a

. “The process by which an interstellar cloud is concentrated until it is held together gravitationally to become a protostar is not known. In quantitative work, it has simply been assumed that the number of atoms per cm³ has somehow increased about a thousand-fold over that in a dense nebula. The two principal factors inhibiting the formation of a protostar are that the gas has a tendency to disperse before the density becomes high enough for self-gravitation to be effective, and that any initial angular momentum would cause excessively rapid rotation as the material contracts. Some mechanism must therefore be provided for gathering the material into a sufficiently small volume that self-gravitation may become effective, and the angular momentum must in some way be removed.” Eva Novotny, Introduction to Stellar Atmospheres and Interiors (New York: Oxford University Press, 1973), pp. 279–280.

b

. Martin Harwit, Astrophysical Concepts (New York: John Wiley & Sons, 1973), p. 394.

“... there is no reasonable astronomical scenario in which mineral grains can condense.” Fred Hoyle and Chandra Wickramasinghe, “Where Microbes Boldly Went,” New Scientist, Vol. 91, 13 August 1981, p. 413.

c

. “Contemporary opinion on star formation holds that objects called protostars are formed as condensations from the interstellar gas. This condensation process is very difficult theoretically, and no essential theoretical understanding can be claimed; in fact, some theoretical evidence argues strongly against the possibility of star formation. However, we know that the stars exist, and we must do our best to account for them.” John C. Brandt, The Physics and Astronomy of the Sun and Stars (New York: McGraw-Hill, 1966), p. 111.