Eddington Limit

Definition

The Eddington limit, also known as the Eddington luminosity, is the maximum luminosity that a star can reach before the outward radiation pressure overcomes the star's gravitational attraction, leading to the ejection of the star's outer layers. This concept is crucial in understanding the properties and evolution of various astronomical objects, particularly quasars and active galactic nuclei.

5 Must Know Facts For Your Next Test

1. The Eddington limit sets an upper bound on the luminosity of an object, beyond which the outward radiation pressure would overcome the inward gravitational force, leading to the ejection of the object's outer layers.
2. Quasars, which are the extremely luminous active galactic nuclei, can reach luminosities close to or even exceeding the Eddington limit, suggesting the presence of a supermassive black hole at their center.
3. The Eddington limit plays a crucial role in understanding the evolution of quasars and their connection to the growth and development of supermassive black holes in the centers of galaxies.
4. Galaxy mergers can trigger the accretion of material onto the supermassive black hole at the center of the merged galaxy, leading to the formation of an active galactic nucleus (AGN) that may approach or even exceed the Eddington limit.
5. The Eddington limit provides a theoretical upper bound on the accretion rate of material onto a black hole, which is essential for understanding the observed properties and evolution of quasars and other AGNs.

Review Questions

• Explain how the Eddington limit is relevant to the study of quasars.
  • The Eddington limit is crucial in understanding the properties and evolution of quasars, which are the extremely luminous active galactic nuclei. Quasars can reach luminosities close to or even exceeding the Eddington limit, suggesting the presence of a supermassive black hole at their center. The Eddington limit sets an upper bound on the luminosity of an object, beyond which the outward radiation pressure would overcome the inward gravitational force, leading to the ejection of the object's outer layers. This concept helps explain the observed properties of quasars and their connection to the growth and development of supermassive black holes in the centers of galaxies.
• Describe the role of the Eddington limit in the context of galaxy mergers and active galactic nuclei.
  • Galaxy mergers can trigger the accretion of material onto the supermassive black hole at the center of the merged galaxy, leading to the formation of an active galactic nucleus (AGN). The Eddington limit provides a theoretical upper bound on the accretion rate of material onto a black hole, which is essential for understanding the observed properties and evolution of these AGNs. If the accretion rate exceeds the Eddington limit, the outward radiation pressure can overcome the inward gravitational force, potentially leading to the ejection of material from the system. This interplay between the Eddington limit and the accretion process is crucial for understanding the formation and evolution of active galactic nuclei, particularly in the context of galaxy mergers.
• Analyze how the Eddington limit can be used as a probe to study the evolution of the universe.
  • The Eddington limit can be used as a probe to study the evolution of the universe, particularly in the context of quasars and active galactic nuclei. Quasars, which are the most luminous active galactic nuclei, can reach luminosities close to or even exceeding the Eddington limit, suggesting the presence of supermassive black holes at their centers. By studying the properties of quasars, such as their luminosity, redshift, and other observed characteristics, astronomers can gain insights into the growth and evolution of supermassive black holes over cosmic time. This, in turn, can provide valuable information about the formation and evolution of galaxies, as well as the overall structure and evolution of the universe. The Eddington limit, as a fundamental constraint on the accretion and luminosity of these astronomical objects, serves as a crucial tool for probing the dynamic processes that shape the universe on the largest scales.

Related terms

Radiation Pressure: The pressure exerted by the momentum of photons emitted from a luminous object, which can counteract the object's gravitational force.

Accretion Disk:

A rotating disk of dense, accreting material surrounding a central object, such as a black hole or a young star, that is powered by the release of gravitational potential energy.

Supermassive Black Hole:

Extremely massive black holes, typically found at the centers of galaxies, with masses ranging from millions to billions of times the mass of the Sun.