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.