Gravity Darkening

Gravitational darkening is an astronomical phenomenon when a star rotates so fast that it has a flattened shape, such as, for example, in Regulus . When a star is flattened, its radius at the equator is greater than at the poles. As a result, at the poles, the acceleration of gravity is greater, and, consequently, more temperature and brightness ^{[ why?} ^] . Thus, the poles experience gravitational lightening , and the equator is gravitational darkening ^[1] .

The star becomes flattened, since the centrifugal force as a result of rotation creates additional external pressure at the equator of the star. Centrifugal force is expressed by a mathematical expression:

F_{\text{центробежная}}=m\Omega ^{2}\rho ,

{\ displaystyle F _ {\ text {centrifugal}} = m \ Omega ^ {2} \ rho,}

{\ displaystyle F _ {\ text {centrifugal}} = m \ Omega ^ {2} \ rho,}

Where $m$ ${\ displaystyle m}$ $m$ - mass (in this case, a small element of the volume of the star), $\Omega$ ${\ displaystyle \ Omega}$ $\ Omega$ - angular velocity $\rho$ ${\ displaystyle \ rho}$ $\ rho$ - radial distance from the axis of rotation. In the case of a star, $\rho$ ${\ displaystyle \ rho}$ $\ rho$ becomes larger as you move along the meridian from the pole to the equator. This means that the equatorial regions of the star will have a greater centrifugal force, compared with the poles. The centrifugal force repels the mass from the axis of rotation, and leads to a decrease in the total pressure on the gas in the equatorial regions of the star. This will lead to the fact that the gas in this region will become less dense and colder.

Notes

↑ The Mysterious Phenomenon of "Gravity Darkening" (neopr.) . io9 .

[io9-1] The Mysterious Phenomenon of "Gravity Darkening" (neopr.) . io9 .

Gravity Darkening

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Notes

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