"The granddaddy of galactic-formation models was conceived in the early 1960s by three astronomers: Olin Eggen, Donald Lynden-Bell and Allan Sandage. Their 1962 publication played a seminal role in the field and is now simply referred to by the authors’ initials: ELS....According to ELS, the Milky Way began as a spherical cloud of gas—a protogalaxy—that was born collapsing toward its center.The original gas was poor in metals, and so stars formed as the cloud was collapsing would also be metal poor.These newly made stars maintained the kinematic properties of the gas in the collapsing cloud, and so followed eccentric orbits around the center of the Galaxy, forming the population II stars of the halo and the globular clusters. As the cloud contracted, some of its energy would have been lost to heat in a dissipative collapse;"