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Constellations. What is a constellation?. A group of stars forming a recognizable pattern that is traditionally named after its apparent form or identified with a mythological figure. 88 constellations. History in Constellations. https://www.youtube.com/watch?v=QXeEAQtC75g.
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What is a constellation? • A group of stars forming a recognizable pattern that is traditionally named after its apparent form or identified with a mythological figure. • 88 constellations
History in Constellations • https://www.youtube.com/watch?v=QXeEAQtC75g
Stars were used for Navigation • ancient sailors watched constellations to mark their position.
Importance of the North Star • Polaris, or the North Star, sits almost directly above the North Pole; therefore, it is a reliable gauge of North if you find yourself lost on a clear night without a compass.
Why do stars appear to revolve around polaris? • As the Earth spins on its axis, it also “spins around” the north celestial pole. • Earth's axis points almost directly to Polaris, so this star is observed to show the least movement. • The other stars appear to trace arcs of movement because of Earth's spin on its axis • When looking north, objects in the sky move counter-clockwise.
Will Polaris always be our North Star? • Even though Polaris is the North Star today, this has not always been the case. • The place in the sky that the Earth’s north pole points at changes slowly over time (stellar precession). • In 3000 BC, a faint star called Thuban in the constellation of Draco was the North Star. • The Earth’s axis slowly rotates in a circle every 26000 years .
Polaris, the North Star, lies at the end of the handle of the Little Dipper.
Star Chart • A star chart or star map, is a map of the night sky.
Practice: Make your own Star Map • http://www.cupcakesandthecosmos.com/2016/11/how-to-use-a-star-chart/
https://www.artofmanliness.com/articles/15-constellations-every-man-should-know/https://www.artofmanliness.com/articles/15-constellations-every-man-should-know/
Stars move through space • In addition to their apparent motion, stars are moving through space. • Because the stars are so far away, it is difficult for us to see their motions. • Over thousands of years, however, the movements of the stars can cause the shapes of constellations to change.
Do Stars Move? • Stars move, but because they are so far away and move so slowly, we cannot see their movement easily. • Every night stars seem to rise and set, but it is not the stars that are moving. It is the Earth. • The rotation of Earth causes daytime and nighttime. • Because of Earth’s rotation, the sun moves across the sky during the daytime. For this same reason, the stars seem to move across the sky at night. • All of the stars that you see appear to rotate around Polaris, the North Star. The stars seem to make a full circle around Polaris every 24 hours. • Earth’s tilt and revolution cause the seasons. • During each season, any point on Earth faces a different part of the sky at night. That means that different stars appear in the night sky at different times of the year.
