A SOLAR SYSTEM IS BORN Chapter 16 – 1 part 2

The Birth of a Star As the planets are forming, gas and dust near the center of the solar nebula grow dense. In the center the hydrogen atoms begin to fuse. Fusion creates energy that pushes outward. The star begins to shine. A star is born and a new solar system is formed.

Energy Production in the Sun The sun has been shining for about 4.6 billion years. Tiny amounts of matter can produce a huge amount of energy.

Nuclear Fusion Nuclear fusion is the process by which two or more low-mass nuclei fuse to form another nucleus. When hydrogen nuclei fuse they form helium and ignition begins.

Conditions Required for Fusion Under normal conditions, hydrogen atoms never get close enough to join. In center of the sun, the temp. and pressure are very high. This forces the atoms together, so hydrogen can fuse.

Measuring Interplanetary Distances One way scientists measure distances in space is by using the astronomical unit. One AU is the average distance between the Earth and the sun which is 150,000,000 km.

Another Way Another way to measure distances is by using the speed of light. A light-minute is how far light travels in one minute, 18,000,000 km. Distance in the solar system is also measured in light-hours and light-years.

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