Units
Most stellar characteristics are typically expressed in SI, but GHS is also used (for example, luminosity is expressed in ergs per second). Mass, luminosity and radius are usually given in relation to our Sun:
To indicate the distance to stars, units such as light year and parsec are used.
Large distances such as the radius of giant stars or the semimajor axis of binary star systems are often expressed using an astronomical unit (AU) - the average distance between the Earth and the Sun (150 million km).
physical characteristics
The masses of the vast majority of modern stars range from 0.071 solar masses (75 Jupiter masses) to 100-150 solar masses; perhaps the first stars were even more massive. The temperature in the depths of stars reaches 10-12 million.
Distance
There are many ways to determine the distance to a star. But the most accurate and the basis for all other methods is the method of measuring the parallaxes of stars. The first to measure the distance to the star Vega was the Russian astronomer Vasily Yakovlevich Struve in 1837. Determining parallaxes from the Earth's surface makes it possible to measure distances up to 100 parsecs, and from special astrometric satellites, such as Hipparcos, up to 1000 pc. If the star is part of a star cluster, then we will not be much mistaken if we take the distance to the star equal to the distance to the cluster. If the star belongs to the Cepheid class, then the distance can be found from the relationship between the pulsation period and the absolute magnitude. Basically, photometry is used to determine the distance to distant stars.
Weight
The mass of a star can only be reliably determined if it is a component of a binary star. In this case, the mass can be calculated using Kepler's generalized third law. But even so, the error estimate ranges from 20% to 60% and, to a large extent, depends on the error in determining the distance to the star. In all other cases, it is necessary to determine the mass by indirect signs, for example, the dependence of the luminosity and mass of the star. .
Chemical composition
An extremely important characteristic is its chemical composition, both from the point of view of the star and from the point of view of the observer. And although the proportion of elements heavier than helium is no more than a few percent, they play an important role in the life of a star. Thanks to them, nuclear reactions can slow down or speed up, and this will affect the brightness of the star, its color, and life expectancy. So the greater the metallicity of a massive star, the smaller the supernova remnant will be. An observer, knowing the chemical composition of a star, can fairly confidently predict the time of star formation. Since all those tragic changes that occur with a star throughout its life do not touch the surface of the star. This is always so few massive and moderately massive stars, and almost always for massive stars.
Structure of stars
The emergence and evolution of stars
A star begins its life as a cold, tenuous cloud of interstellar gas, compressed by its own gravity. During compression, gravitational energy turns into heat, and the temperature of the gas globule increases. When the temperature in the core reaches several million Kelvin, thermonuclear reactions begin and compression stops. The star remains in this state for most of its life, being on the main sequence of the Hertzsprung-Russell diagram, until the fuel reserves in its core run out. When all the hydrogen in the center of the star turns into helium, thermonuclear burning of hydrogen continues at the periphery of the helium core.
During this period, the structure of the star begins to change noticeably. Its luminosity increases, the outer layers expand, and the inner layers, on the contrary, contract. And for the time being, the brightness of the star also decreases. The surface temperature decreases - the star becomes a red giant. A star spends significantly less time on the giant branch than on the main sequence. When the mass of its isothermal helium core becomes significant, it cannot withstand its own weight and begins to shrink; the increasing temperature stimulates the thermonuclear transformation of helium into heavier elements.
The vast majority of stars, including the Sun, end their evolution by contracting until the pressure of degenerate electrons balances gravity. In this state, when the size of the star decreases by a hundred times, and the density becomes a million times higher than the density of water, the star is called a white dwarf. It is deprived of energy sources and, gradually cooling down, becomes dark and invisible.
In stars more massive than the Sun, the pressure of degenerate electrons cannot contain the compression of the core, and it continues until most of the particles turn into neutrons, packed so tightly that the size of the star is measured in kilometers, and its density is 280 trillion. times the density of water. Such an object is called a neutron star; its equilibrium is maintained by the pressure of the degenerate neutron matter.
Scheme of the evolution of single stars
|
small masses 0.08M sun |
moderate masses |
massive stars |
||
0.5M sun | 3M sun | 8M sun | M * >10M sun |
| |
|
burning of hydrogen in the core |
||||
| helium white dwarfs |
degenerate Not the core |
non-degenerate Not the core |
||
| helium flash | ||||
|
quiet combustion of helium in the core |
||||
|
CO white dwarf |
degenerate CO core | non-degenerate CO core | ||
|
carbon det. |
combustion of carbon in the core. CO to Fe | |||
|
combustion of carbon in the core. C to O, Ne, Si, Fe, Ni.. |
||||
|
O,Ne,Mg... white dwarf or neutron star |
black hole |
|||
Scheme of the evolution of single stars. According to V. A. Baturin and I. V. Mironova
Duration of stellar evolution
Classification of stars
Stars are classified by luminosity, mass, surface temperature, chemical composition, spectral features (spectral class) and multiplicity.
Multiple stars
Stellar systems can be single and multiple: double, triple and higher multiplicity. If a system includes more than ten stars, it is usually called a star cluster. Double (multiple) stars are very common. According to some estimates, more than 70% of the stars in the galaxy are multiples. So, among the 32 stars closest to Earth, 12 are multiple, of which 10 are double, including the brightest visually observable star, Sirius. In the vicinity of 20 parsecs from the Solar System there are more than 3000 stars, about half are double stars of all types
Star designations
In the beautifully illustrated Uranometry (Uranometria,) by the German astronomer I. Bayer ( -), which depicts the constellations and the legendary figures associated with their names, the stars were first designated by letters of the Greek alphabet approximately in descending order of their brightness: α - the brightest star of the constellation, β - second in brilliance, etc. When there were not enough letters of the Greek alphabet, Bayer used Latin. The full designation of the star consisted of the mentioned letter and the Latin name of the constellation. For example, Sirius is the brightest star in the constellation Canis Major, so it is designated as α Canis Majoris, or α CMa for short; Algol, the second brightest star in Perseus, is designated β Persei, or β Per. Bayer, however, did not always follow the rule he introduced, and there are a large number of exceptions to Bayer's notation.
Thermonuclear fusion reactions in the interior of stars
Thermonuclear fusion reactions of elements are the main source of energy for most stars.
The most famous stars
| № | designation | Name |
facts about stars in space
The light of the stars, before we see it, passes through the thickness of the layers of the atmosphere (air), which refract the light of the star and give us a different picture, which we observe when admiring the stars. The stars twinkle and shine beautifully. When in fact the light from the star always comes out smoothly, with a constant direct glow.
facts about stars in space
Astronomers have recorded a large number of double stars in space. This is the name given to stars that are close to each other - one large star, with its large field of attraction, attracts the smallest star to itself, and it seems that the stars are as if glued to each other. But this is just what it looks like, but in fact, if the stars come together closely, a powerful nuclear explosion will occur from the collision, the stars will simply explode. But that never happens. Some reason and force forces the stars to keep a certain distance.
But, a couple more stars can join such a double conjunction - a new shining star can be born from the energy emitted by these bodies. True, this event happens extremely rarely in the stellar world.
facts about stars in space
Our Sun will also become such a dwarf in the future. But what will happen is not at all soon, in about a hundred million years. The Sun will first become huge, as if inflated like a balloon, turning into a large one, and then will sharply decrease in size, approximately to the size of the Earth or the Moon, and will go out, turning into a “white dwarf”.
As you know, a heated metal first begins to glow red, then yellow and finally white as the temperature increases. Same with the stars. Reds are the coldest, and whites (or even blues!) are the hottest.
A newly flared star will have a color corresponding to the energy released in its core, and the intensity of this release, in turn, depends on the mass of the star. This means that the colder the stars, the redder they are.
Heavy stars are white and hot, while light, less massive stars are red and cool.
When we look at the farthest star, we are looking 4 billion years into the past. The light from it, traveling at a speed of almost 300,000 km/second, reaches us only after many years.
Black holes are the opposite of white dwarfs. They appear from stars that are too large, unlike dwarfs, which are born from stars that are too small. The golden mean between white dwarfs and black holes is the so-called neutron stars. They emit very large amounts of light due to the enormous gravitational force around them.
Neutron stars are the most powerful magnets in the Universe. The magnetic field of a neutron star is a million million times greater than the Earth's magnetic field.
facts about stars in space
The largest star discovered by scientists to date is 100 times the mass of the Sun.
Astronomers believe that the maximum mass for a star is 120 solar masses; it cannot be larger in the entire Universe.
Pistol is the hottest star that doesn't cool at all. It is unknown how it manages to withstand such high temperatures without exploding. By the way, this star creates a specific “solar wind”, similar to our Northern Lights.
A car traveling at 96 kilometers per hour would take 48 million years to reach our closest star (after the Sun), Proxima Centauri.
Every year at least forty new stars are born in our galaxy.
Video: Biggest Stars Comparisons
facts about stars in space
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> Stars
Stars– massive gas balls: history of observations, names in the Universe, classification with photos, birth of a star, development, double stars, list of the brightest.
Stars- celestial bodies and giant glowing spheres of plasma. There are billions of them in our Milky Way galaxy alone, including the Sun. Not long ago we learned that some of them also have planets.
History of stargazing
Now you can easily buy a telescope and observe the night sky or use telescopes online on our website. Since ancient times, the stars in the sky have played an important role in many cultures. They were noted not only in myths and religious stories, but also served as the first navigational tools. That is why astronomy is considered one of the oldest sciences. The advent of telescopes and the discovery of the laws of motion and gravity in the 17th century helped to understand that all stars resemble ours, and therefore obey the same physical laws.
The invention of photography and spectroscopy in the 19th century (the study of the wavelengths of light emitted by objects) provided insights into stellar composition and principles of motion (the creation of astrophysics). The first radio telescope appeared in 1937. With its help it was possible to find invisible stellar radiation. And in 1990, it was possible to launch the first Hubble space telescope, capable of obtaining the deepest and most detailed view of the Universe (high-quality Hubble photos for various celestial bodies can be found on our website).
Name of the stars of the Universe
Ancient people did not have our technical advantages, so they recognized images of various creatures in celestial objects. These were the constellations about which myths were composed in order to remember the names. Moreover, almost all of these names have been preserved and are used today.
In the modern world there are (among them 12 belong to the zodiac). The brightest star is designated "alpha", the second is designated "beta", and the third is designated "gamma". And so it continues until the end of the Greek alphabet. There are stars that represent body parts. For example, the brightest star of Orion (Alpha Orionis) is “the arm (armpit) of a giant.”
Do not forget that all this time many catalogs were compiled, whose designations are still used today. For example, the Henry Draper Catalog offers spectral classifications and positions for 272,150 stars. Betelgeuse's designation is HD 39801.
But there are incredibly many stars in the sky, so for new ones they use abbreviations denoting the star type or catalogue. For example, PSR J1302-6350 is a pulsar (PSR), J uses the J2000 coordinate system, and the last two groups of numbers are coordinates with latitude and longitude codes.
Are all stars the same? Well, when you observe without using technology, they only differ slightly in brightness. But these are just huge balls of gas, right? Not really. In fact, stars have a classification based on their main characteristics.
Among the representatives you can find blue giants and tiny brown dwarfs. Sometimes you come across weird stars, like neutron stars. Diving into the Universe is impossible without understanding these things, so let's take a closer look at the star types.
 Most of the universe's stars are in the main sequence stage. You can remember the Sun, Alpha Centauri A and Sirus. They can differ radically in scale, massiveness and brightness, but they perform the same process: they transform hydrogen into helium. This produces a huge energy surge. Such a star experiences a sensation of hydrostatic balance. Gravity causes the object to shrink, but nuclear fusion pushes it out. These forces work in balance, and the star manages to maintain its spherical shape. The size depends on the massiveness. The line is 80 Jupiter masses. This is the minimum mark at which it is possible to activate the melting process. But in theory, the maximum mass is 100 solar. |
 If there is no fuel, then the star no longer has enough mass to prolong nuclear fusion. It turns into a white dwarf. External pressure does not work, and it shrinks in size due to gravity. The dwarf continues to shine because hot temperatures still remain. When it cools down, it will reach the background temperature. This will take hundreds of billions of years, so for now it is simply impossible to find a single representative.
|
 Cepheids are stars that have undergone evolution from the main sequence to the Cepheid instability strip. These are ordinary radio-pulsating stars with a noticeable relationship between periodicity and luminosity. Scientists value them for this, because they are excellent assistants in determining distances in space. They also show variations in radial velocity consistent with the photometric curves. The brighter ones exhibit a long periodicity. Classic representatives are supergiants, whose mass is 2-3 times that of the Sun. They are in the process of burning fuel during the main sequence stage and transform into red giants, crossing the Cepheid instability line. |
 To be more precise, the concept of “double star” does not reflect the real picture. In fact, before us is a star system represented by two stars revolving around a common center of mass. Many people make the mistake of mistaking two objects that appear close to each other when observed with the naked eye for a double star. Scientists benefit from these objects because they help calculate the mass of individual participants. As they move in a common orbit, Newton's calculations for gravity allow the mass to be calculated with incredible accuracy. Several categories can be distinguished according to visual properties: occulting, visual binary, spectroscopic binary and astrometric. Eclipsing stars are stars whose orbits create a horizontal line from the point of observation. That is, a person sees a double eclipse on one plane (Algol). Visual - two stars that can be resolved using a telescope. If one of them shines very brightly, it can be difficult to separate the second. |
Star formation
Let's take a closer look at the process of star birth. First we see a giant, slowly rotating cloud filled with hydrogen and helium. Internal gravity causes it to curl inward, causing it to spin faster. The outer parts are transformed into a disk, and the inner parts into a spherical cluster. The material breaks down, becoming hotter and denser. Soon a spherical protostar appears. When heat and pressure rise to 1 million °C, atomic nuclei fuse and a new star ignites. Nuclear fusion converts a small amount of atomic mass into energy (1 gram of mass converted into energy is equivalent to the explosion of 22,000 tons of TNT). Also watch the explanation in the video to better understand the issue of stellar birth and development.
Evolution of protostellar clouds
Astronomer Dmitry Vibe about actualism, molecular clouds and the birth of a star:
The Birth of Stars
Astronomer Dmitry Vibe about protostars, the discovery of spectroscopy and the gravoturbulent model of star formation:
Flares on young stars
Astronomer Dmitry Vibe about supernovae, types of young stars and an outbreak in the constellation Orion:
Stellar evolution
Based on the mass of a star, its entire evolutionary path can be determined, as it passes through certain patterned stages. There are stars of intermediate mass (like the Sun) 1.5-8 times the solar mass, more than 8, and also up to half the solar mass. Interestingly, the greater the mass of a star, the shorter its lifespan. If it reaches less than a tenth of the Sun, then such objects fall into the category of brown dwarfs (they cannot ignite nuclear fusion).
An intermediate-mass object begins life as a cloud 100,000 light years across. To collapse into a protostar, the temperature must be 3725°C. Once hydrogen fusion begins, T Tauri, a variable with fluctuations in brightness, can be formed. The subsequent destruction process will take 10 million years. Further, its expansion will be balanced by the compression of gravity, and it will appear as a main sequence star, receiving energy from hydrogen fusion in the core. The bottom figure demonstrates all the stages and transformations in the process of stellar evolution.
Once all the hydrogen has melted into helium, gravity will crush the matter into the core, setting off a rapid heating process. The outer layers expand and cool, and the star becomes a red giant. Next, helium begins to fuse. When it dries up, the core contracts and becomes hotter, expanding the shell. At maximum temperature, the outer layers are blown away, leaving a white dwarf (carbon and oxygen) whose temperature reaches 100,000 °C. There is no more fuel, so cooling occurs gradually. After billions of years, they end their lives as black dwarfs.
The formation and death processes of a high-mass star occur incredibly quickly. It only takes 10,000-100,000 years for it to move from a protostar. During the main sequence, these are hot and blue objects (1000 to a million times brighter than the Sun and 10 times wider). Next we see a red supergiant beginning to fuse carbon into heavier elements (10,000 years). As a result, an iron core with a width of 6000 km is formed, whose nuclear radiation can no longer resist the force of gravity.
As the star approaches 1.4 solar masses, electron pressure can no longer keep the core from collapsing. Because of this, a supernova is formed. When destroyed, the temperature rises to 10 billion °C, breaking the iron into neutrons and neutrinos. In just a second, the core collapses to a width of 10 km and then explodes in a Type II supernova.
If the remaining core reaches less than 3 solar masses, it turns into a neutron star (practically from only neutrons). If it rotates and emits radio pulses, then it is . If the core is more than 3 solar masses, then nothing will stop it from destruction and transformation into .
A low-mass star burns through its fuel reserves so slowly that it will take 100 billion to 1 trillion years to become a main sequence star. But the age of the Universe reaches 13.7 billion years, which means such stars have not yet died. Scientists have found that these red dwarfs are not destined to merge with anything other than hydrogen, which means they will never grow into red giants. As a result, their fate is cooling and transformation into black dwarfs.
Thermonuclear reactions and compact objects
Astrophysicist Valery Suleymanov on atmospheric modeling, the “big debate” in astronomy and the merger of neutron stars:
Astrophysicist Sergei Popov on the distance to stars, the formation of black holes and Olbers’ paradox:
We are accustomed to our system being illuminated exclusively by one star. But there are other systems in which two stars in the sky orbit relative to each other. More precisely, only 1/3 of the stars similar to the Sun are located alone, and 2/3 are double stars. For example, Proxima Centauri is part of a multiple system that includes Alpha Centauri A and B. About 30% of stars are multiples.
This type is formed when two protostars develop side by side. One of them will be stronger and will begin to influence gravity, creating mass transfer. If one appears as a giant, and the second as a neutron star or black hole, then we can expect the appearance of an X-ray binary system, where the matter will heat up incredibly strongly - 555500 ° C. In the presence of a white dwarf, gas from the companion can flare up as a nova. Periodically, the dwarf's gas accumulates and can instantly merge, causing the star to explode in a Type I supernova, capable of eclipsing the galaxy with its brilliance for several months.
Relativistic double stars
Astrophysicist Sergei Popov on measuring the mass of a star, black holes and ultra-powerful sources:
Properties of double stars
Astrophysicist Sergei Popov on planetary nebulae, white helium dwarfs and gravitational waves:
Characteristics of stars
Brightness
Magnitude and luminosity are used to describe the brightness of stellar celestial bodies. The concept of magnitude dates back to the work of Hipparchus in 125 BC. He numbered star groups based on apparent brightness. The brightest ones are the first magnitude, and so on up to the sixth. However, the distance between and a star can affect visible light, so now they are adding a description of the actual brightness - the absolute value. It is calculated using its apparent magnitude as if it were 32.6 light years from Earth. The modern magnitude scale rises above six and falls below one (apparent magnitude reaches -1.46). Below you can study the list of the brightest stars in the sky from the perspective of an Earth observer.
List of the brightest stars visible from Earth
| № | Name | Distance, St. years | Apparent value | Absolute value | Spectral class | Celestial hemisphere |
|---|---|---|---|---|---|---|
| 0 | 0,0000158 | −26,72 | 4,8 | G2V | ||
| 1 | 8,6 | −1,46 | 1,4 | A1Vm | South | |
| 2 | 310 | −0,72 | −5,53 | A9II | South | |
| 3 | 4,3 | −0,27 | 4,06 | G2V+K1V | South | |
| 4 | 34 | −0,04 | −0,3 | K1.5IIIp | Northern | |
| 5 | 25 | 0.03 (variable) | 0,6 | A0Va | Northern | |
| 6 | 41 | 0,08 | −0,5 | G6III + G2III | Northern | |
| 7 | ~870 | 0.12 (variable) | −7 | B8Iae | South | |
| 8 | 11,4 | 0,38 | 2,6 | F5IV-V | Northern | |
| 9 | 69 | 0,46 | −1,3 | B3Vnp | South | |
| 10 | ~530 | 0.50 (variable) | −5,14 | M2Iab | Northern | |
| 11 | ~400 | 0.61 (variable) | −4,4 | B1III | South | |
| 12 | 16 | 0,77 | 2,3 | A7Vn | Northern | |
| 13 | ~330 | 0,79 | −4,6 | B0.5Iv + B1Vn | South | |
| 14 | 60 | 0.85 (variable) | −0,3 | K5III | Northern | |
| 15 | ~610 | 0.96 (variable) | −5,2 | M1.5Iab | South | |
| 16 | 250 | 0.98 (variable) | −3,2 | B1V | South | |
| 17 | 40 | 1,14 | 0,7 | K0IIIb | Northern | |
| 18 | 22 | 1,16 | 2,0 | A3Va | South | |
| 19 | ~290 | 1.25 (variable) | −4,7 | B0.5III | South | |
| 20 | ~1550 | 1,25 | −7,2 | A2Ia | Northern | |
| 21 | 69 | 1,35 | −0,3 | B7Vn | Northern | |
| 22 | ~400 | 1,50 | −4,8 | B2II | South | |
| 23 | 49 | 1,57 | 0,5 | A1V + A2V | Northern | |
| 24 | 120 | 1.63 (variable) | −1,2 | M3.5III | South | |
| 25 | 330 | 1.63 (variable) | −3,5 | B1.5IV | South |
Other famous stars:
The luminosity of a star is the rate at which energy is emitted. It is measured by comparison with solar brightness. For example, Alpha Centauri A is 1.3 times brighter than the Sun. To make the same calculations in absolute magnitude, you will have to take into account that 5 on the absolute scale is equivalent to 100 at the luminosity mark. Brightness depends on temperature and size.
Color
You may have noticed that stars vary in color, which actually depends on the surface temperature.
| Class | Temperature,K | true color | Visible color | Main features |
|---|---|---|---|---|
| O | 30 000-60 000 | blue | blue | Weak lines of neutral hydrogen, helium, ionized helium, multiply ionized Si, C, N. |
| B | 10 000-30 000 | white-blue | white-blue and white | Absorption lines of helium and hydrogen. Weak H and K lines of Ca II. |
| A | 7500-10 000 | white | white | Strong Balmer series, lines H and K of Ca II intensify towards class F. Also, closer to class F, lines of metals begin to appear |
| F | 6000-7500 | yellow-white | white | The H and K lines of Ca II, the lines of metals, are strong. The hydrogen lines begin to weaken. The Ca I line appears. The G band formed by the Fe, Ca and Ti lines appears and intensifies. |
| G | 5000-6000 | yellow | yellow | The H and K lines of Ca II are intense. Ca I line and numerous metal lines. The hydrogen lines continue to weaken, and bands of CH and CN molecules appear. |
| K | 3500-5000 | orange | yellowish orange | Metal lines and G band are intense. The hydrogen line is almost invisible. TiO absorption bands appear. |
| M | 2000-3500 | red | orange-red | The bands of TiO and other molecules are intense. The G band is weakening. Metal lines are still visible. |
Each star has one color but produces a wide spectrum, including all types of radiation. A variety of elements and compounds absorb and emit colors or wavelengths of color. By studying the stellar spectrum, you can understand the composition.
Surface temperature
The temperature of stellar celestial bodies is measured in Kelvin with a zero temperature of -273.15 °C. The temperature of a dark red star is 2500K, a bright red one is 3500K, a yellow star is 5500K, and a blue star is from 10,000K to 50,000K. Temperature is influenced in part by mass, brightness, and color.
Size
The size of stellar space objects is determined in comparison with the solar radius. Alpha Centauri A has 1.05 solar radii. Sizes may vary. For example, neutron stars extend 20 km in width, but supergiants are 1000 times the solar diameter. Size affects stellar brightness (luminosity is proportional to the square of the radius). In the lower figures you can see a comparison of the sizes of stars in the Universe, including a comparison with the parameters of the planets of the Solar system.
Comparative sizes of stars
Weight
Here, too, everything is calculated in comparison with solar parameters. The mass of Alpha Centauri A is 1.08 solar. Stars with the same masses may not converge in size. The mass of a star affects its temperature.
Since ancient times, man has sought to comprehend the unknown, fixing his gaze on the night sky, on which millions of stars are literally scattered. Scientists have always paid serious attention to the study of space and now they have the opportunity, with the help of powerful scientific equipment, not only to examine it, but also to take unique photographs. I invite you to enjoy the amazing photographs of space that they took quite recently and learn some interesting facts.
The beautiful triple nebula NGC 6514 in the constellation Sagittarius. The nebula's name was suggested by William Herschel and means "divided into three petals." The exact distance to it is unknown, but according to various estimates it ranges from 2 to 9 thousand light years. NGC 6514 consists of three main types of nebulae - emission (pinkish), reflective (blue) and absorption (black). (Photo by Máximo Ruiz):
Space Elephant Trunk
The Elephant Trunk Nebula meanders around an emission nebula and a young star cluster in the IC 1396 complex in the constellation Cepheus. The length of the cosmic elephant trunk is more than 20 light years. These dark, whisker-like clouds contain material for the formation of new stars and hide protostars - stars in the final stages of their formation - behind layers of cosmic dust. (Photo by Juan Lozano de Haro):
Ringworld
Hoag's Object is a strange ring-shaped galaxy in the constellation Serpens, named after its discoverer. The distance to Earth is about 600 million light years. In the center of the galaxy there is a cluster of relatively old yellow stars. It is surrounded by an almost regular ring of younger stars with a blue tint. The diameter of the galaxy is about 100 thousand light years. Among the hypotheses about the origin, a collision of galaxies that occurred several billion years ago is being considered. (Photo by R. Lucas (STScI | AURA), Hubble Heritage Team, NASA):
Moon over Andromeda
The large spiral galaxy, the Andromeda Nebula, is located just 2.5 million light years away and is the closest spiral galaxy to our Milky Way. It can be seen with the naked eye as a small blurry speck in the sky. This composite photograph compares the angular size of the Andromeda Nebula and the Moon. (Photo by Adam Block and Tim Puckett):
Io's ever-changing surface
Jupiter's moon Io is the most volcanically active object in the solar system. Its surface is constantly changing due to new lava flows. This photograph of the side of Io's moon facing Jupiter is a composite of images taken in 1996 by NASA's Galileo spacecraft. The absence of impact craters is explained by the fact that the entire surface of Io is covered with a layer of volcanic deposits much faster than craters appear. The likely cause of the volcanic activity is the changing gravitational tides caused by the huge Jupiter. (Photo by Galileo Project, JPL, NASA):
Cone Nebula
Strange formations can be observed near the Cone Nebula. They arise from the interaction of interstellar dust with light and gas emanating from young stars. The blue glow around the star S Mon is the reflection of the bright star's radiation from surrounding stardust. The star S Mon is located in the open star cluster NGC 2264, located 2,500 light-years from Earth. (Photo by Subaru Telescope (NAOJ) & DSS):
Spiral galaxy NGC 3370
Spiral galaxy NGC 3370 is located about 100 million light-years away in the constellation Leo. It is similar in size and structure to our Milky Way. (Photo by NASA, ESA, Hubble Heritage (STScI | AURA):
Spiral Galaxy M74
This spiral galaxy is one of the photogenic ones. It consists of approximately 100 billion stars and is located at a distance of about 32 million light years from us. Presumably, this galaxy contains a black hole of intermediate mass (that is, significantly larger than stellar masses, but smaller than the black holes at the center of galaxies). (Photo by NASA, ESA, and the Hubble Heritage (STScI | AURA) - ESA | Hubble Collaboration):
Lagoon Nebula
This is a giant interstellar cloud and H II region in the constellation Sagittarius. At a distance of 5,200 light-years, the Lagoon Nebula is one of two star-forming nebulae faintly visible to the naked eye in the mid-latitudes of the Northern Hemisphere. Not far from the center of the Lagoon is a bright hourglass region - the result of the turbulent interaction of stellar winds and powerful radiation. (Photo by Ignacio Diaz Bobillo):
Luminous streak in the Pelican Nebula
Easily visible in the sky, the luminous streak of IC 5067 is part of the large Pelican emission nebula with a characteristic shape. The stripe is about 10 light years long and outlines the head and neck of the space pelican. It is located at a distance of about 2,000 light years from us. (Photo by César Blanco González):
thunder cloud
This beautiful photo was taken in southern Alberta, Canada. This is a receding rain cloud, with unusual protrusions characteristic of squamous clouds visible on its near edge, and rain falling from the far edge of the cloud. Also read the article “Rare types of clouds”. (Photo by Alan Dyer):
Three bright nebulae in Sagittarius
The Lagoon Nebula M8 is to the left of the center of the picture, M20 is a colored nebula to the right. The third nebula, NGC 6559, lies just above M8 and is separated from it by a dark streak of stardust. All of them are located at a distance of about 5 thousand light years from us. (Photo by Tony Hallas):
Galaxy NGC 5195: question mark
The dwarf galaxy NGC 5195 in the constellation Canes Venatici is well known as a small satellite of the spiral galaxy M51, the Whirlpool Galaxy. Together they resemble a cosmic question mark, with NGC 5195 being the point. It is located at a distance of about 30 million light years from Earth. (Photo by Hubble Legacy Archive, NASA, ESA):
Amazing expanding crab
This crab nebula, located 6,500 light-years away in the constellation Taurus, is the remnant of a supernova explosion, an expanding cloud of material left after the explosion of a huge star. The nebula is currently about 10 light-years across and is expanding at a speed of approximately 1000 km/s. (Photo by Adam Block, Mt. Lemmon SkyCenter, U. Arizona):
Variable star RS Stern
This is one of the most important stars in the sky. One of the reasons is that she accidentally found herself surrounded by a dazzling reflection nebula. The brightest star in the center is the pulsating RS Puppis. It is nearly 10 times more massive than the Sun, 200 times larger, and has an average brightness of 15,000 times that of the Sun, with RS Puppis changing brightness nearly five times every 41.4 days. RS Puppis lies about a quarter of the way between the Sun and the center of the Milky Way, at a distance of 6,500 light years. years from Earth. (Photo by Hubble Legacy Archive, NASA, ESA):
Ocean planet Gliese 1214b
Exoplanet (super-Earth) in the constellation Ophiuchus. The first ocean planet discovered, it orbits the dim red dwarf star GJ 1214. The planet is close enough to Earth (13 parsecs, or about 40 light years), and because it transits the disk of its star, its atmosphere can be studied in detail using current technology . One year on the planet lasts 36 hours.
The planet's atmosphere consists of thick water vapor with a small admixture of helium and hydrogen. However, given the high temperature on the planet's surface (about 200 degrees Celsius), scientists believe that the water on the planet is in such exotic states as “hot ice” and “super-liquid water”, which are not found on Earth.
The age of the planetary system is estimated at several billion years. The mass of the planet is approximately 6.55 times the mass of the Earth, while at the same time the diameter of the planet is more than 2.5 times greater than that of the Earth. This picture shows how the artist imagines the passage of the super-Earth Gliese 1214b across the disk of its star. (ESO Photo, L. Calçada):
Stardust in the Southern Corona
Here you can see clouds of cosmic dust that are located in the star field near the border of the constellation Corona Southern. They are less than 500 light-years away and block light from more distant stars in the Milky Way galaxy. In the very center of the image are several reflection nebulae. (Photo by Ignacio Diaz Bobillo):
Galaxy cluster Abell 1689
Abell 1689 is a cluster of galaxies in the constellation Virgo. One of the largest and most massive galaxy clusters known, it acts as a gravitational lens, distorting the light of galaxies behind it. The cluster itself is located at a distance of 2.2 billion light years (670 megaparsecs) from Earth. (Photo by NASA, ESA, Hubble Heritage):
Pleiades
An open cluster in the constellation Taurus, sometimes called the Seven Sisters; one of the closest star clusters to Earth and one of the most visible to the naked eye. This is perhaps the most famous star cluster in the sky. The Pleiades star cluster is about 12 light-years in diameter and contains about 1,000 stars. The total mass of the stars in the cluster is estimated to be about 800 times the mass of our Sun. (Photo by Roberto Colombari):
Shrimp Nebula
Just south of Antares, in the tail of the nebula-rich constellation Scorpio, lies the emission nebula IC 4628. Hot, massive stars, only a few million years old, illuminate the nebula with invisible ultraviolet light. Astronomers call this cosmic cloud the Shrimp Nebula. (ESO Photo):
Despite the difference in size, at the beginning of their development all these stars had a similar composition.
What stars are made of completely determines their character and fate - from color and brightness to lifespan. Moreover, the composition of a star determines the entire process of its formation, as well as the formation of it, including our Solar System.
Any star at the beginning of its life - be it monstrous giants like or yellow dwarfs like ours - consists of approximately equal proportions of the same substances. This is 73% hydrogen, 25% helium and another 2% atoms of additional heavy substances. The composition of the Universe was almost the same after, with the exception of 2% heavy elements. They were formed after the explosions of the first stars in the Universe, whose sizes exceeded the scale of modern galaxies.
However, why then are the stars so different? The secret lies in that “extra” 2 percent of the star cast. This is not the only factor - it is obvious that the mass of the star plays a fairly large role. It determines the fate of the star - it will burn out in a couple of hundred million years, like , or it will shine for billions of years, like the Sun. However, additional substances in the star's composition can overcome all other conditions.
The composition of the star SDSS J102915 +172927 is identical to the composition of the first stars that arose after the Big Bang.
Deep into the stars
But how can such a tiny fraction of a star's composition seriously change its functioning? For a person, on average, consisting of 70% water, a loss of 2% fluid is not terrible - it just feels like intense thirst and does not lead to irreversible changes in the body. But the Universe is very sensitive to even the smallest changes - if the 50th part of the composition of our Sun were even a little different, life might not have formed.
How it works? To begin with, let us remember one of the main consequences of gravitational interactions, mentioned everywhere in astronomy - the heavy tends to the center. Any planet follows this principle: the heaviest elements, such as iron, are located in the core, while the lighter ones are outside.
The same thing happens during the formation of a star from scattered matter. In the conventional standard of star structure, helium forms the core of the star, and the surrounding shell is made up of hydrogen. When the mass of helium exceeds the critical point, gravitational forces compress the core with such force that it begins in the layers between helium and hydrogen in the core.
It is then that the star lights up - still very young, shrouded in hydrogen clouds, which will eventually settle on its surface. Glow plays an important role in the existence of a star - it is those trying to escape from the core after a thermonuclear reaction that keep the star from instantly collapsing into or. Ordinary convection, the movement of matter under the influence of temperature, is also powerful - hydrogen atoms, ionized by heat at the core, rise to the upper layers of the star, thereby mixing the matter in it.
So, what does 2% of heavy substances in the composition of a star have to do with it? The fact is that any element heavier than helium - be it carbon, oxygen or metals - will inevitably end up in the very center of the nucleus. They lower the mass bar, upon reaching which the thermonuclear reaction is ignited - and the heavier the substance in the center, the faster the core ignites. However, at the same time, it will emit less energy - the size of the epicenter of hydrogen combustion will be more modest than if the star’s core consisted of pure helium.
Is the sun lucky?
So, 4 and a half billion years ago, when the Sun had just become a full-fledged star, it consisted of the same material as everything else - three quarters of hydrogen, one quarter of helium, and a fiftieth of metal impurities. Due to the special configuration of these additives, the energy of the Sun became suitable for the presence of life in its system.
Metals don't just mean nickel, iron or gold - astronomers call everything other than hydrogen and helium metals. The nebula from which, according to the theory, it was formed, was heavily metalized - it consisted of the remnants of supernovae, which became the source of heavy elements in the Universe. Stars whose birth conditions were similar to those of the Sun are called population I stars. Such luminaries make up the majority of our planet.
We already know that thanks to the 2% metal content of the Sun, it burns more slowly - this ensures not only a long “life” for the star, but also a uniform supply of energy - important for the origin of life on the criteria. In addition, the early onset of the thermonuclear reaction contributed to the fact that not all heavy substances were absorbed by the baby Sun - as a result, the planets that exist today were able to originate and fully form.
By the way, the Sun could burn a little dimmer - albeit a small, but still significant part of the metals was taken from the Sun by gas giants. First of all, it is worth highlighting, which has changed a lot in the Solar System. The influence of planets on the composition of stars has been proven through observations of a triple star system. There are two stars there that are similar to the Sun, and near one of them they found a gas giant whose mass is at least 1.6 times that of Jupiter. The metallization of this star turned out to be significantly lower than its neighbor.
Star aging and composition changes
However, time does not stand still - and thermonuclear reactions inside stars gradually change their composition. The main and simplest fusion reaction that occurs in most stars in the Universe, including our Sun, is the proton-proton cycle. In it, four hydrogen atoms fuse together, ultimately forming one helium atom and a very large energy output - up to 98% of the total energy of the star. This process is also called the “burning” of hydrogen: up to 4 million tons of hydrogen “burns” in the Sun every second.
How does the star's composition change during the process? This we can understand from what we have already learned about stars in the article. Let's take the example of our Sun: the amount of helium in the core will increase; Accordingly, the volume of the star's core will increase. Because of this, the area of the thermonuclear reaction will increase, and with it the intensity of the glow and the temperature of the Sun. In 1 billion years (at age 5.6 billion), the star's energy will increase by 10%. At the age of 8 billion years (3 billion years from today), solar radiation will be 140% of today's - conditions on Earth by that time will have changed so much that it will exactly resemble.
An increase in the intensity of the proton-proton reaction will greatly affect the composition of the star - hydrogen, little affected from the moment of birth, will begin to burn much faster. The balance between the shell of the Sun and its core will be disrupted - the hydrogen shell will begin to expand, and the helium core, on the contrary, will shrink. At the age of 11 billion years, the force of radiation from the star's core will become weaker than the gravity that compresses it - it is the growing compression that will now heat the core.
Significant changes in the composition of the star will occur in another billion years, when the temperature and compression of the Sun's core will increase so much that the next stage of the thermonuclear reaction will start - the “burning” of helium. As a result of the reaction, helium atomic nuclei first clump together, turning into an unstable form of beryllium, and then into carbon and oxygen. The power of this reaction is incredibly strong - when the untouched islands of helium are ignited, the Sun will flare up to 5200 times brighter than today!
During these processes, the core of the Sun will continue to heat up, and the shell will expand to the boundaries of the Earth's orbit and cool significantly - because the larger the radiation area, the more energy the body loses. The mass of the star will also suffer: streams of stellar wind will carry the remains of helium, hydrogen and newly formed carbon and oxygen into deep space. So our Sun will turn into. The development of the star will be completely completed when the shell of the star is completely depleted, and only the dense, hot and small core remains - . It will slowly cool over billions of years.
Evolution of the composition of stars other than the Sun
At the stage of helium combustion, thermonuclear processes in a star the size of the Sun end. The mass of small stars is not enough to ignite the newly formed carbon and oxygen - the star must be at least 5 times more massive than the Sun for the carbon to begin nuclear transformation.