Is our solar system made up of the debris of old burned-out suns? One popular theory says it is.
Most scientists think that when some ancient stars died, they collapsed, creating many of the elements we have on earth today. Then they exploded as supernovas, blowing matter across space.
In some areas, this debris swirled together with vast amounts of hydrogen and helium.
These turning gas clouds slowly flattened into disks. And as gravity pulled the gases together the pressure became so intense at the center of the cloud that a nuclear fire erupted, which -- in our solar system -- became the sun. Approximately 99% of all matter in our solar system is part of the sun.
Scientists think that some of the heavier atoms remaining in the cloud gradually pulled together to become Earth and the other eight planets of our solar system.
