# Jeans instability

by Cmertin
Tags: instability, jeans
 P: 58 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 $m_{H}[\itex] or I've also seen it as [itex]m_{p}[\itex] in the Jeans length and Jeans mass. The formula is as follows: [itex]M_{J}=(\frac{5×k_{B}×T}{G×μ×m_{H}})^{1.5}×(\frac{3}{4×\Pi×\rho_{0}})^{. 5}[\itex], I know that μ is the average molecular mass. Can someone help me understand this please? I'm a bit confused. I tried looking at the units, though couldn't figure it out. Also, another question about it: Does it work for all masses of ISM? From what I picked up in class, most things don't work for very large objects in astro, and they need more "fudge factors" to work. Is that the same for the Jeans instabilities?  P: 16 Dear Cmertin, H stands for hydrogene, p for proton. The nass measured in that unit is [itex]\mu$! All the best, Yuu