Away out there in space, there are huge clouds of dust and gas, and if one among those clouds of dust and gas is massive, its own gravity causes it to start to collapse. so it folds in on itself towards the center of that cloud, it gets denser and denser, hotter and hotter and eventually, the particles of that the gas, and therefore the dust are made from are brought so close together, that they start to stick together, they start to fuse; that’s the energy source of a star.
The star switches on and begins to shine Inside every newborn star. hydrogen atoms are fused together to form helium; This process is named fusion, and it creates the energy of each star. What happens to a star during the remainder of its life, depends on how massive it’s at its birth.
A star just like the sun is during a delicate balance between gravity, which wants to form the star collapse in on itself, and the pressure that pushes outward which comes from the energy produced in these fusion reactions at its core. At some point, within the future, the hydrogen runs out. At that time, the core of the star will start to collapse in on itself, under its own weight it gets denser, it gets hotter until the purpose where you’ll actually start to use the helium atoms themselves as the fuel for the fusion pushing helium atoms together, making carbon and oxygen. the next heavier elements on the periodic table. When the star begins to fuse helium, it creates more energy and that causes the outer layers of the star to expand.
One day, our sun will grow so large, it will immerse the inner planets of the system out, as far as the Earth! It will become a red giant. For the sun, this may be the start of the top. What happens is that the outer layers of the star get farther and farther from the center. The force of gravity that they feel, is getting weaker, And the star loses hold of its outer atmosphere. Its outer atmosphere drifts off out into space. It expands to become a planetary nebula. And they’re a number of the foremost beautiful objects within the universe. Once the outer layers have drifted away, all that’s left of the star is its core; A white dwarf star is the dead, remnant core of a star just like the sun at the top of its life, It’s something which may weigh the maximum amount as 1/2 the mass of the sun, but it’s only about the size of the Earth, so it’s an incredibly dense object. It’s dead, there is no fusion happening any longer, it’s incredibly hot, but then over many years, it’ll gradually calm down to become a black dwarf.
Some stars, however, are far more massive than the sun, and they lead very different lives. They are ready to fuse heavier and heavier elements inside their core, the star gets bigger and bigger, some get older to 1000 times the dimensions of our sun until it’s fused elements all the high to iron and once we’ve formed an iron core, there’s no more energy which will be got from fusion that core collapses, the rest of stars starts to collapse in after it, but it bounces off. There’s a huge shock wave and in just a second: BANG! The outer parts of the star are blasted off into space in a huge supernova explosion! These supernova explosions are so powerful, that when one of these stars explodes, it can actually outshine the whole galaxy of which is a component (a galaxy of maybe a 100,000 million stars). For these supergiant stars, all that’s left may be a super-dense core, known as a neutron star, an object which will have a mass greater than our sun, but be less than 20 kilometers across, but for the most massive stars of all, we think that when the core collapses the gravity is so strong, it becomes a region, from which not even light can escape, so stars are literally the places within the universe where the weather are created after the large Bang, our universe contained only hydrogen and helium.
All the other, heavier elements were therefore fused inside stars. The amazing thing is that virtually everything you see around you was made inside a star billions of years ago before the sun and planets were formed, and when that star died and blasted its guts out into space which formed the raw materials from which our sun the planet earth and indeed ourselves were made. And, ultimately, that’s one among the main reasons I feel understanding stars is crucial because it’s actually telling us where we came from.