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Inside stars, the process of nuclear fusion takes hydrogen atoms and fuses them together to form helium and heavier elements. Eventually, when the star dies, it will explode and send the material it formed, including carbon, iron, and even heavier elements, outward into space. Watch the video below to see how this happens. That material from the explosion forms a nebula, or cloud of dust and gas in space. When something disturbs the nebula, the matter (all sorts of elements, light and heavy) that it is made of will begin to come together.

Video courtesy of NASA and STScI, copyright permission

 

This is what happened approximately 4.6 billion years ago. A massive star underwent a massive supernova (explosion), sending out a shockwave that disturbed a nearby nebula.

 

Watch the animation below too see how scientists think our solar system formed after our nebula was disturbed by a shockwave from a nearby supernova.

 
The nebula was disturbed enough that it began to spin. As it began to spin, the matter inside started to stick together, stick together, much like the spun sugar does when making cotton candy. The gas and dust inside the nebula began to flatten as its speed increased, forming a disk. Eventually, the matter had formed into larger clumps, with the largest in the center. When the matter in the center was so compressed that there was enough pressure to cause hydrogen atoms to fuse, the beginnings of a new star formed. This was the formation of our sun and its solar system. As the clumps of material that orbited this early sun continued to rotate, all in a counterclockwise direction (if you are looking from the north), they picked up more and more matter and eventually became planets. During the early process of planet formation, while most of the material was still very hot, the heavier elements collected in the middle of the planets (the core of Earth, for example), while the lighter elements stayed closer to the surface.
 

Wondering how the formation of our solar system can be compared to making cotton candy? Watch the explanation below and then click here to watch the demonstration.

 
Eventually, the planets were formed. The inner four planets (Mercury, Venus, Earth, and Mars) were smaller and formed primarily from rocky material. This is because the gaseous material and light elements, such as hydrogen and helium, that the planets started with could not withstand the heat that was put out by the sun. Instead, those materials, including the light gases and ice, collected on the next four planets (Jupiter, Saturn, Uranus, and Neptune) and they came to be known as the gas giants. The heat from the sun is primarily responsible for the four inner “terrestrial” planets and the four outer “gaseous” planets. Pluto was first thought to be a planet, but recent scientific discoveries have determined that it lacks planetary characteristics and therefore is not a planet.
 
Most of the moons formed at the same time as the solar system. However, our moon is believed to have formed afterward when an object larger than Mars struck Earth and caused a large piece of the molten Earth to bounce out into space, cool, and begin orbiting our planet.
 

Analysis:

  1. Why are the inner planets primarily rock?
  2. Draw an illustration showing the sequence described above in the formation of our solar system.
  3. Where did the heavy elements that formed Earth and other planets come from?
  4. Do all the planets orbit the sun in the same direction? Why?
 
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Teachers should view the Teacher Site Map to relate Sci-ber text and the USOE Earth Systems Science core.

 


Updated October 24, 2008 by: Glen Westbroek

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