51 The Nebular Theory
A protostar is an object in which no nuclear fusion has occurred, unlike a star that is undergoing nuclear fusion. A protostar becomes a star when nuclear fusion begins. Most likely the next step was that the nebula flattened into a disk called the Protoplanetary Disk ; planets eventually formed from and in this disk.
Three processes occurred with the nebular collapse:
- Temperatures continued to increase
- The solar nebula spun faster and faster
- The solar nebula disk flattened
The orderly motions of the solar system today are a direct result of the solar system’s beginnings in a spinning, flattened cloud of gas and dust.