amount of thermal energy is produced, accompanied by a glow.
Thermonuclear reactions take place only in the solar core. The radiation it produces spreads around the star, forming several outer layers:
- radiant transfer zone;
- convective zone;
- photosphere;
- chromosphere;
- crown.
Sunlight
Most of the visible light is produced in the photosphere. This is an opaque shell, which is identified with the surface of the Sun. The temperature in Celsius of the photosphere is 5,000 degrees, but there are also "colder" areas on it, called spots. In the upper shells, the temperature increases again.
Our luminary belongs to the yellow dwarfs. This is far from the oldest and not the largest star in the universe. In its evolution, it has reached about half the way and will live in this state for about another five billion years. Then the Sun will turn into a red giant. And then sheds off the outer shell and becomes a dim dwarf.
The light it emits now is almost white. But from the surface of our planet, it is visible yellow, as it dissipates and passes through the layers of the earth's atmosphere. The color of the radiation becomes close to the real one in very clear weather.
Interaction with the Earth
The location of the Earth and the Sun relative to each other is not the same. Our planet is constantly moving around the star in its orbit. It makes a complete revolution in one year or approximately 365 days. During this time, it covers a distance of 940 million kilometers. On the planet itself, movement is not felt, although every hour it passes about 108 kilometers. The consequences of such a journey are manifested on Earth in the form of a change of seasons.
However, the seasons are determined not only by the movement around the Sun, but also by the tilt earth's axis. Relative to the orbit, it is inclined by 23.4 degrees, so different parts of the planet are illuminated and warmed by the star in different ways. When the Northern Hemisphere is turned towards the Sun, it is summer there, and in the Southern Hemisphere at the same time it is winter. Six months later, everything changes exactly the opposite.
We often say that the Sun appears during the day. But this is just an expression, because it creates the day for us. Its rays penetrate the atmosphere, illuminating the planet from morning to evening. Their brightness is so strong that we simply do not see the rest of the stars during the day. At night, the Sun does not stop shining, it's just that the Earth turns to it first one side, then the other, because it rotates not only in orbit, but also around its own axis. It makes a full rotation in 24 hours. On the side turned to the star - day, on the opposite side - night, every 12 hours they change.
Irreplaceable Energy
From our planet, the distance to the Sun is 8.31 light years, or 1.496 10 8 kilometers, which is quite enough for the existence of life. A closer location would make the Earth look like a lifeless Venus or Mercury. However, in a billion years the star should become 10% hotter, and in another 2.5 billion years it will be able to literally dry up all life on the planet.
At present, the temperature of the sun suits us perfectly. Thanks to this, a huge variety of life forms appeared on our planet, ranging from plants and bacteria to humans. They all need sunlight and warmth, and will easily die if left unattended for a long time. The light of the star promotes plant photosynthesis, which produces vital oxygen. Its ultraviolet radiation enhances the functioning of the immune system, promotes the production of vitamin D, and helps to self-purify the atmosphere from harmful substances.
The uneven heating of the Earth by the Sun creates the movement of air masses, which, in turn, creates the climate and weather on the planet. Light from a star affects the establishment of circadian rhythms in living organisms. That is, a strict dependence of their activity on the change of time of day is developed. So, some animals are active only during the day, others only at night.
Sun observation
Among the star systems closest to us, the Sun is not the brightest. It occupies only the fourth place in this indicator. For example, the star Sirius, which is perfectly visible in the night sky, surpasses it in brightness by as much as 22 times.
Despite this, we cannot look at the Sun with the naked eye. It is too close to the Earth and to observe it without special instruments is detrimental to vision. For us, it is about 400 thousand times brighter than the light reflected by the moon. We can look at it with the naked eye only at sunset and dawn, when its angle is small and the luminosity drops by a thousand times.
The rest of the time, to see the Sun, you need to use special solar telescopes or light filters. If at the same time we project the image onto a white screen, then it is possible to see spots and flashes on our star even with non-professional equipment. But this must be done carefully so as not to damage it.
- a fairly common star for Milky Way- not the brightest, not the largest and has an age of only 4.5 billion years. At present, the Sun is the only star known to us whose light and heat support life on the only habitable planet known to us. Fortunately for us, the Sun was still shining at the time when the first people appeared several hundred thousand years ago. But how can the Sun have so much fuel? Why hasn't it gone out yet, like a candle or a fire? And when will our star finally burn out?
Why does the sun shine?
This question was raised by scientists already in the 19th century. At that time, scientists knew only two ways that the Sun could generate energy: either it created heat and light as a result of gravitational contraction - it contracted towards the center and radiated energy (in the form of heat that we feel on), so over time it would become decrease. Either the Sun burned literally like coal in a furnace - as a result chemical reaction, familiar to all of us, and arising when we kindle a fire. Taking as a basis the fact that any of the above hypotheses could support the explanation of the functioning of the Sun, scientists of those years accurately calculated how long our luminary could exist if a corresponding process took place on it. But none of the results matched the figure that the researchers knew about the age - 4.5 billion years. If the Sun were shrinking or burning, it would have been out of fuel long before we entered the evolutionary scene. It became obvious that something else was happening on the Sun.
Einstein's equation
Decades later, armed with Enschnein's famous equation E = mc2, which predicted that any mass must have an equivalent amount of energy, British astronomers in the 1920s suggested that the Sun was actually converting its mass into energy. However, instead of a furnace that turns wood and coal into ash and blackened carbon (radiating light and heat), the center of the Sun looks more like a giant nuclear power plant.
Fusion Fuel of the Sun
The sun contains a huge amount of hydrogen atoms. Typically, a neutral hydrogen atom contains a positively charged proton and a negatively charged electron that orbits around it. When that atom meets another hydrogen atom, their respective outer electrons magnetically repel each other. This prevents one of the protons from meeting each other. But the Sun's core is so hot and under such pressure that the atoms move with great kinetic energy, which allows them to overcome the force that binds their structure, and the electrons begin to separate from their protons. This means that protons normally found inside the nucleus of a hydrogen atom can touch each other and combine into the nuclei of other elements in a process called thermonuclear fusion. This reaction takes place with the release of an enormous amount of energy.
Just like inside nuclear reactor, the atoms inside the Sun's core crash into each other every second. As a result of such collisions, what most often happens is that four hydrogen protons fuse with each other to create one helium atom. As a result of this fusion, some of the mass of these four microscopic protons is “lost”, since the helium atom weighs less than four protons in total. But because the universe retains matter, it can't just disappear forever, this mass is converted into an incredible amount of energy - every second the Sun radiates 3.9 × 10 to the power of 26 watts of power. (This is such a huge amount of energy that, frankly, there is no analogy with terrestrial processes. Perhaps this number can be estimated as follows: this number of watts is much more than all the electricity that the whole world will spend at the current rate of more than a few hundred thousand centuries).
How long will the sun burn?
Reaction efficiency thermonuclear fusion is the main reason why the sun constantly radiates heat - the energy released by converting just one kilogram of hydrogen into helium is equivalent to that released by burning 20,000 tons of coal. Since the Sun is quite massive and relatively young, it is believed that it has used only about half of its fuel - hydrogen.
Eventually, the Sun's core will convert all of its hydrogen into helium, and the star will die. But don't worry. This will not happen for about 5 billion years.
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Finding the Limits of Possibility Hubble telescope, an international team of astronomers has broken the space observation distance record by measuring the properties of the most distant galaxy previously observed in the universe. This unexpectedly bright nascent galaxy, named GN-z11, is visible as it was 13.4 billion years ago, just 400 million years after the Big Bang. Galaxy GN-z11 is located in the constellation Ursa Major.
“We have taken the largest step back in time, beyond what we thought was possible with the Hubble telescope. We see the galaxy GN-z11 at a time when the age of the universe was only three percent of the current. said principal investigator Pascal Hoesch of Yale University.
Astronomers have approached the first galaxies to form in the universe. Hubble's new observations are taking researchers into areas previously thought only reachable with the James Webb Space Telescope (scheduled to launch in 2018).
The measurements provide compelling evidence that some of the unusual and unexpectedly bright galaxies previously seen in Hubble images are actually at extreme distances. Previously, a team of scientists estimated the distance to GN-z11 by determining its color using Hubble and the Spitzer Space Telescope. Now, for the first time in a galaxy at such an extreme distance, the team has used Hubble's Wide Field Camera-3. To accurately measure the distance to the GN-z11, the light was spectroscopically separated into its component colors.
Astronomers measure large distances by determining the "redshift" of a galaxy. This phenomenon is the result of the expansion of the universe. Every distant object in the universe appears to be moving away from us because its light is stretched into longer, redder light waves as it travels through expanding space to reach our telescopes. The greater the redshift, the farther away the galaxy.
"Our spectroscopic observations show that the galaxy is farther away than we originally thought, right at the limit of the distance that Hubble can observe," says Gabriel Brammer, co-author of the study from the Space Telescope Institute.
Before astronomers measured the distance to the galaxy GN-z11, the largest distance measured spectroscopically was a redshift of 8.68 (13.2 billion years into the past). The team has now confirmed a redshift of 11.1 for GN-z11, about 200 million years closer to big bang. “This is an outstanding achievement for Hubble. He managed to break all previous distance records held for years by larger ground-based telescopes, ”says researcher Pieter van Dokkum from Yale University. “This new record will likely stand until the launch of the James Webb Space Telescope.”
The GN-z11 galaxy is 25 times smaller than the Milky Way, and contains only one percent of the mass of our galaxy in its stars. However, the newborn GN-z11 is growing rapidly, forming new stars about 20 times faster than our galaxy is today. This makes the extremely distant galaxy bright enough for astronomers to conduct detailed studies with the Hubble and Spitzer telescopes.
Research results provide surprising clues to nature early universe. “It's amazing that such a massive galaxy exists only 200 or 300 million years after the formation of the very first stars. This requires very rapid growth producing stars at a monstrous rate to form a galaxy of a billion solar masses so quickly,” explains Garth Illinworth, a researcher at the University of California.
These discoveries are a fascinating preview of what the James Webb Space Telescope will be doing after its 2018 launch into space. “This new discovery shows that the Webb telescope will certainly find many of these young galaxies by looking where the first galaxies form,” says Illingworth.
The research team includes scientists from Yale University, the Space Telescope Science Institute and the University of California.
This video shows the location of the galaxy GN-z11 in the visible sky.
The peculiar blue bubble surrounding the star WR 31a is the Wolf-Rayet Nebula, an interstellar cloud of dust, hydrogen, helium and other gases. Such nebulae usually have a spherical or ring shape. They arise when a fast stellar wind interacts with the outer layers of hydrogen ejected by Wolf-Rayet stars. This bubble, which formed about 20,000 years ago, is expanding at about 220,000 kilometers per hour!
Unfortunately, life cycle the Wolf-Rayet star lasts only a few hundred thousand years - a moment on a cosmic scale. Beginning its life with a mass of at least 20 times that of the sun, a Wolf-Rayet star loses half its mass in less than 100,000 years.
And the star WR 31a in this case is no exception. In the end, she will end her life with an impressive flash, and the stellar material ejected by the explosion will become the basis for the next generation of stars and planets.
Despite the simple wording of the question “Why does the Sun shine?” the answer to it requires some base of physical knowledge and to state it in one sentence is a difficult task. We will try to solve it towards the end of the article, which we will begin with a historical background.
Story
One of the first who tried to approach the explanation of the nature of the Sun from a scientific point of view was the ancient Greek astronomer and mathematician Anaxagoras, according to whom the Sun is a hot metal ball. For this, the philosopher was imprisoned. Before the instrumental study of the Sun began in the 17th century, there were still many assumptions about the nature of sunlight, up to the constantly burning forests located on the surface.
Since the 17th century, scientists have discovered such a phenomenon as sunspots, it becomes possible to calculate the period of rotation of the Sun. It becomes clear that our star is a kind of physical body with a complex structure. In the 19th century, spectroscopy arose, with the help of which it was possible to decompose the sun's ray into its component colors. Thus, thanks to the absorption lines, Fraunhofer manages to discover a new chemical element, which is part of the star, is helium.
In the middle of the 19th century, scientists were already trying to describe the glow of the Sun with more complex scientific hypotheses. So Robert Mayer suggested that the star is heated by the bombardment of meteorites. Somewhat later, in 1853, a more plausible idea arose of the so-called "Kelvin-Helmholtz mechanism", according to which the Sun was heated due to gravitational contraction. However, in this case, the age of the luminary would be much less than in reality, which contradicted some geological studies.
Why does the sun shine
The British physicist Ernest Rutherford was the first to come up with the correct answer to this question, who suggested that radioactive decay occurs in the Sun and that it is the source of the star's energy. Later, in 1920, the English astrophysicist Arthur Eddington developed Rutherford's idea, arguing that a thermonuclear fusion reaction can proceed in the core of the Sun under the influence of the internal pressure of the Sun's own mass. After 10 years, the main fusion reactions were calculated, generating the observed amount of energy.
Briefly, the thermonuclear reaction due to which the Sun shines can be described as the fusion of protons (hydrogen nuclei) into a helium-4 nucleus. Since the helium-4 nucleus has a smaller mass than the hydrogen nucleus, the energy difference (free energy) is emitted in the form of photons - particles that are electromagnetic radiation.
thermonuclear reaction
Proton-proton thermonuclear fusion reactions occurring inside stars with a mass of the Sun or less can be divided into three chains: ppI, ppII, ppIII. Of these, ppl accounts for more than 84% of the solar energy. The proton-proton reaction consists of three cycles, where the role of the first is the interaction of two protons (two hydrogen nuclei). With enough energy to overcome the Coulomb barrier, two protons fuse to form a deuteron. Since the deuteron nucleus, consisting of two protons, has less mass than two individual protons, free energy is formed, due to which a positron and an electron neutrino are created, which are emitted from the region where the reaction took place.
Further, due to the interaction of a deuteron and another proton, helium-3 is formed with the release of energy in the form electromagnetic radiation. The further stages of the reaction can be clearly seen in the diagram below.
Reactions inside the sun
In addition to the proton-proton thermonuclear fusion reaction, a small contribution to the energy released by the Sun is made by a reaction of the proton-electron-proton type 0.23%.
Thus, summarizing the above, the Sun radiates electromagnetic waves of various frequencies, including in the visible light region, which are formed by particles born as a result of the released energy during the proton-proton (proton-electron-proton) thermonuclear fusion reaction.
A growing man is interested in literally everything. He asks questions about everything he sees. Why does the sun shine during the day and the stars at night? And so on and so forth. Answering seemingly simple questions is not always easy. sometimes there is a lack of special knowledge. And how to explain the complex in a simple way? Not everyone can do this.
What is a star?
Without this concept, it is impossible to clearly explain why the sun shines during the day, and the stars at night. Often, the stars appear to babies as small dots in the sky, which they compare to small light bulbs or flashlights. If we draw an analogy, then they can be compared with huge searchlights. Because the stars are unimaginably huge, incredibly hot and located at such a distance from us that they seem like crumbs.
What is the sun?
First you need to say that the Sun is a name, like a name. And this name is the closest star to our planet. But why isn't she a dot? And because of what the sun shines during the day, and the stars at night, if they are the same?
The sun does not appear to be a dot because it is much closer than the others. Although it is also far from it. If you measure the distance in kilometers, then the number will be equal to 150 million. A car will cover such a distance in 200 years if it moves without stopping at a constant speed equal to 80 km/h. Because of the incredibly large distance, the sun seems small, although it is such that it could easily contain a million planets like Earth.
By the way, the sun is far from the largest and not very bright star in our sky. It is simply located in one place with our planet, and the rest are scattered far in space.
Why is the sun visible during the day?
First you need to remember: when does the day begin? The answer is simple: when the sun begins to shine from behind the horizon. Without his light, this is impossible. Therefore, answering the question of why the sun shines during the day, we can say that the day itself will not come if the sun does not rise. After all, as soon as it goes beyond the horizon, evening comes, and then night. By the way, it is worth mentioning that it is not the star that moves, but the planet. And the change of day to night occurs due to the fact that the planet Earth rotates around its fixed axis without stopping.
Why, then, are the stars not visible during the day, if, like the sun, they always shine? This is due to the fact that our planet has an atmosphere. They scatter in the air and overshadow the faint glow of the stars. After its setting, the scattering stops, and nothing blocks their dim light.
Why the moon?
So, the sun shines during the day, and the stars at night. The reasons for this are in the air layer surrounding the earth. But why is the moon sometimes visible, sometimes not? Yes, and when it is, it can take different types- from a thin crescent to a bright circle. What does it depend on?
It turns out that the moon itself does not glow. It works like a mirror that reflects the sun's rays to the ground. And observers can see only that part of the satellite that is illuminated. If we consider the whole cycle, then it begins with a very thin month, which resembles an inverted letter "C" or an arc from the letter "P". Within a week, it grows and becomes like a half circle. For the next week, it continues to increase and every day it approaches a full circle more and more. The next two weeks, the drawing decreases. And at the end of the month, the moon completely disappears from the night sky. More precisely, it is simply not visible, because only that part of it that turned away from the Earth is illuminated.
What do people see in space?
Astronauts in orbit are not interested in the question of why the sun shines during the day and the stars at night. And this is due to the fact that both are visible there at the same time. This fact is explained by the absence of air, which prevents the light from the stars from passing through the scattered rays of the sun. You can call them lucky, because they can immediately see the nearest star, and those that are far away.
By the way, night lights differ in color. And it is clearly visible even from the Earth. The main thing is to look closely. The hottest of them shine white and blue. Those stars that are colder than the previous ones are yellow. Our sun is one of them. And the coldest emit red light.
Continuation of the conversation about the stars
If the question of why the sun shines during the day and the stars at night arises in older children, then you can continue the conversation by remembering the constellations. They combine groups of stars that are in one place on celestial sphere. That is, they seem to us located nearby. In fact, there can be a huge distance between them. If we could fly far from solar system, they would not recognize the starry sky. Because the outlines of the constellations would change a lot.
In these groups of stars, the outlines of human figures, objects and animals were seen. In this regard, various names have appeared. Ursa Major and Minor, Orion, Cygnus, Southern Cross and many others. Today there are 88 constellations. Many of them are associated with myths and legends.
Because of the constellation, they change their position in the sky. And some are generally visible only in a certain season. There are constellations that cannot be seen in the Northern or Southern Hemisphere.
Over time, the constellations lost minor stars, and it became difficult to guess from their pattern how the name arose. The most famous constellation in the Northern Hemisphere - Ursa Major - has now turned into a "bucket". And modern children are tormented by the question: “Where is the bear here?”
