Eddington Limit

Definition

The Eddington Limit is the maximum luminosity that a body, such as a star or black hole, can achieve when there is a balance between the outward radiation pressure and the inward gravitational pull. When a massive object exceeds this limit, the radiation force can blow away the surrounding material, affecting how it forms and evolves. Understanding this limit is crucial when looking at the formation of supermassive black holes and the feedback processes in active galactic nuclei (AGN).

5 Must Know Facts For Your Next Test

1. The Eddington Limit is approximately given by the formula $$L_{Edd} = \frac{4\pi G M c}{\kappa}$$, where $$G$$ is the gravitational constant, $$M$$ is the mass of the object, $$c$$ is the speed of light, and $$\kappa$$ is the opacity.
2. Exceeding the Eddington Limit can result in significant mass loss for massive stars and can influence their life cycle by preventing further accretion.
3. In supermassive black holes, the Eddington Limit helps define how much mass can be accreted efficiently without blowing away surrounding gas.
4. During periods of rapid accretion, such as in AGN, exceeding the Eddington Limit may lead to powerful outflows or jets, which can impact galactic evolution.
5. The concept of the Eddington Limit highlights the balance between gravity and radiation pressure, playing a significant role in star formation and feedback processes in galaxies.

Review Questions

• How does exceeding the Eddington Limit influence the formation and evolution of supermassive black holes?
  • Exceeding the Eddington Limit can significantly affect supermassive black holes by limiting their growth through accretion. When a black hole exceeds this luminosity threshold, radiation pressure becomes strong enough to blow away surrounding gas and dust. This reduces the material available for accretion and thus slows down the growth rate of the black hole. Understanding this relationship helps explain why some black holes are observed with high luminosity while others grow more slowly.
• Discuss how AGN feedback mechanisms are related to the Eddington Limit.
  • AGN feedback mechanisms are closely tied to the Eddington Limit because they regulate how energy from an active galactic nucleus influences its host galaxy. When a black hole accretes material at or above the Eddington Limit, it generates intense radiation and winds that can expel gas from the galaxy. This feedback can regulate star formation within the galaxy and contribute to its evolution. By keeping gas from cooling and collapsing into stars, AGN feedback plays a crucial role in balancing galaxy growth with energy output.
• Evaluate the implications of the Eddington Limit on understanding galactic evolution across cosmic time.
  • Evaluating the implications of the Eddington Limit helps us understand how galaxies evolve over cosmic time. The balance it establishes between gravitational attraction and radiation pressure shapes not only individual star formation events but also affects larger-scale structures like galaxies. By limiting mass accretion rates onto supermassive black holes, it influences their growth patterns and overall galactic dynamics. Analyzing these interactions reveals insights into how galaxies regulate their star formation activities and respond to energetic phenomena throughout their lifespans.

Related terms

Luminosity: The total amount of energy emitted by an object per unit time, often used to describe stars and galaxies.

Radiation Pressure: The pressure exerted by electromagnetic radiation on surfaces due to the momentum carried by photons.

Active Galactic Nucleus (AGN): A compact region at the center of a galaxy that is exceptionally bright due to the accretion of material by a supermassive black hole.