ASTRONOMY 1020: ASTRONOMY OF THE UNIVERSE

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ASTRONOMY 1020 ASTRONOMY OF THE UNIVERSE
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PROFESSOR Dr. Kae P. Gershon

• A.A. (DeKalb Community College now GA Perimeter 
  College),
• B.S. (GSU), 
• M.S. (GSU),
• PhD. (Emory University) 
• Assistant Professor   of Astronomy.

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SOME USEFUL LINKS

• Fernbank science center homepage
  http//fsc.fernbank.edu/Universe Website
  http//bcs.whfreeman.com/universe6e/pages/bcs-main
  .asp?vs01000n00010i01010.01o
• Hyperphysics Concepts GSU http//hyperphysics.
  phy-astr.gsu.edu/hbase/astro/astcon.html -
  astcon
• Phases of the Moon http//www.go.ednet.ns.ca/la
  rry/orbits/lunrphas.htmlAstronomy Picture of the
  Day http//antwrp.gsfc.nasa.gov/apod/astropix.htm
  l
• Powers of Ten Demo http//micro.magnet.fsu.edu/p
  rimer/java/scienceopticsu/powersof10/ 

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PHASES OF THE MOON

• We will study this in much more detail later, but
  these are the 8 phases of the moon you will need
  if you work on an observational logbook (see
  course contents).
• A test question that could be on any quiz or exam
  is What is the phase of the Moon TONIGHT?

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INTRODUCTION

• Astronomy is the study of - basically -
  EVERYTHING in the Universe.
• Astronomy has many sub-branches including
  galactic, planetary, biology, physics, geology,
  life, etc.

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• Astronomy and the
  Universe
• An eclipse over
  Africa
  
• 
  (APOD)

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Guiding Questions

• What methods do scientists use to expand our
  understanding of the universe?
• What makes up our solar system?
• What are stars? Do they last forever?
• What are galaxies? What do astronomers learn by
  studying them?
• How does measuring angles help astronomers learn
  about objects in the sky?
• What is the powers-of-ten notation, and why is it
  useful in astronomy?
• 7. What math concepts are necessary?
• 8. Why do astronomers measure distances in
  astronomical units, light-years, and parsecs?
• 9. How does studying the cosmos help us on Earth?

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THE ORIGIN OF THE UNIVERSE

• The Universe began from "NOTHING" in an event
  called the BIG BANG.
• The original temperature was nearly infinite (?).
  When the early universe cooled enough to form
  atoms, aggregations of matter began to form.
• These eventually became stars and galaxies, our
  own galaxy, the Milky Way Galaxy, also formed.

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Quasar about 10 million years after The Big Bang
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Our Solar System

• was formed from a cloud of gas and dust.
• It is thought that the cloud was started on its
  collapse to the Sun and planets by the gigantic
  explosion of a HUGE star in a supernova explosion
  near our cloud.

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Eta Carina Nebula a pre-solar system nebula
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The pressure on the cloud

• made it spin faster and faster while gravity
  pulled the matter into clumps.
• The cloud flattened as it spun faster until it
  became almost totally planar.
• The clumps became planets and moons. The biggest
  clump (by a factor of 1,000,000 times the volume
  of Earth) became the Sun.

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This happened about

• 4.6 BILLION years ago.
• The Earth formed a twin-planet system of the
  Earth and the Moon.
• Originally all the planets and larger moons were
  molten.
• As the Earth cooled seas formed and life was
  created within these seas at least 3.5 billion
  years ago.
• Life evolved and we are here, now. 

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WHAT WE SEE FROM ATLANTA

• From Atlanta and the Earth we see many
  remarkable things, although not as much in cities
  like Atlanta as in the countryside.
• We can see the Sun
• http//sohowww.nascom.nasa.gov/,
• over 2000 individual stars
• http//hubble.stsci.edu/gallery/showcase/index.sht
  ml ,

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WHAT WE SEE FROM ATLANTA

• the Milky Way Galaxy containing billions of stars
  
• http//antwrp.gsfc.nasa.gov/apod/ap990224.html ,
• http//antwrp.gsfc.nasa.gov/apod/astropix.html ,
• some of our companion galaxies in the Local Group
  of galaxies
• http//hubble.stsci.edu/gallery/showcase/index.sht
  ml ,
• glowing clouds called nebulae,
• http//hubble.stsci.edu/gallery/showcase/nebulae/n
  5.shtml ,

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WHAT WE SEE FROM ATLANTA

• five planets
• http//hubble.stsci.edu/gallery/showcase/index.sht
  ml ,
• and, last but NOT least, the Moon.
• http//nssdc.gsfc.nasa.gov/imgcat/html/ency_captio
  ns/moon.html
• http//tycho.usno.navy.mil/vphase.html
•  

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DISTANCES

• The distances to all these objects are enormous,
  from about
• 400,000 km to the Moon to
• 2 million light years 1.9 1012 km to the
  Andromeda Galaxy, the farthest naked-eye object.

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To understand the universe, astronomers use the
laws of physics and construct testable theories
and models.

• Scientific method
• Based on observation, logic, and skepticism.
• Hypothesis
• A collection of well thought-out ideas to explain
  a phenomena
• Model.

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• Model.
• Hypotheses that have withstood observational and
  experimental tests.
• TheoryA well-founded body of related hypotheses
  and models that form a self-consistent
  description of nature.

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By exploring the planets, astronomers uncover
clues about the formation of the solar system.
Solar system one star (the Sun), at least eight
planets, nearly 100 moons, countless asteroids
and comets.
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By studying stars and nebulae, astronomers
discover how stars are born, grow old, and die.
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By observing galaxies, astronomers learn about
the origin and fate of the universe.
Galaxy an isolated collection of stars
numbering in the hundreds of thousands up to
hundreds of billions of stars.
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Astronomers use angles to denote the positions
and apparent sizes of objects in the sky.
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Angular Measure

• Basic unit of angular measure is the degree º
• Full circle measures 360º
• Right angle measures 90º
• Angular distance is the number of degrees across
  the sky between two points.
• Angular diameter or angular size is the number of
  degrees from one side of an object to the other
  side.
• FORMAL The angular size of the Moon is 0.5º
• INFORMAL The Moon subtends an angle of ½º

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Angular Measure for Small Angles

• 1º 60 arcminutes 60
• 1 60 arcseconds 60
• e.g., On January 1, 2001, the planet Saturn had
  an angular diameter of 19.7 as viewed from Earth

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The Small-Angle Formula D a x d 206,265
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Example On November 28, 2000, the planet Jupiter
was 609 million kilometers from Earth and had an
angular diameter of 48.6. Using the small-angle
formula, determine Jupiters actual diameter.

• D 48.6 x 609,000,000 km 206206 143,000 km

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Powers-of-ten notation is a useful shorthand
system of writing really large numbers.
100 1 101 10 102 100 103 1,000 104
10,000 106 1,000,000 109 1,000,000,000
One Ten (deca-) Hundred (centa-) Thousand
(kilo-) Ten thousand Million (mega-) Billion
(giga-)
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Powers-of-ten notation is a useful shorthand
system of writing really small numbers.
100 1 10-1 0.10 10-2 0.01 10-3 0.001 10-4
0.0001 10-6 0.000001 10-9 0.000000001
One One-tenth (deci-) One-hundredth
(centi-) One-thousandth (milli-) One-ten-thousandt
h One-millionth (micro-) One-billionth (nano-)
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THE SCALE OF THINGS EXAMPLE

• 1,230,000,000 1.23 109.
• 0.00000000258 2.58 10-9.
• http//micro.magnet.fsu.edu/primer/java/scienceopt
  icsu/powersof10/ .
• Powers-of-ten are usually written in scientific
  notation.
• The format is X.xx 10n for 3 significant
  figures, which is common in astronomy.

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Numbers that are of normal size may or may not be
written in scientific notation.

• The integer 1 may be written as
• 1 1.00. 1.00 100 100. 

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SIGNIFICANT FIGURES

• The significant figure of the result of
  multiplication or division is the least number of
  digits of any of the factors.
• For addition and subtraction the significant
  figure is the least number of decimal places of
  any of the numbers.

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In practice we just put

• all the numbers with all their digits into the
  calculator and then reduce the answer to the
  correct number of significant figures in
  scientific notation. 

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EXAMPLE

• 356,875,355.2 22 7,851,257,814.4
• 7.8 109
• with 2 significant figures in scientific
  notation.
• Using a calculator
• 356,875,355.2 22 7,851,257,814.4,
• would be entered as written.

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Your calculator may or

• may not
• give it to you in the form of
• 7.85 109,
• but you would need to know to put this and the
  previous answer in the correct number of
  significant figures
• 7.8 109.  

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EXAMPLE

• 356.354 22.2 1.58 3.2
• 376.934
• 376.9
• with 4 significant figures. 

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METRIC UNITS

• The Systeme International (S.I.) set of metric
  units has 7 standard, fundamental units
• the meter (m),
• second (s),
• kilogram (kg),
• ampere (A),
• candela (cd),
• mole (mol), and
• Kelvin (K).

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All other units

• can be expressed as combinations of these.
• In science English units are never acceptable.
• A couple of useful conversions to keep in mind to
  help appreciate the sizes of metric units are
• 2.540centimeters 1.0. inches and
• 2.2 kilograms ? 1 lb. 

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Astronomical distances are often measured in
astronomical units, parsecs, or light years.
Astronomical Unit (AU) One AU is the average
distance between Earth and the Sun (1.496 X 108
km or 92.96 million miles). Light Year (ly) One
ly is the distance light can travel in one year
at a speed of about 3 x 105 km/s or 186,000
miles/s (9.46 X 1012 km or 63,240 AU). One Parsec
(pc) One pc is the distance from which Earth
would appear to be one arcsecond from the Sun.
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One Parsec (pc)One pc is the distance from
which Earth would appear to be one arcsecond from
the Sun.
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ASTRONOMICAL DISTANCES

• And units
• These are usually measured in
• astronomical units (AU),
• parsecs (pc), or
• light years (LY).

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An AU 1.5 108 km is the

• distance from the Earth to the Sun.
• A LY is the distance light travels in a vacuum in
  one year.
• Light travels at
• c 2.9979 108 m/s
• 3.00 108 m/s 3.00 105 km/s.
• (Know the speed of light for tests!)
• A LY 63,200 AU. 1 pc 3.26 LY.

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Solar Units involve writing the

• HUGE units that describe the Sun as units of the
  Sun.
• The mass of the Sun is
• 1 M0 1.989 1030 kg and the
• solar radius 1 R0 6.9599 108 m.
• Light is measured in angstroms or nanometers
• 1 angstrom 10-10 m 10 nm. 

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MATHEMATICS CONCEPTS

• This course requires some mathematics, but this
  is not a math course.
• You may use a scientific calculator at any time.
  
• If you forgot how to work a specific function on
  the calculator, please ask the instructor, even
  in the middle of a quiz or exam.
• A simple, 4-function calculator is not sufficient
  on tests.

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To use the calculator

• you must have some basic knowledge of exponents.
• Most calculators will do these problems for you
  
• 2.9979 108 is entered as
• 2.9979 EE 8 or some variation of this depending
  on your specific calculator.

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The keys y x, x y, or

• raise numbers to any power, even weird powers.
• The bars in indicate a key on the calculator.
  

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Formulae for the

• manipulation of exponents that may be useful
  are         10x 10 y 10 x y         ax
  a y a x y         ax ? a y a x-
  y         1/ a y a y         ?(a) a
  ½         n?(am) a m/n 

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EXAMPLES

• 1.23 10 3 6.15 10 6
• 1.23 6.15 10 36
• 7.57 10 9.

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3?(12 2) 6?(12 5)

• 12 2/3 12 5/6
• 12 4/6 12 5/6
• 12 9/6
• 12 3/2 41.57 by calculator!
• 12 ( 3 ? 2 )
• to do this the easy way on the calculator you
  enter
• 12 ( 2 ? 3 ) 12 ( 5 ? 6
  )

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Astronomy is an adventure of the human mind
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Guiding Questions

• What methods do scientists use to expand our
  understanding of the universe?
• The scientific method hypothesis, model, theory.
• What makes up our solar system?
• The Sun, planets, moons, asteroids, meteoroids,
  comets, and dust.

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Guiding Questions

• What are stars? Do they last forever?
• The Sun is a star and stars are much like the
  Sun. Stars are born, exist, and die.
• What are galaxies? What do astronomers learn by
  studying them?
• Galaxies are HUGE collections of stars. Our
  galaxy is the Milky Way. We learn how the cosmos
  was created, is existing, and will die.

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Guiding Questions

• How does measuring angles help astronomers learn
  about objects in the sky?
• We learn how to find their positions.
• What is powers-of-ten notation, and why is it
  useful in astronomy?
• Numbers in astronomy are so huge, that powers of
  ten make them mentally more manageable.

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Guiding Questions

• 7.What math concepts are necessary?
• Basic algebra an ability to use a calculator.
• 8.Why do astronomers measure distances in
  astronomical units, light-years, and parsecs?
• To make the distances more manageable.
• 9.How does studying the cosmos help us on Earth?
• It is the greatest laboratory in the Universe.
  We can study many things that are impossible to
  study on Earth. Also, astronomy is beautiful.