The life span of a star is very long. If we observe the different states of the stars of our native galaxy ‘Mandakini’. So the life cycle of a star can be understood. The life cycle of a star is generally kept in the following stages. example Gas Cloud
The life of a star begins with the formation of clouds of hydrogen and helium in the third arm of the Milky Way. These clouds are called Stellar Nebula.
Protostar
When the cloud of hydrogen in the galaxy is very large, then the gaseous body starts shrinking due to the effect of gravity, then it is called a protostar. Its center is dense, that is why it is also called Embryo Star.
Star Formation UPSC
The number of collisions between atoms in the clouds of gas increases as the primordial star shrinks. The process of contraction continues for one billion years and the internal temperature increases infinitely. As a result, nuclei of helium start forming from hydrogen. This releases an unlimited amount of radiation energy. This increases the pressure and temperature inside. This state is known by the name of ‘Tara’. A star is small, medium or heavy according to its mass. After coming in this condition, the star starts its life.
Due to the increase of pressure inside the star itself, further centralization of gaseous substances is stopped. Gravitational force in stars produces compression and the other force is due to the internal pressure generated due to the energy released by the fusion reaction. There can be a balance between these two forces for thousands and billions of years. If there was no internal pressure generated due to the free energy in the fusion, then due to the effect of huge gravitational force, the star or the Sun would have shrunk within half an hour of its origin. The Sun is in the said balanced phase of its evolution, the most important thing about stars is that its life cycle is determined by the amount of matter (their mass) present in them.
Blood-Giant
As nuclear fusion reactions take place in the center of the star, its hydrogen gets converted into helium. Therefore, after some time helium becomes dominant in its core and nuclear fusion reactions stop. Due to this the pressure in the core decreases and the star starts shrinking. But the hydrogen in the outer shell of the star starts fusing into helium and the intensity of energy radiation decreases. A star in this stage is called a red-giant star because its color changes to red.
The fate of a star once it reaches the ‘red giant’ stage depends on its initial mass. Nobel Prize-winning Indian-American astrophysicist S. According to Chandrasekhar, 1.44 solar mass is the upper limit of the mass of a white dwarf. It is also called Chandrashekhar limit. That is, if the mass of a star is less than or equal to the mass of the Sun (Chandrasekhar limit), then it changes from a ‘red giant’ to a white dwarf and finally to a black dwarf and if the mass of the star is greater than or equal to that of the Sun. If it is many times more, then after the supernova explosion corresponding to the mass, it gets converted into a neutron star or a black hole.
Red Giant
When the mass of a red giant is equal to or less than the mass of our Sun, its outer shell expands and eventually disappears. The remaining core is gradually compressed and remains as a ball of matter of high density. As a result, the temperature of the core increases to a great extent, due to which the nuclei of helium begin to fuse into elements such as carbon. Due to the low energy released as a result of the fusion of helium, this code becomes bright like a white dwarf. It will remain bright until all its helium is converted into nuclei of high mass. It is noteworthy that the diameter of a white dwarf with a mass equal to that of the Sun will be one percent of the diameter of the Sun, that is, approximately that of the Earth.
Will be equal in size. It is known that the structure of white dwarf was first known by R. Planted by H. Fauber.
Black Dwarf
A white dwarf star is a fossil star. When the helium in the core of a white dwarf is gradually exhausted, it does not emit energy and light and cools down to become a dense black dwarf star. That is, the white dwarf gradually disappears by becoming a black dwarf. It is known that black dwarf is different from black hole or black hole.
Those stars whose mass is many times more than the mass of the Sun (Chandrasekhar limit 1.4), their end is more cataclysmic. Such stars pass through the states of supernova or neutron star or black hole according to the excess of mass. In a massive star, the above states can also be found in sequential form.
Supernova
Such stars which are several times heavier than the Sun and attain the red-giant stage, their core shrinks due to extreme gravity and the helium of the core is converted into carbon due to extreme increase in temperature. This carbon is gradually converted into heavy substances like iron. * In the end, the center of the star becomes filled with iron, as a result of which the process of nuclear fusion in the center stops. As a result, the middle layer of the star collapses at the center of the star due to gravity. The energy released from this blows away the upper layer of the star. This is considered the terrible explosion of the universe. This is called a supernova explosion. For a short time, a supernova star becomes as bright as the entire Milky Way. After the supernova explosion, shock waves and clouds of gases emerge from the supernova. A new generation of stars is created from this gaseous cloud.
Neutron Star
When a massive star reaches its final stage, it undergoes a supernova explosion. Neutron stars are formed from the remaining central part of this explosion, which is of high density and a few miles in diameter. Everything in a neutron star is organized in the form of neutrons. It rotates on its axis 30 times in a second and emits intense radio waves. * The concentration of radio waves is highest at the magnetic poles. This star was first detected by Miss Jocelyn Bell in 1967. Some astrophysicists named neutron stars as pulsars because of the emission of pulsating radio waves by neutrons.
Black hole
The infinite mass of a neutron star eventually gets concentrated at a single point. A body containing matter of such infinite density is called a black hole. In other words, large compressed stars which become invisible are called ‘Black hole’. * Its gravitational power is so high that even light cannot escape from it.
The formation of a black hole depends on the mass contained in the core of the collapsed star. Stars whose mass is less than three times the mass of the Sun disintegrate into neutron stars. * But who-
The mass of stars is more than three times the mass of the Sun, they disintegrate and eventually result in black holes.
Black Hole: Hawking’s Thoughts
Based on the equations of Einstein’s theory of relativity, it is concluded that the origin of the universe is due to a great explosion in a Point of Singularity with infinite density. Scientists believe that all the laws of physics break down at this point because no law or theory is capable of understanding the state of infinite density of this point. However, Stephen William Hawking, known as ‘modern Einstein’, shook the old rules by giving a new idea about this point of singularity. According to the laws of physics, black holes or black holes can only consume matter and energy, not emissions, while Hawking says that black holes also emit radiation. Hawking made this conclusion by applying the laws of quantum mechanics to black holes.
According to the principles of quantum mechanics, the universe is nowhere completely empty, even the vacuum is not an exception. According to this, even in vacuum, the formation or destruction of virtual pair particles goes on continuously. This process of formation and destruction of particles is so fast that it is neither possible to see nor measure it. Yes, the effects of these particles can be measured. In vacuum, when such virtual pairs of particles are formed near the event horizon of the black hole (where the boundary of the black hole ends), then the particle with negative energy is attracted by the black hole while the particle with positive energy is thrown out. goes into space. Actually, in these pairs of particles, one is a particle and the other is its antiparticle. All these events happen very fast. A particle traveling into outer space appears to emit radiation from a black hole. This radiation is called ‘Hawking Radiation’.
This particle dropped in the outer space also takes energy with it and thus there is a decrease in the energy of the black hole, which is known as the ‘evaporation’ of the black hole. Also, according to Einstein’s equation, the mass of the black hole also decreases. As a result, the area of the event horizon of the black hole goes on decreasing. According to Hawking, while evaporating, the black hole changes into the shape of a small sphere whose diameter is equal to the Planck length (10-35 meters). If a black hole radiates more energy, it ceases to exist, so in principle a distance less than the Planck-length has no significance. In this way, bypassing the point of singularity, equations related to the origin of the universe can be formed.
Hawking has considered time as imaginary in his theory because no singularity exists in imaginary time itself. Accordingly, Hawking has imagined such a universe which has no edge, no boundary and which has no beginning and no end. Hawking believes that this expanding universe will reach its maximum size after expanding to a limit and then shrinking down to its original size.
Stella Stars
Due to being covered by dense clouds of astronomical dust particles in distant deep space, it is not possible to see countless celestial objects from terrestrial optical telescopes. But the infrared telescope installed in the Spitzer Space Telescope can easily see even among these dense clouds. This powerful telescope has detected millions of stars in their infancy, 5400 light-years away from Earth, in dense dark clouds of celestial dust particles in space. These stars are called ‘Stella Stars’.
The Spitzer Space Telescope, engaged in discovering the secrets of infinite space, has detected millions of Stella stars among dense bright clouds in a nebula called ‘Triffid Nebula’. The process of origin and evolution of these stellar stars is very rapid. Their distance from the earth is about 6 trillion km.
Blood Giant Star Swallowing Planets
In November 2003, the Hubble telescope was able to capture the scenes of a giant star swallowing up three planets one after the other. In fact, till now it was believed that big stars swallow planets, but scientists probably got the opportunity for the first time to take pictures of such an event. Alan Ritter from the University of Sydney, Australia, said, “Until now it has been heard or read that giant stars swallow planets, but we hope that we have the privilege of seeing and photographing such scenes, perhaps for the first time.” This star named ‘B 825’, which swallows three planets, is located at a distance of 20 thousand light years from the Earth. of scientists
In January 2000, it temporarily became the brightest star in the Milky Way. At that time its brightness was estimated to be six lakh times more than that of the Sun. It was a red giant star that expanded and successfully swallowed three planets one after the other. There was a gap of only two months between the first and the third event of planetary swallowing by ‘B825’. After strong evidence of the event of a star swallowing planets, the question has arisen that a billion years from now, what will happen when the Sun becomes a red giant? Scientists estimate that then it may make both Venus and Mercury its prey.
What will be the future of the earth? Nothing can be said about this now. Rader says that our discovery shows that after swallowing a planet, the star explodes again and this process continues. In such a situation, the earth may also be swallowed by the sun. But now it is a subject of research.
