6.3: The Nebular Theory
So…how did the solar system form and end up with all these different types of objects? Currently the best theory is the Nebular Theory . This states that the solar system developed out of an interstellar cloud of dust and gas, called a nebula . This theory best accounts for the objects we currently find in the Solar System and the distribution of these objects. The Nebular Theory would have started with a cloud of gas and dust, most likely left over from a previous supernova. The nebula started to collapse and condense; this collapsing process continued for some time. The Sun-to-be collected most of the mass in the nebula’s center, forming a Protostar .
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:
- 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.