Jeans Mass

Definition

Jeans mass is a critical concept in the study of star formation, representing the minimum mass required for a cloud of gas and dust to gravitationally collapse and form a new star. It is named after the British astrophysicist Sir James Jeans, who first derived the mathematical expression for this mass threshold in the early 20th century.

5 Must Know Facts For Your Next Test

1. The Jeans mass is directly proportional to the square of the sound speed in the cloud and inversely proportional to the square root of the cloud's density.
2. If the mass of a cloud exceeds the Jeans mass, the cloud will undergo gravitational collapse and form one or more new stars.
3. The Jeans mass sets a lower limit on the mass of stars that can form, as clouds below this threshold will not collapse under their own gravity.
4. The Jeans mass is an important concept in understanding the initial mass function, which describes the distribution of stellar masses in a given star-forming region.
5. The value of the Jeans mass can vary significantly depending on the physical conditions within the interstellar medium, such as temperature and density.

Review Questions

• Explain the role of the Jeans mass in the process of star formation.
  • The Jeans mass represents the minimum mass required for a cloud of gas and dust in the interstellar medium to undergo gravitational collapse and form a new star. If the mass of the cloud exceeds the Jeans mass, the cloud will become unstable and begin to collapse under its own gravity, leading to the formation of one or more stars. This mass threshold is a crucial factor in determining the initial mass function, which describes the distribution of stellar masses in a given star-forming region.
• Describe how the physical properties of the interstellar medium influence the Jeans mass.
  • The Jeans mass is directly dependent on the physical conditions within the interstellar medium, such as temperature and density. Specifically, the Jeans mass is proportional to the square of the sound speed in the cloud and inversely proportional to the square root of the cloud's density. This means that clouds with higher temperatures and lower densities will have a larger Jeans mass, while clouds with lower temperatures and higher densities will have a smaller Jeans mass. These variations in the Jeans mass can significantly impact the star formation process and the resulting distribution of stellar masses.
• Analyze the significance of the Jeans mass in the context of the initial mass function and the formation of different types of stars.
  • The Jeans mass is a fundamental concept in understanding the initial mass function, which describes the distribution of stellar masses in a given star-forming region. The Jeans mass sets a lower limit on the mass of stars that can form, as clouds below this threshold will not collapse under their own gravity. This has important implications for the formation of different types of stars, as the initial mass function determines the relative abundance of low-mass, intermediate-mass, and high-mass stars. The Jeans mass, along with other factors such as turbulence and magnetic fields, plays a crucial role in shaping the initial mass function and the resulting stellar population in a star-forming region.

Related terms

Gravitational Collapse:

The process by which a cloud of gas and dust is pulled inward by its own gravity, leading to the formation of a new star or stars.

Virial Theorem:

A fundamental principle in astrophysics that relates the kinetic energy and potential energy of a system in gravitational equilibrium.

Interstellar Medium:

The gas and dust that fill the space between stars, providing the raw materials for star formation.