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16-1 (part 2) | A Solar System is Born. 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.
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The Birth of a Star • As the planets are forming, gas and dustnearthe center of the solar nebula grow dense. • In the center the hydrogen atomsbegin to fuse. • Fusion creates energy that pushes outward. The star begins to shine. • A star is born and a new solar system is formed.
The Structure of the Sun • Corona: Uppermost part of the atmosphere; millions of miles thick • Chromosphere: orange-red layer of atmosphere; thousands of miles thick • Photosphere: the lower atmosphere and what we see • Core: where nuclear fusion occurs
Energy Production in the Sun • The sun has been shining for about 4.6 billion years • Tiny amounts of matter can produce huge amounts 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 the center of the sun, the temperature and pressure are very high • This forces the atoms to collide, causing hydrogen to fuse
Measuring Interplanetary Distances • One way scientists measure distances in space is by using astronomical units (AU) • 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 • Alight-minuteis how far light travels in one minute, which is 18,000,000 km • Distance in the solar system can also be measured in light-hours or light-years