What is the biggest sized star that we have identified?

That is not a black hole, neutron star, or white dwarf?



And how did it get so big and stay "stable"?What is the biggest sized star that we have identified?VY Canis Majoris is the biggest star in the universe that is identified



VY Canis Majoris (VY CMa) is a red hypergiant star located in the constellation Canis Major. At between 1800 to 2100 solar radii (approx 2,505,600,000 to 2,923,200,000 km across), it is the largest known star and also one of the most luminous known. It is located about 1.5 kiloparsecs (4.6脳1016 km) or about 4,900 light years away from Earth. Unlike most hypergiant stars, which occur in either binary or multiple star systems, VY CMa is a single star (i.e. does not have any stellar companions). It is categorized as a semiregular variable and has an estimated period of 6,275,081 days, or just under 17,200 years.



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there is a simple principle of how it can stay stable. The galaxy is filled with a very fine substance called the Interstellar Medium (ISM) - dust, gas, molecules and ice particles spread throughout space so thinly that it's sparser than the most perfect vaccuum we can create. Forces in space, like the pressure waves that sweep round spiral galaxies, shockwaves from exploding stars, magnetic fields etc. can correl the ISM together over millions of years into enormous clouds of gas and dust called nebulae, which is where stars form. Nebulae contain huge amounts of gas and dust, and from a distance they may look thick and cloudy, but if you were inside one you probably wouldn't be able to tell - nebular matter is so thinly dispersed. In the night sky you can see many nebulae - they look like little fuzzy patches, but they're actually enormous clouds many light-years across.



Nebulae are usually held up by their own gas pressure or magnetic fields, but a slight disturbance can cause a small, slightly denser region to form within a nebula. This denser region is called a protostar and is the beginning of a star. Protostars will begin to contract under their own gravity, as the gas and dust they're made of pull themselves together. As protostars contract, if they're spinning, the rate at which they spin speeds up, to conserve angular momentum - like an ice skater pulling her arms in while pirouetting on the ice. As the protostar collapses further and further, and spins faster and faster, a swirling disc of dust and gas, called an accretion disc, may form around the protostar, and from this planets may form.



Meanwhile, the protostar heats up as it contracts, and gets hotter and hotter as the gas and dust becomes more and more compressed - and so the protostar begins to glow and shine. The heat and pressure rise inside the shrinking protostar until in its core, at millions of degrees, hydrogen atoms actually fuse together and form helium atoms. This process is called nuclear fusion, and releases huge amounts of energy - but it only happens inside the protostar's core! Hot things expand, and so the incredibly hot core, powered by nuclear fusion, expands and pushes out, trying to make the protostar expands. However, the protostar continues to shrink, its gravity pulling the star inwards, putting the core under even more heat and pressure, so nuclear fusion gets more vigorous, heating the core up... eventually, the core reaches just the right temperature and pressure so that the outwards pressure from nuclear fusion in the core and the inward pull of gravity balance out, allowing the protostar ro reach a stable size. Once this has happened we say the protostar has reached main sequence and is a fully fledged, shining, stable star.What is the biggest sized star that we have identified?VY Canis Majoris is the biggest star identified so far.



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