<P> Woolfson recognized 1) monistic, which included Laplace, Descartes, Kant, and Weisacker, and 2) dualistc, which included Leclerc (comte de Buffon), Chamberlin - Moulton, Jeans, Jeffreys, and Schmidt - Lyttleton . </P> <P> In 1978, astronomer A.J.R. Prentice revived the Laplacian nebular model in his Modern Laplacian Theory by suggesting that the angular momentum problem could be resolved by drag created by dust grains in the original disc which slowed down the rotation in the centre . Prentice also suggested that the young Sun transferred some angular momentum to the protoplanetary disc and planetesimals through supersonic ejections understood to occur in T Tauri stars . However, his contention that such formation would occur in toruses or rings has been questioned, as any such rings would disperse before collapsing into planets . </P> <P> The birth of the modern widely accepted theory of planetary formation--the Solar Nebular Disk Model (SNDM)--can be traced to the works of Soviet astronomer Victor Safronov . His book Evolution of the protoplanetary cloud and formation of the Earth and the planets, which was translated to English in 1972, had a long - lasting effect on the way scientists thought about the formation of the planets . In this book almost all major problems of the planetary formation process were formulated and some of them solved . Safronov's ideas were further developed in the works of George Wetherill, who discovered runaway accretion . By the early 1980s, the nebular hypothesis in the form of SNDM had come back into favour, led by two major discoveries in astronomy . First, a number of apparently young stars, such as Beta Pictoris, were found to be surrounded by discs of cool dust, much as was predicted by the nebular hypothesis . Second, the Infrared Astronomical Satellite, launched in 1983, observed that many stars had an excess of infrared radiation that could be explained if they were orbited by discs of cooler material . </P> <P> While the broad picture of the nebular hypothesis is widely accepted, many of the details are not well understood and continue to be refined . </P>

What is the composition of the interstellar cloud that formed our solar system