# ASTR 103 Study Guide - Comprehensive Final Exam Guide - Orbit, Earth, Sun

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20 Nov 2018
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Chapter 1 - Discovering the Night Sky
Scientific Method - a reiterative process based on observations, logic, and skepticism
o Hypothesis - a concept or idea that seems to explain a phenomenon or set of
observations
o Model - a set of hypotheses that have withstood observational or experimental tests
o Theory - a set of related hypotheses can be pieced together into a self-consistent
description of natural observations
o Laws of Physics - theories that accurately describe the workings of physical reality,
and have stood the test of time and been shown to have great and general validity
Order of the Planets
Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Pluto
Star is different than a Quasar - stands for Qazi Stellar
Angle Measurements in Astronomy
The basic unit of angular measure to describe the apparent size of a celestial object - what
fraction of the sky that object seems to cover
The angular diameter (or angular size) of the moon is 1/2 a degree, or the moon
subtends an angle of 1/2 a degree
If you draw lines from you eye to each of two starts, the angle between these lines is the
angular distance between these two stars
The adult human hand provides angle measurements
o The width of the finger (at the tip) - 1 degree
o The width of the hand (at its widest point) - 10 degrees
One degree subdivides into 60 arcminutes
o Minutes of arc
o Abbreviated as 60 arcmin or 60'
Subdivide one arcminute into 60 arcseconds
o Seconds of arc
o Abbreviated as 60 arcsec or 60"
1 degree = 60 arcmin (60')
1 arcmin (1') = 60 arcsec (60")
Prefixes for powers of Ten
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Billion (109)- Giga (G)
Million (106) - Mega (M)
Thousand (103) - kilo (k)
Hundredth (10-2) - centi ( c )
Thousandth (10-3) - milli - (m)
Millionth (10-6) - micro
Billionth (10-9) - nano
Astronomical Distances
Astronomical Unit (AU)
o One AU is the average distance between Earth and the Sun
o 1.496*108 km or 92.96 million miles
Light Year (ly)
o One ly is the distance light can travel in one year at a speed of about 3*105 km/s or
186,000 miles/s
o 9.46*10 km or 63,240 AU
Parsec (pc)
o The distance at which 1 AU subtends an angle or 1 arcsec or the distance from which
Earth would appear to be one arcsecond from the sun
o 1 pc = 3.09*1013 km = 3.26 ly
Naked eye (unaided - eye) astronomy had an important place in ancient civilizations
o Positional astronomy
The study of the positions of objects in the sky and how these positions change
o Naked-eye astronomy
The sort that requires no equipment but human vision
Extends far back in time across all cultures
British Isles Stonehenge
Native American medicine wheel
Aztec, Mayan, and Incan temples
Egyptian pyramids
Eighty-eight constellations in the sky - officially
o Ancient peoples looked at the stars and made groupings
Pictures in the sky
Different cultures different pictures
o We still refer to many of those groupings
o Astronomers call them constellations (From the Latin for "group of stars")
Parts are asterisms
Big dipper is an asterism of the Big Bear
Modern Constellations
o On modern star charts, the entire sky is divided into 88 regions
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