Lect2_1-10_

Lect2_1-10_ - Light Year Speed of light = c = 300,000...

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Light Year Speed of light = c = 300,000 kilometers/second = 186,000 miles per second One light year = distance light travels in a year = 186,000 mi/sec X 3600 sec/hr X 24 hr/day X 365 days = 5.8 X 10 12 miles = 5.8 trillion miles = 3.1 X 10 13 kilometers National debt = $9.2 trillion on Jan 4, 2008 (It increases $1.53 billion per day)
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Some light travel times • Around the Earth 7 times in a second • To the Moon 1.6 sec •T o t h e S u n 8 m i n • To Jupiter about an hour • To Pluto about 5 hours • Nearest star 4 years • Polaris 1000 years • Across galaxy 100,000 years • Nearest large galaxy 2 million years
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Apparent Motions of the Sun, Moon, Planets, and Stars The observer on the curved Earth -- views the sky as a celestial sphere around him. 1. The celestial sphere
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2. Earth’s rotation – the daily motion of the sky The celestial sphere appears to rotate around us
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Earth’s rotation causes -- Stars in the north sky appear to rotate about Polaris. We say they are “circumpolar”. Polaris (North Star) Big Dipper Cassiopeia Looking south, stars rise in the east, reach their highest position due south (“on the meridian”), and set later in the west.
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3. Coordinates in the Sky Like latitude and longitude on Earth: Declination -- same as latitude Right ascension -- same as longitude, but measured in hour, min., and sec.
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coordinates Example: Orion Nebula o 25’ Nowadays a computer controlling the telescope would have the coordinates of thousands of objects in memory There are catalogs of celestial
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Lect2_1-10_ - Light Year Speed of light = c = 300,000...

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