Stars Galaxies and the Universe

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Stars Galaxies and the Universe

• Week 1
• Dr Bryce

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Class Policies

• This is a 3 or 4 semester hour class
• Meets 3 times a week MWF
• For 4 semester hour students there is an
  additional lab which meets once a week starting
  next week
• There will be 10 graded homework quizzes, 3
  in-class exams and a final exam

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Contacting your Instructor

• Office is 402 Van Allen Hall
• Close to the western elevator (Dubuque Street
  side)
• Office hours are Fridays 220-4pm
• Email hmbryce_at_gmail.com
• Drop/Add slips must go to the Physics general
  office 203 Van Allen Hall, the instructor cannot
  sign them for you

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Homework Quizzes

• 10 online quizzes will be made available on ICON
  as we progress through the semester
• Each quiz is graded and the total score will be
  used to calculate your grade
• Each quiz will have a time limit and deadline
• It is students responsibility to ensure that they
  have access to ICON in sufficient time
• Students are reminded that ICON can appear to
  run slowly at peak hours

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Textbook

• Astronomy Journey to the Cosmic frontier.
• 4th Edition
• Volume 2 Stars and Galaxies
• Chapters 1-6 and 16-25
• For lab students the materials will be provided
  online

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Exams

• 3 in-class one hour exam
• September 26th
• October 31st
• December 12th
• The final will take place on Tuesday December
  18th at 945am
• These dates are subject to change

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Exams continued

• Will be multiple choice
• Expect 25 questions in each class exam and 40 in
  the final exam
• The class exams will cover material in the 12 or
  so previous lectures, however the final will be
  cumulative
• Make up exams are available only in serious and
  documented cases, students are required to make a
  reasonable effort to contact the instructor prior
  to the exam that they will miss.

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Grading

• Letter bands will be announced later
• Plus and minus letter grading will be used
• Students with a final mark lower than 50 or who
  fail the lab section will fail the course overall
  
• Expect grade bands to fall at around 85, 70,
  60, 50.

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3 Semester hour students

• 25 for each class exam
• 25 for homework quiz total
• Lowest score will be dropped
• Plus 25 for final exam (which cannot be dropped)

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4 Semester hour (with lab) Students

• 18.75 for each class exam
• 18.75 for homework quiz total
• Lowest score will be dropped
• Plus 18.75 for final exam (which cannot be
  dropped)
• Plus 25 from Lab scores

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Tutorials

• Drop in tutorials are available
• http//www.physics.uiowa.edu/atutorial.html
• This is a great resource for your studies, you
  simply need to turn up and ask away!

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Calculators

• You will need a calculator for this course
• As we will be dealing some very large and some
  very small numbers, scientific function EE is a
  must.
• Also useful, square root, sin, cos and tan
• Cheap calculators are typically easier to operate
  than expensive overly complicated models.

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General Comments

• It is our aim to provide an atmosphere in which
  the majority of students can feel comfortable and
  can focus on learning
• With that in mind please switch off cell phones
  when entering the lecture theatre
• Please refrain from any behaviour that will
  disrupt your classmates learning environment, ie
  eating, audible conversation, newspaper shuffling
  etc
• Students whose behaviour is not deemed
  appropriate will be asked to leave the classroom

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Further General comments

• Students are reminded that CLAS guidelines
  suggest 2 hours of out of class study per week
  for every semester hour allotted to a class.
• If you may require a modification of seating,
  testing or any other aspect of the teaching and
  learning environment please contact the
  instructor.

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Aims of this class

• Understand and follow (with interest!)
  developments in Astronomy throughout your life.
• Many sources for interesting Astronomy News
• To understand these reports and their
  significance we need to develop our vocabulary,
  understand what is already known (distances,
  masses, temperature), know what models are
  currently being used.

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Tonight in Astronomy

• Or rather early tomorrow morning
• Before sunrise/dawn on Tuesday 28th there will be
  a lunar eclipse
• This occurs when the Moon passes through the
  Earths shadow
• The eclipse will begin just before 4am
• http//www.skyandtelescope.com/community/skyblog/o
  bservingblog/9282371.html

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Science

• The intellectual and practical activity
  encompassing the systematic study of the
  structure and behaviour of the physical and
  natural world through observation and
  experimentation.
• A systematically organized body of knowledge on
  any subject.

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Astronomy

• The branch of science which deals with celestial
  objects, space, and the physical universe as a
  whole
• Observation rather than experimentation
• Astrophysics concerned with the physical
  nature of stars and other celestial objects and
  the application of the laws and theories of
  physics to the interpretation of astronomical
  observations

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Scientific Theory

• Scientific theories are designed to be tested
• A theory that cannot be tested (even at a point
  in the future) is poorly thought out.
• Accepted theories have been subjected to many
  tests and we sometimes use the word law, eg Law
  of Gravitation.
• A theory can only be proved wrong, not right.
• Theories explain real life!
• Not to be confused with belief or faith.

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Scientific Method
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Science
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Bad Science

• Disregards observations at whim
• Disregards known laws at whim
• Not testable
• See Astrology
• See www.badastronomy.com for a lighthearted look
  at mistakes in movies, television and popular
  culture.

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SI Units

• In 1960, the Eleventh General Conference on
  Weights and Measures was held in Paris and Le
  Systeme International d'Unites was adopted.
• This International System, or SI, as it is
  commonly referred to, is used for commerce and
  Science around the world. 
• There are seven SI base units.  
• Everything that is measurable, can be measured by
  these base units, or by units derived from these
  bases. 

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SI units

• For length we will use the meter (m)
• Not yards, feet, inches
• In astronomy we will use 3 other units for
  distance, depending on the scale we are
  observing
• For time we will use the second (s)
• For mass we will use the kilogram (kg)
• Not the pound

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The Kelvin temperature scale

• In everyday life you are probably pretty
  comfortable using the Fahrenheit temperature
  scale.
• The rest of the world used Celsius or Centigrade
  for everyday measurements. 100 degrees between
  freezing and boiling points of water

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Kelvin temperature scale

• Absolute zero is 0 Kelvin
• Absolute zero is the point at which atoms would
  have zero kinetic energy
• Only positive temperatures using Kelvins

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Temperature conversions

• Kelvin Celsius 273
• Celsius Kelvin 273
• Fahrenheit (Celsius9/5) 32
• Celsius (Fahrenheit -32)5/9

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Powers of ten

• Astronomers use powers of ten to write numbers in
  more convenient forms.
• Just as we say million instead of 1 zero zero
  zero zero zero zero
• It is important to remember
• Negative powers mean small numbers
• Positive powers mean large numbers

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Example

• 3.0108
• 3.0 is the coefficient, which must be greater
  than or equal to 1 but less than 10
• 10 is the base
• 8 is the exponent, which shows the number of
  decimal places that the decimal point needs to be
  moved to change the number to standard notation. 
  A negative exponent means that the decimal point
  is moved to the left when changing to standard
  notation and a positive exponent means moved to
  the right.
• When you multiply numbers with scientific
  notation, multiply the coefficients together and
  add the exponents.  The base will remain 10.

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Frequently used Powers

• Nano 10-9
• Micro 10-6
• Kilo 103
• Mega 106
• 1 10-9 Instead of 0.000000001
• 210-6 0.000002
• 5103 5000
• 3.2106 3200000

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Basic Observations

• Each Evening the Sun sets, the skies darken and
  on clear nights we are able to see stars/planets.
• We can also easily observe the westward motion of
  these heavenly/celestial bodies

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Defining Location

• In order to observe celestial bodies we need to
  find a way to define their position.
• We are familiar with using coordinates on Earth

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Latitude/Longitude
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Latitude/Longitude

• There has to be defined positions that other
  locations are found from.
• For example the Earths equator which divides
  the Earth into Northern and Southern hemispheres.
  Latitude is measured north or south of the
  equator.
• Longitude is measured east or west of the
  Greenwich meridian (also known as the prime
  meridian)

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The Celestial Sphere
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Measuring the Sky

• A circle is divided into 360 degrees
• So the hemisphere of the sky is 180 degrees
  across
• But a degree covers a large span of Sky

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Measuring the Sky

• For example the Moon is 0.5o across
• So we need to divide degrees into smaller angles
• We use minutes of arc
• One minute of arc 1/60 of a degree

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Even smaller

• And each minute of arc is divided further into
  seconds
• One second of arc 1/60 of a minute of arc
• One second of arc 1/3600 of a degree
• The angular size of a penny at 4km (2.5 miles)

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The Horizon system
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The horizon system

• The zenith is the point directly above your head
• Altitude is the angular distance above the
  horizon, the zenith is at an altitude of 90o, the
  horizon is 0o (latitude)
• Azimuth is the angular distance measured east
  from north, north is 0o, east 90o, south is 180o,
  west is 270o (longitude)

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The problem is.

• That over the course of a night, both the
  altitude and azimuth of stars change
• Recording these numbers isnt going to be that
  helpful for a future observation

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The rotation of the Celestial Sphere