Interstellar Solid Hydrogen: How Much and Where?

Abstract

FOLLOWING the suggestion that hydrogen may freeze onto grains in some interstellar clouds^1,2, recent calculations have indicated that the grain temperatures will not become low enough^3–5. The calculations are uncertain, however, because the grain models are in doubt⁶ and because little is known about the physical and chemical properties of solid particles and their surfaces in interstellar conditions of temperature, pressure and radiation loading. On the other hand, it has been shown that the properties of galaxies of stars formed from clouds of solid hydrogen grains would possess several features which accord with observation^7–9.