![]() ![]() Most of the stars in the universe, about 90 per cent of them including the sun, are main sequence stars. Main sequence stars fuse hydrogen atoms to form heliumin their cores.That is why nuclear fusion is hard to achieve and control ). It occurs only when the initial temperatures are very high- a few million degrees Celsius. Nuclear fusion : the fusion of 2 hydrogen atoms into a helium atom with the liberation of a huge amount of energy.Protostars are usually surrounded by dust, which blocks the light that they emit, so they are difficult to observe in the visible spectrum. The luminosity comes exclusively from the heating of the Protostar as it contracts (because of gravity). A Protostar looks like a star, but its core is not yet hot enough for nuclear fusion. ![]() White dwarf (in case of a small star)and Neutron Staror Black Hole (in case of a large star).Planetary Nebula (in case of a small star) and Supernova (in case of a large star).Red Giant (in case of a small star) and Red Supergiant (in case of a large star)., Sun – full of life ( nuclear fusion at the core is in full swing). T Tauri Star : a young star still undergoing gravitational contraction it represents an intermediate stage between a Protostar & a low-mass main sequence star.Protostar : an early stage of a star formation where nuclear fusion is yet to begin.Nebula : a cloud of gas (mostly hydrogen and helium) and dust in space.Outlined below are the steps involved in a star’s evolution, from its formation in a nebula, to its death as a white dwarf or a neutron star. ![]()
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