The Eddington limit is the maximum luminosity that can pass through a gas in hydrostatic equilibrium, causing stars or galaxies to blow off outer layers. It is named after Sir Arthur Stanley Eddington and is reached around 120 solar masses. Extremely massive stars could have formed in the earliest years of the universe.
The Eddington limit, also called the Eddington luminosity, is the point at which the luminosity emitted by an active star or galaxy is so extreme that it begins to blow off the object’s outer layers. Physically speaking, it is the maximum luminosity that can pass through a gas in hydrostatic equilibrium, meaning that greater luminosities destroy equilibrium. Hydrostatic equilibrium is the quality that keeps a star round and approximately the same size over time.
The Eddington limit is named after the British astrophysicist Sir Arthur Stanley Eddington, a contemporary of Einstein famous for confirming the theory of general relativity using observations of the eclipse. In a real star, the Eddington Limit is likely reached around 120 solar masses, at which point a star begins to eject its envelope via an intense solar wind. Wolf-Rayet stars are massive stars that exhibit Eddington limit effects, ejecting 001% of their mass via the solar wind per year.
Nuclear reactions in stars are often highly dependent on the temperature and pressure in the core. In more massive stars, the core is hotter and denser, causing the rate of reactions to increase. These reactions produce copious heat, and above the Eddington limit, the outward radiant pressure overcomes the gravitational contraction force. However, there are several models where the Eddington mass limit is precisely, differing by up to a factor of two. We’re not sure if the observed stellar mass limit of ~150 solar masses is a true limit, or we simply haven’t found more massive stars yet.
It is thought that extremely massive stars containing several hundred solar masses could have formed in the earliest years of the universe, about 300 million years after the Big Bang. That’s because these stars had virtually no carbon, nitrogen, or oxygen (only hydrogen and helium), substances that catalyze hydrogen fusion reactions, increasing a star’s brightness. These early stars still fused hydrogen very rapidly and had lifetimes of no more than a million years.
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