Formation of Galaxies, Stars, and Planets

Abstract

view Abstract Citations (1) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Formation of Galaxies, Stars, and Planets Strömberg, Gustaf Abstract The galaxy is supposed to have been formed from a primordial gas, extending to dis- tances greater than its present dimensions. The original motions in the gas may be of any kind; in any case, continuous, fluid motion will gradually be established, owing to viscous forces, if the mean free path of the particles of which the gas is composed is smaller than the dimensions of the system. The hydrodynamical laws can then be ap- plied. This implies also that the particles are exceedingly small (atoms or molecules). It is assumed that an approximately steady state of motion is developed, such that the velocities everywherecan be regarded as a finite, continuous, and single-valued function 8-3 1-8-25 Bernhardt 11-22-34 L55-L58-Dec Astro-oo-Stromberg-Wilson-Wilhiams i-~ of position, and that the terms defining the explicit dependence on the time are small in comparison to the inertia terms. It is shown that, if these conditions are satisfied, and if we follow a portion of the gas in its motion, its scalar velocity does not change with time. The motions-at least in the interior of the system-are such that the sys- tem contracts, generally or locally. At the surface there is a loss of matter owing to escape of particles. The contraction proceeds until the gas has developed into one or more bodies. If the system originally had a finite angular momentum, the bodies formed rotate in the same direction as the system. If the system has symmetry about the axis of rotation, the motions in the gas are circular in parallel orbits. If smaller condensations are formed before the larger ones have been developed, the system is very flat. The stars formed after the steady state has been reached also move in circles about the axis and in a common plane. Stars formed before this state was reached may have any rotation and any motion, but the velocity must be less than that of escape. If the relative motion of two massive condensations is circular, then, as long as the gas- eous envelope has sufficient density, the motions in the gas are along "surfaces of zero relative velocity" with constant scalar velocity. Smaller bodies formed from this en- velope move in the same way, but only bodies formed close to a primary can retain this motion after viscous forces and pressure gradients are no longer acting. It is suggested that retrograde sateffites are either captured or formed from the gas when in a locally stable state of retrograde motion corresponding to a near coalescence of the two loops in the known periodic orbits in the problem of three bodies. Application of the theory to the solar system indicates that the planets were not formed in situ but at great distances from the sun. The theory seems to account for the existence of nearly circular orbits for the massive planets and for the general behavior of the motions of the asteroids and the sateffites. If the gas from which the planets were formed was once in the interior of the sun, it may have been expelled either during an encounter with another star or during an explosion like that of a nova. On the first alternative, planetary systems are very rare; on the second, they are a very common phenomenon in the universe Publication: The Astrophysical Journal Pub Date: December 1934 DOI: 10.1086/143608 Bibcode: 1934ApJ....80..327S full text sources ADS |