Lecture 2 - Ch1

# Lecture 2 - Ch1 - Charting the Heavens Ch 1 Physics 1902 We...

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1/6/10 1 Physics 1902 Lecture W.1.b Tools of Astronomy Charting the Heavens – Ch. 1 We are going to try to get some perspective of our place in the solar system, in the universe We need some elements of language to describe our universe This chapter is includes an assortment of observations we can make without instruments and how we interpret them We start with the need for measures for the huge distance scales involved in astronomy 15,000 km 1,500,000 km 150,000,000 km~8 light minutes 3x10 15 km = 3,000,000,000,000,000km = 4 light years Sun α -Cent

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2 1000,000,000,000,000,000 km 10,000,000,000,000,000,000 km Units of Length Clearly the km is not a useful unit We can simply use scientific notation A typical galaxy is 10 18 km across However, it is easier to use units which at some level reflect the scales. For studies of the solar system (or other solar systems) a convenient unit is the Astronomical Unit 1 A.U. is the distance from the Sun to the Earth Units of Length – Cont. Another convenient length scale is the Light year 1 LY is the distance light travels in 1 year 1 LY is 9.46 x 10 15 m or 63,000 AU ‘Nearby’ stars are about 4 LY from us 1 AU is about 8 light minutes We will introduce another scale (parsec) when we discuss how distances to stars are measured 1 pc ~ 3 LY Constellations What is the physical relationship among these stars? The stars project a pattern but may be
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Lecture 2 - Ch1 - Charting the Heavens Ch 1 Physics 1902 We...

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