How would the solar system have been different if the disk's center had not been as hot and as dense as it was?
If the temperature and density were less, there would be a possibility that the nuclear reactions of proton-proton chain never would have started the protostar. As a result, it would have remained at the phase of a brown dwarf: a gaseous giant similar to Jupiter, almost not radiating outward. Respectively in the system there was no such phenomena as the Solar wind, the Sun's magnetic field, etc. Because of this effect the Solar system would haven't stayed longer opaque due to the large amount of gas and dust in the form of proto-cloud, Nebula.