Astronomy 114
Introduction
Martin D. Weinberg
UMass/Astronomy Department
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Overview (1/4)
What is Astronomy?
Story of our understanding of the Universe
By the end of the course, we will have traveledthrough the solar system, the Galaxy, clusters ofgalaxies to the beginning of the Universe.
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Overview (1/4)
What is Astronomy?
Story of our understanding of the Universe
By the end of the course, we will have traveledthrough the solar system, the Galaxy, clusters ofgalaxies to the beginning of the Universe.
Objectives
Organization of the Universe
Principal components that create this organization
Scientific method: how we try overcome humanperceptual limitations to figure this out
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Overview (2/4)
Scale of the Universe
Sun = basketball
Earth = marble at a few hundred feet
Nearest star = about 10000 miles away (Tokyo)
Center of the Milky Way = 10000 times the neareststar or 100,000,000 miles away
Nearest Galaxy = 1000 times distance to center ofMilky Way 100,000,000,000 miles away
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Overview (3/4)
Human biases
Cosmic length scales—very large compared tohuman size
Cosmic time scales—very long compared to humanlifetime
Cosmic events at many wavelengths—humans havelimited sensitivity to the electromagnetic spectrum
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Overview (4/4)
Three encompassing topics
Motions, Light and Gravity
Stars
Galaxies & Cosmology
A114: Lecture 1—29 Jan 2007 Astronomy 114—5/16
Overview (4/4)
Three encompassing topics
Motions, Light and Gravity
Stars
Galaxies & Cosmology
Text book: Universe by Freedman &Kauffman
A114: Lecture 1—29 Jan 2007 Astronomy 114—5/16
Overview (4/4)
Three encompassing topics
Motions, Light and Gravity
Stars
Galaxies & Cosmology
Text book: Universe by Freedman &Kauffman
My role is to help you understand.Please ask questions!!
A114: Lecture 1—29 Jan 2007 Astronomy 114—5/16
Overview (4/4)
Three encompassing topics
Motions, Light and Gravity
Stars
Galaxies & Cosmology
Text book: Universe by Freedman &Kauffman
My role is to help you understand.Please ask questions!!
Designed for science majors . . .
A114: Lecture 1—29 Jan 2007 Astronomy 114—5/16
Overview (4/4)
Three encompassing topics
Motions, Light and Gravity
Stars
Galaxies & Cosmology
Text book: Universe by Freedman &Kauffman
My role is to help you understand.Please ask questions!!
Designed for science majors . . .
Web site:http://www.astro.umass.edu/˜weinberg/a114
A114: Lecture 1—29 Jan 2007 Astronomy 114—5/16
Requirements (1/3)
Attendance is the single most important way to ensuresuccess in this course.
A114: Lecture 1—29 Jan 2007 Read: Ch. 1-2 Astronomy 114—6/16
Requirements (1/3)
Attendance is the single most important way to ensuresuccess in this course.
Reading: Assignments in the text for each class willbe given at the end of the preceding class and arerequired. The relevant chapters are also listed in theSyllabus by subject.
A114: Lecture 1—29 Jan 2007 Read: Ch. 1-2 Astronomy 114—6/16
Requirements (1/3)
Attendance is the single most important way to ensuresuccess in this course.
Reading: Assignments in the text for each class willbe given at the end of the preceding class and arerequired. The relevant chapters are also listed in theSyllabus by subject.
Exams: Two in-class one-hour exams (each 20% ofthe final grade) and one final exam with two parts:last unit and cumulative. Each part worth 20%.
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Requirements (2/3)
Makeup exam policy: Makeup exams will be given onlyfor documented medical or family emergencies or byprior arrangement.
A114: Lecture 1—29 Jan 2007 Read: Ch. 1-2 Astronomy 114—7/16
Requirements (2/3)
Makeup exam policy: Makeup exams will be given onlyfor documented medical or family emergencies or byprior arrangement.
Homework: There will be (roughly) weekly homeworkassignments worth 20% of the final grade.
A114: Lecture 1—29 Jan 2007 Read: Ch. 1-2 Astronomy 114—7/16
Requirements (2/3)
Makeup exam policy: Makeup exams will be given onlyfor documented medical or family emergencies or byprior arrangement.
Homework: There will be (roughly) weekly homeworkassignments worth 20% of the final grade.
Extra credit: There is none.
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Requirements (3/3)
Grades will be assigned on a modified straight scale.Scores will be adjusted upward if the exam is toohard.
92% A
87% AB
82% B
77% BC
72% C
67% CD
60% D
2 topic exams 40%
1 topic exam at final 20%
1 cumulative exam at final 20%
Homeworks 20%
A114: Lecture 1—29 Jan 2007 Read: Ch. 1-2 Astronomy 114—8/16
Requirements (3/3)
Grades will be assigned on a modified straight scale.Scores will be adjusted upward if the exam is toohard.
92% A
87% AB
82% B
77% BC
72% C
67% CD
60% D
2 topic exams 40%
1 topic exam at final 20%
1 cumulative exam at final 20%
Homeworks 20%
Academic Honesty is expected of all scientists, andalso of all students of science.
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Scientific Notation (1/5)
The numbers encountered in this class are astronomical:
The nearest star is 41,000,000,000,000 kilometersaway
The mass of the sun is2,000,000,000,000,000,000,000,000,000,000,000grams
Scientists have devised a more compact notation fordealing with such numbers called scientific notation.
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Scientific Notation (2/5)
41,000,000,000,000 kilometers
2,000,000,000,000,000,000,000,000,000,000,000grams
There are really only two important parts to each of thenumbers:
1. The leading digits – which establish the precision ofthe number itself
2. The number of digits – which sets the size ormagnitude of the number
In Scientific notation:
4.1×1013 and 2.0×1033
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Scientific Notation (3/5)
The “×" is, as it appears, a multiplication:
102 = 10 × 10 = 100
103 = 10 × 10 × 10 = 1,000
104 = 10 × 10 × 10 × 10 = 10,000
105 = 10 × 10 × 10 × 10 × 10 = 100,000
106 = 10 × 10 × 10 × 10 × 10 × 10 = 1,000,000
so 4.5×104 = 4.5 × 10 × 10 × 10 × 10 = 45,000.
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Scientific Notation (4/5)
Counting zeros and moving the decimal place is aconvenient way of carrying out the multiplication bypowers of tenExample:
Want: 103× 105
103× 10
5= 10 × 10 × 10 × 10 × 10 × 10 × 10 × 10 = 10
8
The result of that long string of multiplication is that weadd the exponents of the 10’s: 3+5=8
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Scientific Notation (5/5)
Addition a bit more tricky:
103+10
5= 10×10×10 + 10×10×10×10×10 = 1.01×10
5
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Scientific Notation (5/5)
Addition a bit more tricky:
103+10
5= 10×10×10 + 10×10×10×10×10 = 1.01×10
5
or
1, 000 + 100, 000 = 101, 000 = 1.01 × 105
A114: Lecture 1—29 Jan 2007 Read: Ch. 1-2 Astronomy 114—13/16
Scientific Notation (5/5)
Addition a bit more tricky:
103+10
5= 10×10×10 + 10×10×10×10×10 = 1.01×10
5
or
1, 000 + 100, 000 = 101, 000 = 1.01 × 105
or
0.01 × 105+ 1.0 × 10
5= 1.01 × 10
5
Rule: add the prefix (mantissa) when power of ten(exponent) for the addends is the same
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Metric Prefixes
10−15 femto-10−12 pico-10−9 nano-10−6 micro-10−3 milli-10−2 centi-10−1 deci-10 deka-102 hecto-103 kilo-106 mega-109 giga-1012 tera-1015 peta-
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Measuring distance
Distance in meters (m)
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Energy Output
Energy Source Total Energy (J)
Big Bang 1068
Radio galaxy 1055
Supernova 1046
Sunlight (1 y) 1034
Volcanic explosion 1019
H-bomb 1017
Thunderstorm 1015
Lightning flash 1010
Baseball pitch 102
Typing (per key) 10−2
Flea hop 10−7
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