Jeans Hypothesis

Jeans’ Hypothesis


in astronomy, a hypothesis of the formation of the planetary system from a filament of material ejected from the sun owing to the attraction of a closely passing star.

The originator of the hypothesis, the British scientist J. Jeans, assumed (works of 1919 and 1920) that the filament, as a result of the gravitational instability arising in it, disintegrates into a number of fragments, which, after cooling, form planets. This hypothesis was part of his more general hypothesis by which he attempted a fourfold application of the principle of gravitational instability to explain the successive formation of galaxies from “primeval chaos,” stars from galactic gas, planets from stars, and satellites from planets. Jeans’ hypothesis was popular in the 1920’s and 1930’s, but its unsoundness was later demonstrated. The American astronomer H. N. Russell (1935) and the Soviet astronomer N. N. Pariiskii (1942) as well as others showed that the material ejected from the sun would have begun to rotate around the sun at a distance of a few solar radii, whereas the radii of the planetary orbits are hundreds and thousands of solar radii. It was also shown that the ejected material with a temperature on the order of millions of degrees would have been dissipated in space.