Welcome everyone to universe evolution.well this a compulsory site one(universe lovers) has to look through.. i'll be posting some thrilling,mysterious facts about our solar system...
STAR'S LIFE & DEATH
Although stars seem constant to us,there is in fact a relentless cycle of life and death going on in a space.Astronomers can identify regions where new stars are being born as well as the remains of stars that have exploded. the stars appear unchanged to us only because they take an almost inconceivably long time - millions & billions of years - to develop. Spectacular and rapid events like a "SUPERNOVA"- a star exploding- are very rare.The course of a star's life and it's eventual death depend on the amount of mass it accrued during it's formation.
how are stars and planets formed?
The life of a star begins with a gigantic cloud of cool hydrogen gas with an initial temperature no more than a few degrees above absolute zero(-273.15^o c). The cloud gradually collapses under it's own gravity and clumps of material begin to form inside it,causing it to collapse at ever increasing speeds,while the temperature of the gas rises steadily.The cloud eventually starts to glow,giving off thermal radiation which can be detected by infrared telescopes.The internal density and temperature ultimately increase to a point where "nuclear fusion" takes place.in which hydrogen is converted into helium,& so a new star is "BORN"
Typically many stars of different sizes emerge from one large gas cloud.Sometimes,stars clusters made up of thousands or even millions of stars are created all at once.A rapidly rotating cloud of gas and dust( the remnants of original cloud) floats around many of the young stars, and inside this cloud there are further clumps of matter which have the potential to develop into planets and other smaller celestial bodies. It is thought that planets may be formed around most stars.
what about age of stars?
The first stars found in the cosmos were formed 400 million years after the big bang.Some stars are very frugal in using their supply of fuel,that even today we are still able to see the stars belonging to the very first generations.This is especially the case with globular clusters,where we find stars that are more than 13 billion years old,although new stars are being formed all the time. One of the best known starbirth regions is the "GREAT ORION NEBULA". which is 1600 light years away and visible with the naked eye as part of the constellation orion. The hubble and spitzer telescopes have revealed that many young stars in the orion region have discs of matter rotating around them in which planets may be forming.
how long does a star live and how do they "die"?
The duration of star's life and the manner of it's death depend on it's "MASS".This is because large,high mass stars use up their energy reserves more rapidly than smaller,low mass stars.This is the reason why large stars shine brightly for no more than a few million years,while smaller stars can live for billions of years.Stars produce their energy as a result of a process known as nuclear fusion- during which hydrogen is converted into helium.However the time inevitably comes when all the hydrogen at the core of a star has been used up.
RED GIANTS & WHITE DWARFS
Once a star's hydrogen reserves are used up, the star enters the final phase of it's life.It swells up to become what is known as "red giant".Our own sun will one day turn into a red giant,and in so doing may even devour the earth,along with several more of inner planets.further fusion processes occur in the core of the enlarged star over millions of years,during which,for example helium is converted in to carbon and oxygen.when all of a star's stock of potential nuclear fuel has benn exhausted,it collapses and turns into a "WHITE DWARF". At this stage the star is only about the same size as "EARTH" and it takes billions more years for it to cool down
When a star has a mass of more than 8 times than that of our sun it's end is considerably more dramatic than that of most regular stars.In it's final stages the dying star hurls it's outer layers into space with a mighty explosion which is called as "SUPERNOVA".
at the same time,the star's interior's collapses to form a small,extremely dense body,which can form either of a "neutron star or a black hole".
The matter in a neutron star is packed as densely as the matter in an atomic nucleus.It is so tightly packed.that a tiny piece of a neutron star the size of a pinhead would weigh more than one million tonnes.The immense pressure in the interior of this kind of object pushes the electrons into the atomic nuclei's protons- leaving nothing but neutrons behind.Neutron stars have a diameter of only about 20 km but contain about the same mass as our sun.
If the mass of a star's collapsing interior is more than about 3 times that of our sun,it's gravity becomes so strong that even the neutrons can't halt the process. Inexorably, the star continues to collapse until it becomes a "BLACK HOLE". the name given to a region where gravity is so powerful that nothing,literally not even light, is able to escape. this is why these gravity holes are "BLACK".