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Ursa Major - Big Dipper

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Ursa Major is one constellation that everyone should learn to recognize. In North America this constellation is commonly called the "Big Dipper." The seven main stars of this constellation are easy to detect even from locations that are not completely dark. A dipper is a long handled spoon or pot. Joining the stars with lines creates a big dipper. As with all constellations, the Big Dipper changes position throughout the night and throughout the year. These changes in position are a result of the earth's motion. Rotating on its axes, and orbiting the sun, our planet is constantly moving. On an evening in Summer the Big Dipper stands over the Northwest horizon. In the Fall of the year, the Dipper sits low over the North horizon. On a Winter evening, the Dipper is standing on end above the Northeast horizon. And in the Spring, the Dipper is high overhead. One of the most important stars in the sky is Polaris. Polaris is commonly called the North Star. Positioned above the Earth's axes of rotation, this star does not move. It is a reliable indicator of true North. Polaris is not a bright star, but if you can locate the Big Dipper, you can locate Polaris. The two stars at the end of the Dipper are the pointer stars. Draw a line through these stars and it will point at Polaris. Through pressing time, we can see that all stars appear to rotate around Polaris. I've shut off daylight in this animation and we can see that over a period of 24 hours that the Big Dipper returns to its starting point. Polaris is a very important navigation star. Measure the angle from the horizon to Polaris and you have determined your latitude. Polaris is also the end star in the constellation Ursa Minor. Commonly called the Little Dipper, this constellation is difficult to see unless you have a dark viewing location. Learn to recognize Ursa Major and it will lead you to Polaris and Ursa Minor, the Little Dipper.

Video Details

Duration: 3 minutes and 18 seconds
Country: United States
Language: English
Views: 308
Posted by: baucis on Jun 15, 2010

Educational video about basic astronomy

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