Understanding Jeans Instability & Masses

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SUMMARY

The discussion focuses on the Jeans instability, specifically the Jeans mass and Jeans length, which are critical in astrophysics for understanding the conditions under which gas clouds collapse to form stars. The formula provided for the Jeans mass is M_{J}=(\frac{5×k_{B}×T}{G×μ×m_{H}})^{1.5}×(\frac{3}{4×\Pi×\rho_{0}})^{.5}, where μ represents the average molecular mass and m_{H} or m_{p} refers to the mass of hydrogen or proton, respectively. The discussion also raises questions about the applicability of the Jeans instability to various masses of interstellar medium (ISM), noting that larger astronomical objects may require additional factors for accurate modeling.

PREREQUISITES
  • Understanding of astrophysical concepts such as Jeans instability
  • Familiarity with thermodynamics, specifically the Boltzmann constant (k_{B}) and temperature (T)
  • Knowledge of gravitational theory, including gravitational constant (G)
  • Basic grasp of molecular mass and its significance in astrophysics
NEXT STEPS
  • Research the implications of Jeans instability on star formation in various environments
  • Study the role of additional factors in modeling large astronomical objects
  • Explore the relationship between temperature and Jeans mass in different astrophysical scenarios
  • Learn about the applications of the Jeans length in cosmology and galaxy formation
USEFUL FOR

Astronomy students, astrophysicists, and researchers interested in stellar formation and the dynamics of interstellar medium will benefit from this discussion.

Cmertin
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I'm trying to understand all the properties of the Jeans instability, the Jeans mass and the Jeans length. I understand the mathematics behind it, though not all the variables. There is a m_{H}[\itex] or I've also seen it as m_{p}[\itex] in the Jeans length and Jeans mass. The formula is as follows:<br /> <br /> M_{J}=(\frac{5×k_{B}×T}{G×μ×m_{H}})^{1.5}×(\frac{3}{4×\Pi×\rho_{0}})^{.5}[\itex], I know that μ is the average molecular mass. <br /> <br /> Can someone help me understand this please? I'm a bit confused. I tried looking at the units, though couldn't figure it out.<br /> <br /> Also, another question about it: Does it work for all masses of ISM? From what I picked up in class, most things don't work for very large objects in astro, and they need more "fudge factors" to work. Is that the same for the Jeans instabilities?
 
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Dear Cmertin,

H stands for hydrogene, p for proton. The nass measured in that unit is \mu!

All the best,
Yuu
 

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