AY2
Introduction to Astronomy
Winter quarter, 2013
Instructor: Maria Fernanda (Feña) Duran (mfduran@ucolick.org)
Teaching assistants: Jieun Choi (jchoi37@ucsc.edu)
Katie Hamren (khamren@ucolick.org)
Course web page:
All the information will be there throughout the quarter
www.ucolick.org/~mfduran/AY2
Course Material
Textbook:
The Cosmic perspective 6th edition
Online homework:
www.masteringastronomy.com
Course web page: All the information will be there, updated during the
quarter
www.ucolick.org/~mfduran/AY2
Lectures
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There is a lot to cover
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Combination of slides and some blackboard notes
Read the chapters ahead of time
Lectures will focus on clarifying and demonstrating concepts
We will usually have quizzes/surveys, not graded, just for
feedback.
Grading
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Midterm: 30%
Multiple choice
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Final Exam: 30%
Multiple choice, cumulative.
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Homework: 20%
Discussion Section attendance: 10%
In-class quizzes/surveys: 10%
Homework
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Online at Mastering Astronomy (MA), you need to buy access:
http://www.masteringastronomy.com
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Class code: AY2DURAN2013
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One homework per week, HW0 and HW1 due next week.
Extra time to get MA access.
Posted on Thursday after class.
Due: following Thursday right before class.
Solutions are given as you answer, allowing for instant feedback.
I will post scanned solutions for quantitative problems, a few
days later, so you can compare your answers step by step.
Discussion sections
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Homework related concepts and examples will be discussed
in section.
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Make sure you sign in every time to get credit for
attendance.
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Come prepared! Use your time wisely and have questions
ready.
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Give feedback to your TAs, this will make sections more
useful for both you and your TA.
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If you need more help, come to Office Hours, ask! we can’t
help you unless you say something.
What is this class NOT
about?
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This class is not about “learning the name of the
constellations”
Although we will talk about some history of astronomy,
this is not a history class.
This is a physics class
This is a physics class
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Don’t panic, this is a ‘cool’ physics class
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Only high school level arithmetic and algebra.
No college level math is required to pass this class.
If you feel that math is not your friend, come to office hours
regularly for help.
We will study physical concepts that will allow us to understand the
universe
Math and Units
Metric System
Length: meters
1m = 100cm = 1000 mm
1000m = 1km
Scientific Notation
1000 = 103
0.001=10-3
Distance to the Sun = 150,000,000,000m = 1.5 x 1011m
Wavelength of visible light = 500 nm = 5 x 10-7 m
We (and your calculator) need scientific notation!
Look at appendix C in Cosmic Perspective
Course Outline
Part I: Motion of the Earth, Moon, Sun and Planets
Making sense of what we can see in the night sky.
Gravity: Explaining and predicting motion.
Part II: Light and Energy
Nature of light, light as energy
Interpreting light
Part III: Stars from birth to death
Part IV: Galaxies and the Universe
Our galaxy: the Milky way
Galaxies, Quasars, Black Holes, Relativity
Cosmology, the Big Bang
Take a few moments and fill
out survey #1
Chapter 1: The Big picture
Size and Time Scales of the Universe
Physical scale:
What does the solar system look like?
How far away are the stars?
How big is our Milky Way? How does it compare to other galaxies?
How far away are galaxies?
Time scale:
How much time do we live? how much time do stars live?
how old is the universe?
“When we look at the stars,
we are looking back in time”
Light travels at a finite speed c=299792458 m/s
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It takes 1/7 of a second to go around the Earth
It takes 8 minutes for light to reach us from the Sun
This means we are seeing the Sun as it was 8 minutes ago
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Distance to the nearest star: 3.9x1016m
How long does light take to get to us from that star?
“When we look at the stars,
we are looking back in time”
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Distance to the nearest star: 3.9x1016m
How long does light take to get to us from that star?
Speed of light is c=299792458 m/s or about 3x108m/s
speed = distance/time or time=distance/speed
time= (3.9 x 1016 m) / (3 x 108 m/s) =1.3 x 108 s
turning seconds into years:
time = (1.3x108s)x(1min/60s)x(1hour/60min)x(1day/24hour)x(1year/365days)
time it takes for light to reach us = 4.11 years
When we look at Alpha Centauri we are looking 4 years into
the past!
“When we look at the stars,
we are looking back in time”
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A light year a unit of DISTANCE (not time)
1 light-year is the distance light can travel in one year
How much is it in meters?
“When we look at the stars,
we are looking back in time”
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A light year a unit of DISTANCE (not time)
1 light-year is the distance light can travel in one year
How much is it in meters?
distance = speed x time = 3 x108 m/s x 1 year
1 year (in seconds)=365 days x 24 hours/day x 60 min/1 hour x 60 s/1 min
1 year = 3.1 x 107 s
distance = speed x time = 3 x108 m/s x 3.1 x 107 s = 9.3x1015m
Some definitions
Comet
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Small icy object that orbits a star
Image:
Comet Garradd and M92
Broad dust tail + iron tale
Credit: APOD.
Asteroid
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Small, rocky object that orbits a star
Too small (too little mass) to become spherical under its own gravity
In the picture: asteroid
Vesta as photographed by
the Dawn spacecraft.
Vesta is 500 km across and
is located in the asteroid
belt.
Credit: APOD.
Moon
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Small body object that orbits a planet
Our Moon
Size : 1738 km
Mass: 7.3 x 1022 kg
In the picture: Saturn
and 6 of its moons
Credit: APOD.
Planet
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Moderately massive object that orbits a star
Shines by reflecting light from the star it orbits
May be rocky, icy or gaseous
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Sizes for the solar system : 103 - 7x104 km
Mass range for the solar system : 1022 -1027 kg
Star
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Massive ball of gas, mostly Hydrogen
Generates light and heat via nuclear fusion
Nuclear fusion happens because its own gravity produces extremely high
pressure and temperature in the core.
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Size range : 101 km - 109 km
Mass range : 1028 - 1033 kg
Our Sun: 106 km - 1030 kg
Solar (star) system
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Collection of all the objects listed above: Sun (or a star) , planets, moons,
comets, asteroids.
Open clusters
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Few thousands of stars, few light-years across
In the image: the Pleiades
Credit: APOD.
Globular clusters
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Tens of thousands of stars, all gravitationally bound to each one another
Globular clusters as the
one in the picture, are
about 1017 km across.
They are the oldest
components of our
Galaxy.
Credit: APOD.
Nebulae
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An interstellar cloud of gas
and dust, illuminated by stars
(sometimes dying or forming
stars)
Credit: APOD.
Galaxies
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Many billions of stars all held together by gravity.
Stars live in galaxies, not scattered throughout space.
Credit: APOD.
Clusters of Galaxies
Credit: APOD.
Universe
The sum total of ALL matter
and ENERGY
EVERYTHING in and between
the galaxies
Credit: APOD.
Physical Scales
See interactive animation at http://htwins.net/scale2/
Credit: APOD.