Why Do Solar Systems Need a Star?
For the Milky Way, that gravitational pull is the sun. And other than sustaining life on this planet, it also helps to keep other planets from flying out of orbit.
How Did our Solar System Come to Be?
About 4.6 billion years ago, there was nothing in our solar system, but clouds of dust called the Nebula. A Supernova explosion took place near our solar system, disrupting the Nebula.
Are There Other Solar Systems?
NASA has discovered nearly 500 other solar systems. For something to be called a solar system, it has to have a system of 2 or more planets orbiting a star.