Spherical Jeans equation and anisotropy
Research context
research method · conditional · As of 2026-10-10
The stationary spherical nonrotating Jeans moment equation connects tracer density and radial velocity dispersion to enclosed mass through velocity anisotropy.
Key knowledge
The stationary spherical nonrotating Jeans moment equation connects tracer density and radial velocity dispersion to enclosed mass through velocity anisotropy. Its outer-pressure boundary enters the solution. Different mass and anisotropy profiles can reproduce the same projected dispersion.
Values and equations
d(ν σr^2)/dr + 2βνσr^2/r = -ν G M(<r)/r^2; β=1-(σθ^2+σφ^2)/(2σr^2)
- ν
- Tracer number density m^-3
- σr,σθ,σφ
- Velocity dispersions m s^-1
- β
- Velocity anisotropy 1
- M(<r)
- Total gravitating mass inside r kg
- r
- Spherical radius m
- G
- Gravitational constant m^3 kg^-1 s^-2
Conditions and scope
- Require collisionless approximate equilibrium, spherical symmetry and a known tracer profile.
- Streaming, tides, binaries and interlopers need additional terms or observation models.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
The Jeans equations: Spherical nonrotating moment equation, anisotropy and boundary integral (selected source body inspected).
2026-10-10 · Bounded source check of the recorded statement and conditions. This does not certify a unique physical model, reproduce the cited study or replace independent branch review.
Entry details
Permanent link to this entry ↗- Record identity
- research-earth-spherical-jeans
- Revision
- research.1
- Structured reference record
- Postgraduate & research reference