The Solar System
The Solar System is a collection of nine individual planets revolving around a star called the Sun.
How the Solar System was formed
Scientists hypothesize thaat the solar system formed from part of a nebula of gas, ice, and dust about 4.6 billion years ago. A cloud of material in this nebula was rotating slowly in space. A nearby star might have exploded, and the shock waves from this event could have caused the cloud to start contracting. As it contracted, the matter in the cloud was squeezed into less space. The cloud's density became greater, and the attraction of gravity pulled more gas and dust toward the cloud center. This caused the cloud to rotate faster, which in turn caused it to flatten into a disk with a dense center.
As the cloud contracted, its temperature began to increase. Eventually, the temperature in the core of the cloud reached about 10 million degrees Celsius and nuclear fusion began. A star was born, the beginning of the Dun.
Nuclear fusion occurs when atoms with low mass, such as hydrogen, combine to form heavier elements, such as helium. The new, heavier element contains slighly less mass than the sum of the lighter atoms that formed it. The "lost" mass is converted into energy.
As the cloud contracted, its temperature began to increase. Eventually, the temperature in the core of the cloud reached about 10 million degrees Celsius and nuclear fusion began. A star was born, the beginning of the Dun.
Nuclear fusion occurs when atoms with low mass, such as hydrogen, combine to form heavier elements, such as helium. The new, heavier element contains slighly less mass than the sum of the lighter atoms that formed it. The "lost" mass is converted into energy.