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Earth and Space Sciences · Glossary

What is Jeans mass, Jeans length?

Also known as: Jeans mass · Jeans length

Definition 1.5 University Earth and Space Sciences — Year 2 · Chapter 1 — The Interstellar Medium and Star Formation

The Jeans mass MJM_J and the Jeans length RJR_J of a gas of given temperature and density are the mass and the radius above which a uniform sphere of that gas collapses under its own gravity (Proposition 1.4).

(a) The Jeans mass against the density of particles for three temperatures (= 2.33). The shaded box marks the masses and densities of observed dense cores: at 10\, K their mass is close to the Jeans mass. (b) The free-fall time of : a third of a million years at 104 particles per cubic centimetre, ten times longer at 102.
(a) The Jeans mass against the density of particles for three temperatures (μ=2.33\mu = 2.33). The shaded box marks the masses and densities of observed dense cores: at 10 K10\,\mathrm{K} their mass is close to the Jeans mass. (b) The free-fall time of Proposition 1.6: a third of a million years at 10410^4 particles per cubic centimetre, ten times longer at 10210^2.
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