Eddington Radiation Force Balance

The Eddington limit represents the critical point where the outward radiation pressure from a star's luminosity exactly balances the inward pull of its gravity. When the luminosity exceeds this limit, the outer layers of the star are blown away by the radiation pressure.

Experiment with radiation pressure and gravity

Open Eddington Radiation Force Balance to explore how these parameters affect the star's stability.

1. Set Mass to 1, Opacity to 1, and Scaled luminosity to 1. Notice that the Eddington ratio is 1.0 and the force regime is "Balanced". The inward blue arrows and outward red arrows in the visualization have the same length.
2. Increase the Scaled luminosity to 2. The Eddington ratio becomes 2.0, and the force regime changes to "Radiation dominates". The outward radiation acceleration (2.0) now exceeds the inward gravity (1.0).
3. Reset the Scaled luminosity to 1, and decrease Opacity to 0.5. The Eddington ratio drops to 0.5. With less opacity, the radiation exerts less force on the matter, and the force regime becomes "Gravity dominates".
4. Keep Mass at 1, Opacity at 0.5, and Scaled luminosity at 1. Change the Radius from 1 to 2. Both inward gravity and outward radiation decrease by a factor of 4 (from 1.0 to 0.25, and from 0.5 to 0.125, respectively) due to the inverse-square law. However, the Eddington ratio remains 0.5. The balance between radiation pressure and gravity is independent of the radius.