Relativistic model for cold spherical interstellar gas clouds

We investigate interstellar gas spheres by determining the metric functions, the material distribution, and the features of particle orbits in terms of stability and geodesics. An exact solution of the Einstein equations for interstellar gas clouds is derived. The solution determines the distribution of pressure and density, and it is suitable to describe the energy, speed, trajectory, and further relevant physical features of the cloud's particles. We describe the space-time inside the nebula and give the density profile and the geodesics of particles. We find that circular orbits are stable and the cloud rotates rigidly at an angular velocity that is inversely proportional to the radius. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)