Line UMK B. A. Vorontsov-Velyaminov. Astronomy (11)

Astronomy

Natural science

How old is the Sun? Can the Sun cool down?

"What will happen if the Sun goes out?" – the question can be asked either in a scared voice or in a curious one. "How old is the Sun?" – is also one of the popular questions for children and adults.
In our new column “Why” we will regularly answer the most interesting ones!

Solar Passport

The Sun, the central body of the Solar System, is a typical representative of stars, the most common bodies in the Universe. The mass of the Sun is 2 * 10 to the 30th power kg. Like many other stars, the Sun is a huge ball that consists of hydrogen-helium plasma and is in equilibrium (more on that below).

How old is the Sun?

It is 4.6 billion years old. Quite a lot, right? Considering that life (arthropods - the ancestors of modern insects) appeared on our planet about 570 million years ago. The simplest organisms much earlier -about 3.5 billion years ago

Can the Sun go out?

There is no need to be afraid that the Sun will go out, because first it will flare up very, very strongly!
Inside the star (and any star that is in a state of equilibrium between pressure from inside and pressure from outside), at a certain moment a new stage of thermonuclear fusion flares up. Temperatures become so high - pressure increases so much that the outer shells of the star swell. The star will change irreversibly, turning into a red giant of enormous size. Our Sun will turn into the same giant.
Is the Sun Big?

The diameter of the Sun is almost 1,400,000 km. Many? Compare with the picture below! Millions of planets can fit inside the Sun, equal to Earth. 99.8% of the mass of the Solar System is concentrated in the Sun. And from 0.2% of everything else the planets are made (with 70% of the planetary mass coming from Jupiter). By the way, the Sun is constantly losing weight: it loses 4 million tons of its mass every second - they fly away in the form of radiation, every moment about 700 million tons of hydrogen turn into 696 tons of helium.

When and how will our Sun explode?

It would be more correct to say that it will turn into a red giant. IN at the moment The Sun is a yellow dwarf and simply burns hydrogen. Throughout its entire existence - 5.7 billion years, as we have already said - the Sun has been in a stable mode of hydrogen burning. And this fuel will last him for 5 billion years (more than the Earth has existed since the beginning of time!)

After the next stages of synthesis are turned on, the Sun will turn red, increase in size - up to the Earth's orbit (!) - and absorb our planet. And, yes, before that he will gobble up Venus and Mercury. But life on Earth will cease even before the Sun begins its transformation, because increasing luminosity and rising temperatures will lead to the fact that our oceans will evaporate a billion years before that.

How hot is the Sun?

The temperature on the surface of the Sun is approximately 6 thousand degrees Celsius. Inside the Sun, where thermonuclear reactions occur without stopping, the temperature is MUCH higher - it reaches 20 million degrees Celsius.

Is this what happens to all the stars? How then does life appear?

The sun is still a very small star, and therefore can work for a long time, steadily burning its hydrogen. Large stars, due to their enormous mass and the need to constantly resist gravitational compression (what is outside), use their powerful backpressure very quickly to waste their fuel. As a result, their cycle is completed not in billions, like the Sun, but in millions of years. Because of this, life on nearby planets does not have time to arise.
Advice to future astronauts: if you are looking for life on planets in other systems, do not choose massive stars, but rather immediately focus on a star of the solar class (Class G - surface temperature 5000–6000 degrees. Color yellow).

The textbook by B. A. Vorontsov-Velyaminov, E. K. Strout meets the requirements of the Federal State Educational Standard and is intended for the study of astronomy on basic level. It retains the classical structure of presentation educational material, much attention is paid current state science. Over the past decades, astronomy has made enormous strides. Today it is one of the fastest growing areas of natural science. New established research data celestial bodies from spacecraft and modern large ground-based and space telescopes have found their place in the textbook.

It is assumed that the age of the Sun is at least equal to the age of the Earth. The significantly larger source of solar radiation energy is nuclear rather than gravitational energy.  

The geological age of the Earth is approaching five billion years; This is or is slightly greater than the age of the Sun, and the oldest stars in the Galaxy are more than 10 billion years old. The history of the Universe as a whole is 15 - 18 billion years, and before the formation modern planets, stars and galaxies, all its matter was, apparently, an almost homogeneous medium. The knowledge accumulated over many decades about the structure and evolution of celestial bodies, the observational discoveries of the last half century, and especially the discovery of the expansion of the Universe and the existence of isotropic cosmic microwave background radiation in it, now allow us to form a certain idea about the properties of the cosmic environment in the prestellar, pre-galactic era, about physical processes, which led to the formation of the observable structures of the Universe from homogeneous matter. This is the content of modern cosmogony.  

Thomson put forward a hypothesis according to which the radiation of the Sun is supported by gravitational energy released during its compression. Estimate the age of the Sun / using this hypothesis, assuming that in the initial state the matter of the Sun was uniformly distributed throughout the entire infinite space, and in the final state the density of the solar matter is the same throughout the entire volume of the Sun.  

We do not know the evolutionary age of the Sun with sufficient certainty, since we do not know the helium content in it. It is believed that the evolutionary age of the Sun lies somewhere in the region considered.  

The value (1.2.33) agrees well with data on the ages of stars and galaxies (12 billion years), obtained on the basis of completely different considerations. It is also consistent with the geological age of the Earth (4 - 5 billion years), which serves as a lower limit for the age of the Sun.  

The fuel that generates solar heat is thus hydrogen, and the product of its combustion is helium. It can be easily calculated that, with a constant release of energy, the hydrogen in the Sun will last for approximately 1011 years. The age of the Sun should be taken to be approximately 5 billion years. Consequently, only about one-twentieth of the original fuel supply has been consumed.  

Solid lines show data for dust particles consisting of refractory substances, dashed lines - for dust particles consisting of volatile substances. For comparison, the arrows indicate the age of the Sun (right arrow) and the rotation period of the Galaxy at a distance corresponding to the distance of the Sun from the galactic center.  

The energy released in this case turned out to be too great, and therefore after some time an explosion occurred in the form of a Supernova, during which the nuclei of the heaviest elements were formed; the mass of the star decreased due to the ejection of matter. This entire process could be repeated repeatedly until the mass of the central massive star fell below a critical limit. Such a system should have a lifetime of about 5 billion years, which corresponds to the age of the Sun and provides a time interval sufficient for chemical, geological and biological evolution to reach modern levels.  

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Humanity cannot imagine life without the brightest luminary visible to us. Why, “can’t imagine life”? Without sunlight, our planet would undoubtedly be simply uninhabited. Indeed, to this day our star is the main source of energy on Earth.

It was possible to more or less accurately determine how old the Sun is relatively recently, with the advent of super-powerful computers. No one can reliably indicate the age of the star, but based on computer modeling data, the star itself is approximately four and a half billion years old. Astrophysicists believe that this is not at all an advanced age for a cosmic body. It is believed that stars similar to our Sun in type and mass have life cycle ten billion years, and if so, then the center of our planetary system is at the peak of its development, almost exactly in the middle.

The further fate of the Sun

Of course, there is no point for us to look that far, but, nevertheless, it is interesting what will happen when the life cycle of the Sun comes to an end. Meticulous astronomers and astrophysicists have certain considerations in this regard.

In our time, the conversion of hydrogen into helium through thermonuclear reactions is actively taking place in the core of the star. Every second approximately 4 million tons different substances in the process of these physical and chemical cataclysms, it turns into radiant energy, which, in fact, “feeds” all nearby planets, including our Earth.

The processes of thermonuclear reactions occur in such a way that as the amount of hydrogen decreases, the temperature of the Sun increases all the time and it shines brighter and brighter. This is, of course, invisible to us, but scientists say that in about a billion years, a star called the Sun will burn more than 10 times brighter. Accordingly, the temperature on Earth will also rise. Some scientists claim that within a billion years earthly life will cease completely, except perhaps in ocean depths and under polar ice. Finally, all forms of life on Earth will disappear in about 8 billion years - the Sun will become brighter at 40C on the surface of our planet, water will completely evaporate and the existence of living matter will become impossible. The Earth will turn into a semblance of the current Venus, and in another couple of billion years it will be completely absorbed by the Sun, which will “inflate” 256 times.

This is such sad news. We can only hope that in a billion years the level of our civilization will reach such heights that humanity will be able to cope with this scourge.

The closest star to us is, of course, the Sun. The distance from the Earth to it is quite small in cosmic parameters: from the Sun to the Earth sunlight It only takes 8 minutes.

The Sun is not an ordinary yellow dwarf, as previously thought. This is the central body of the solar system, around which the planets revolve, with a large number heavy elements. This is a star formed after several supernova explosions, around which a planetary system was formed. Due to the location close to ideal conditions, life arose on the third planet Earth. The Sun is already five billion years old. But let's figure out why it shines? What is the structure of the Sun and what are its characteristics? What does the future hold for him? How significant an impact does it have on the Earth and its inhabitants? The Sun is a star around which all 9 planets of the solar system, including ours, revolve. 1 a.u. (astronomical unit) = 150 million km - the same is the average distance from the Earth to the Sun. The solar system contains nine major planets, about a hundred satellites, many comets, tens of thousands of asteroids (minor planets), meteoroids and interplanetary gas and dust. At the center of it all is our Sun.

The sun has been shining for millions of years, which is confirmed by modern biological research obtained from the remains of blue-green-blue algae. If the temperature of the surface of the Sun changed by even 10%, all life on Earth would die. Therefore, it is good that our star evenly radiates the energy necessary for the prosperity of humanity and other creatures on Earth. In the religions and myths of the peoples of the world, the Sun has always occupied the main place. For almost all peoples of antiquity, the Sun was the most important deity: Helios - among the ancient Greeks, Ra - the sun god of the ancient Egyptians and Yarilo among the Slavs. The sun brought warmth, harvest, everyone revered it, because without it there would be no life on Earth. The size of the Sun is impressive. For example, the mass of the Sun is 330,000 times the mass of the Earth, and its radius is 109 times greater. But the density of our star is small - 1.4 times greater than the density of water. The movement of spots on the surface was noticed by Galileo Galilei himself, thus proving that the Sun does not stand still, but rotates.

Convective zone of the Sun

The radioactive zone is about 2/3 of the internal diameter of the Sun, and the radius is about 140 thousand km. Moving away from the center, photons lose their energy under the influence of collision. This phenomenon is called the phenomenon of convection. This is reminiscent of the process that occurs in a boiling kettle: energy coming from heating element, much more than the amount that is removed by conduction. Hot water, located close to the fire, rises, and the colder one goes down. This process is called convention. The meaning of convection is that denser gas is distributed over the surface, cools and again goes to the center. The mixing process in the convective zone of the Sun is carried out continuously. Looking through a telescope at the surface of the Sun, you can see its granular structure - granulations. It feels like it's made of granules! This is due to convection occurring beneath the photosphere.

Photosphere of the Sun

A thin layer (400 km) - the photosphere of the Sun, is located directly behind the convective zone and represents the “real solar surface” visible from Earth. Granules in the photosphere were first photographed by the Frenchman Janssen in 1885. The average granule has a size of 1000 km, moves at a speed of 1 km/sec and exists for approximately 15 minutes. Dark formations in the photosphere can be observed in the equatorial part, and then they shift. Strong magnetic fields are a distinctive feature of such spots. A dark color is obtained due to the lower temperature relative to the surrounding photosphere.

Chromosphere of the Sun

Chromosphere of the Sun (colored sphere) – dense layer (10,000 km) solar atmosphere, which is located just beyond the photosphere. The chromosphere is quite problematic to observe due to its close location to the photosphere. It is best seen when the Moon covers the photosphere, i.e. during solar eclipses.

Solar prominences are huge emissions of hydrogen, resembling long luminous filaments. The prominences rise to enormous distances, reaching the diameter of the Sun (1.4 mm km), move at a speed of about 300 km/sec, and the temperature reaches 10,000 degrees.

The solar corona is the outer and extended layers of the Sun's atmosphere, originating above the chromosphere. The length of the solar corona is very long and reaches values ​​of several solar diameters. Scientists have not yet received a clear answer to the question of where exactly it ends.

The composition of the solar corona is a rarefied, highly ionized plasma. It contains heavy ions, electrons with a helium core and protons. The temperature of the corona reaches from 1 to 2 million degrees K, relative to the surface of the Sun.

The solar wind is a continuous outflow of matter (plasma) from the outer shell of the solar atmosphere. It consists of protons, atomic nuclei and electrons. The speed of the solar wind can vary from 300 km/sec to 1500 km/sec, in accordance with the processes occurring on the Sun. The solar wind spreads throughout solar system and, interacting with magnetic field Earth, calls various phenomena, one of which is the northern lights.

Characteristics of the Sun

Mass of the Sun: 2∙1030 kg (332,946 Earth masses)
Diameter: 1,392,000 km
Radius: 696,000 km
Average density: 1,400 kg/m3
Axis tilt: 7.25° (relative to the ecliptic plane)
Surface temperature: 5,780 K
Temperature at the center of the Sun: 15 million degrees
Spectral class: G2 V
Average distance from Earth: 150 million km
Age: 5 billion years
Rotation period: 25.380 days
Luminosity: 3.86∙1026 W
Apparent magnitude: 26.75m