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Lecture 1

# ASTR 105 Lecture Notes - Lecture 1: List Of Fables Characters, Parsec

Department
Astronomy
Course Code
ASTR 105
Professor
David Bush
Lecture
1

Page:
of 2
ASTR 105 Explorations of the Universe
Unit 1: Our Sky
Chapter 1: Intro to Astronomy
A. Astronomy Definition
A.1. The study of the physical universe
B. Scientific Method
B.1. To figure out how things work, we make an educated guess
(hypothesis)
B.2. Test that guess by experiment/observation
B.3. Revise the guess if needed
B.4. Repeat steps 1-3 to reveal a fundamental rule of nature
C. Scientific Attitude
C.1. When Science tells us that “such & such” is true
C.1.a) Interpret as such and such is true based on our current
understanding
C.2. Revise if contradictory information presents itself
C.2.a) Revise “such & such”
II. Power of Ten Notation
A. The Format:
A.1. Base number x 10Exponent
A.1.a) Base number can be any number
A.1.b) Exponent must be a whole number
B. Examples:
B.1. 482 x 10
B.1.a) = 482 x 10 x 10… (12 factors of 10)
B.1.b) 482 x 10= 482,000,000,000,000
B.2. 57 x 10
B.2.a) = 57 10 10… (9 factors of 10)
B.2.b) 57 x 10 = .000000057
III. Astronomy Distance Units
A. The Astronomical Unit (AU)
A.1. = The average Earth-Sun distance
A.1.a) 1 AU ~ 93,000,000 miles
A.1.b) 1 AU ~ 150,000,000 kilometers
(A.1.b.1) Useful for solar system distances
(A.1.b.1.a) Average Mars-Sun distance ~ 1.52 AU
B. Light Year (ly)
B.1. = The distance light travels in one year
B.1.a) 1 ly ~63,000 AU
(B.1.a.1) Useful for stellar distances
(B.1.a.1.a) Distance to Proxima Centauri (the star
closest to our solar system) ~ 4.2 ly
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C. The Parsec (pc)
D.
D.1. *Ignore above D.*
D.2. 1 pc ~ 3.26 ly
D.2.a) Useful for stellar distances
(D.2.a.1) Distance to Proxima Centauri ~ 1.3 pc
E. The Megaparsec (Mpc)
E.1. 1 Mpc = 1,000,000 pc
E.1.a) Useful for measuring galactic distances
(E.1.a.1) Distance to Andromeda Galaxy (the galaxy closest
to The Milky Way) ~ 213 Mpc
IV. Solar System Distances
Planet Average Planet-Sun Distance (AU)
Mercury .4
Venus .7
Earth 1
Mars 1.5
Jupiter 5
Saturn 10
Uranus 20
Neptune 30
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