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Linking Asteroids and Meteorites through Reflectance Spectroscopy_1_

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					Astronomy/Geology 110
  Tuesday, Thursday
     2:40-4:00 pm
     Carnegie 204

      Tom Burbine
   tburbine@bates.edu
                          Course
• Course Website:
  – http://abacus.bates.edu/~tburbine/ATGE110/
  – Also on Lyceum.bates.edu
• Textbook:
  – Moon and Planets (5th Edition) by William K. Hartmann
• You also will need a calculator.
                  Office Hours
•   Tuesday 1:30-2:30 pm
•   Thursday 11 am-noon
•   Carnegie 204
•   I will also be having lunch at the Commons every
    Thursday from noon-1 pm
              Help Sessions
• Monday and Wednesdays at 4 pm in Carnegie 215
               Quiz Average
• Quiz Average was an 86
• Grades ranged from a 52 to a 100
            HW #4 (due today)
• Choose a planetary science book to read
• Submit the title of the book and the author
• Write a short paragraph on why you chose this
  book
• You will give a book report during one of your
  last two lab periods on the book
         HW #5 (due Thursday)
• Energy problems
        HW #6 (due September 25)
• You need to interview and film a number of people and
  ask them a planetary science question that they should
  know the answer. The video should be about a minute
  long. The end of the video should include the answer.
• Make a video as a team of two or three (or by yourself if
  you don't want a partner).
• Cameras can be obtained at the Digital Media Center 121
  Pettigrew.
• Macs are available at the Digital Media Center for editing
  the video and burning the video to a disk.
• Submit the file to me on September 25. The file should
  have your names or name in the title.
       HW #7 (due next Tuesday)
• Star problems
A Maybe Planet, Orbiting Its Maybe Sun
                       7 to 12 times as massive as Jupiter




  star is 85% as massive as the Sun, but less than 0.1% its age
                                           near-infrared image
http://www.nytimes.com/2008/09/18/science/space/18planet.html
                           5 th    Dwarf Planet
  • 5th dwarf planet Haumea and its two moons
    Hi'iaka and Namaka,
  • Named after the Hawaiian fertility goddess
  • Moons after the patron goddess of Hawaii and a
    water spirit.




http://en.wikipedia.org/wiki/Image:2003EL61art.jpg   1/3 the mass of Pluto
                       Matter
• Matter is material
                      Energy
• Energy is what makes matter move
• In English Units, we use calories to measure
  energy
• In science (and in this class), we will use joules to
  measure energy
       3 basic categories of energy
• Kinetic energy – energy of motion
• Potential energy – energy being stored for
  possible conversion into kinetic energy
• Radiative energy – energy carried by light
                  Kinetic energy
•   Kinetic energy = ½ mv2
•   m is mass in kg
•   v is velocity in meters/s
•   A joule has units of kg-m2/s2
• How much energy does a 2 kg rock have if it is
  thrown at 20 m/s?
• Kinetic energy = ½ mv2
• A) 200 J
• B) 400 J
• C) 40 J
• D) 800 J
                    Answer
• KE = ½ * 2 * (20) *(20) = 400 joules
               Thermal energy
• Temperature – average kinetic energy of particles
• Higher temperature – more kinetic energy,
  particles moving faster
• For examples, air molecules around you are
  moving at ~500 m/s
              Temperature scales
•   In America, we use Fahrenheit
•   Water freezes at 32 degrees F
•   Water boils at 212 degrees F
•   Everywhere else, they use Celsius
•   Water freezes at 0 degrees C
•   Water boils at 100 degrees C
                  In Science
• Temperature is measured in Kelvin
• Zero Kelvin is absolute zero – nothing moves
• Add 273.15 to the Celsius temperature to get the
  Kelvin temperature
• 273.15 Kelvin = 0 degrees Celsius
     Gravitational Potential Energy
• Gravitational Potential Energy released as an
  object falls depends on its mass, the strength of
  gravity, and the distance it falls
• For example, your gravitational potential energy
  increases as you go farther up in the air
• This is because you hit the ground at a faster
  speed if you jump from a higher distance
       Converting Mass to Energy


• What is the most famous formula in the world?
                     E = mc2

•   m is mass in kilograms
•   c is speed of light in meters/s
•   So E is in joules
•   very small amounts of mass may be converted
    into a very large amount of energy and
Who came up with it?
• How much energy can be produced if you can
  convert 10 kg of material in energy?
• E = mc2
• A) 3.0 x 108 J
• B) 3.0 x 1016 J
• C) 9.0 x 1017 J
• D) 9.0 x 1010 J
                       Answer
•   E = 10 kg * (3 x 108 m/s) * (3 x 108 m/s)
•   E = 10* (9 x 1016) J
•   E = 90 x 1016 J
•   E = 9.0 x 1017 J
                Mass-Energy
• So Mass is a form of potential energy
• Where is one place where you see mass converted
  into energy?
                       Atoms
•   Atoms are made up of 3 types of particles
•   Protons – positive charge (+1)
•   Electrons – negative charge (-1)
•   Neutrons – neutral charge (no charge)
•   Protons and Neutrons are found in the nucleus
                    Elements
• Different elements have different numbers of
  protons
• The properties of an atom are a function of the
  electrical charge of its nucleus
                     Charge
• If an atom has the same number of electrons and
  protons, it has a neutral charge
• More electrons than protons, negatively charged
• More protons than electrons, positive charged
• Neutrons have neutral charge so don’t affect the
  charge of an atom
                           Definitions
• Atomic Number – Number of protons
• Atomic Mass – Number of protons and neutrons
• U235 – atomic mass
    92- atomic number

• usually 92 not written
• Isotopes – Same number of protons but different
  numbers of neutrons
           First nuclear weapons
• Worked by nuclear fission
• Use Uranium-235
• If a free neutron runs into a U-235 nucleus, the
  nucleus will absorb the neutron without
  hesitation, become unstable and split immediately
• The energy released by a single fission is due to
  the fact that the fission products and the neutrons,
  together, weigh less than the original U-235 atom
         Atoms make up molecules
•   H2O
•   CO2
•   CH4
•   Atoms made up with 2 or more different atoms
    are called compounds
               Star Formation
• How do we know that stars are continually
  forming?
Age of Solar System versus the Universe

• Solar System has an age of ~4.6 billion years
• Universe has an age of ~13.7 billion years
• All stars did not form at the beginning
              Astrophysical Analyses
               of the ages of Stars

• The Sun has an estimated lifetime of ~10 billion years
• Some stars have estimated lifetimes of ~10 million years
           Discovery of apparent
           star-forming regions
• Discovery of regions where stars surrounded by
  clouds of hydrogen gas and dust
Eagle Nebula (“Pillars of Creation”)

                                     young open cluster of stars

                                   region of hydrogen gas and dust

                                   The tower is 9.5 light-years high,
                                   about twice the distance from
                                   our Sun to the next nearest star.



                                   Hubble image

 http://en.wikipedia.org/wiki/Image:Eagle_nebula_pillars.jpg
                  Molecular Cloud
• A star-forming cloud is called a molecular cloud because
  low temperatures allow Hydrogen to form Hydrogen
  molecules (H2)
• Temperatures like 10-30 K
• Denser than surrounding regions
• The clouds can reach tens of light years in diameter and
  have an average density of 10²–10³ particles per cubic
  centimeter
   – The average density in the vacuum of space in our solar system
     is one particle per cubic centimeter
        Triggered Star Formation
• In triggered star formation, one of several events
  (e.g., supernova explosion) might occur to
  compress a molecular cloud and initiate its
  gravitational collapse.
• As a region gets denser, its gravity gets higher
• http://coolcosmos.ipac.caltech.edu/resources/infor
  mal_education/movies/SNR-VGA.mov
                       Or
• A region might be dense enough to collapse on its
  own
                  Condensing
• Molecular clouds tends to be lumpy
• These lumps tend to condense into stars
• That is why stars tend to be found in clusters
                   Protostar
• The dense cloud fragment gets hotter as it
  contracts
• The cloud becomes denser and radiation cannot
  escape
• The thermal pressure and gas temperature start to
  rise and rise
• The dense cloud fragment becomes a protostar
When does a protostar become a star
• When the core temperatures reaches 10 million K,
  hydrogen fusion can start occurring
        Things you need to know
• Fusion rate increases with increasing temperature
• There is a relation between thermal pressure and
  gravity
           Classification of Stars
• Stars are classified according to luminosity and
  surface temperature
• Luminosity is the amount of power it radiates into
  space
• Surface temperature is the temperature of the
  surface
     Luminosity-Distance Formula
• Apparent brightness = Luminosity
                      4 x (distance)2

Usually use units of Solar Luminosity
LSun = 3.8 x 1026 Watts
      Measuring Distance to Stars
• Measuring distances to stars is much harder to
  measure than brightness
• But to determine the Luminosity of the star, we
  need to know the distance to it
                 Wien’s Law
• Inverse relationship between the wavelength of
  the peak of the emission of a black body and its
  temperature
• λ = 0.00290/T
• λ is in meters
• T is in Kelvin
One nanometer = 1 x 10-9 m
           Surface Temperature
• Determine surface temperature by determining the
  wavelength where a star emits the maximum
  amount of radiation
• Surface temperature does not vary according to
  distance so easier to measure
1913
         Who were these people?
• These were the women (called computers) who
  recorded, classified, and catalogued stellar spectra
• Willamina Fleming (1857-1911) classified stellar
  spectra according to the strength of their hydrogen
  lines
• Classified over 10,000 stars
           Fleming’s classification
•   A - strongest hydrogen emission lines
•   B - slighter weaker emission lines
•   C, D, E, … L, M, N
•   O - weakest hydrogen lines emission lines
   Annie Jump Cannon (1863-1941)
• Cannon reordered the classification sequence by
  temperature and tossed out most of the classes
• She devised OBAFGKM
             More information
• Each spectral type had 10 subclasses
• e.g., A0, A1, A2, … A9 in the order from the
  hottest to the coolest
• Cannon classified over 400,000 stars
                OBAFGKM
• Oh Be A Fine Girl/Gal Kiss Me
• Play song
• http://www.mtholyoke.edu/courses/tburbine/AST
  R223/OBAFGKM.mp3
 Cecilia Payne-Gaposchkin (1900-1979)

• Payne argued that the great variation in stellar
  absorption lines was due to differing amounts of
  ionization (due to differing temperatures), not
  different abundances of elements
 Cecilia Payne-Gaposchkin (1900-1979)

• She proposed that most stars were made up of
  Hydrogen and Helium
• Her 1925 PhD Harvard thesis on these topics was
  voted best Astronomy thesis of the 20th century
     Hertzsprung-Russell Diagram
• Both plotted spectral type (temperature) versus
  stellar luminosity
• Saw trends in the plots
• Did not plot randomly
                  Remember
• Temperature on x-axis (vertical) does from higher
  to lower temperature
• O – hottest
• M - coldest
     Hertzsprung-Russell Diagram
• Most stars fall along the main sequence
• Stars at the top above the main sequence are
  called Supergiants
• Stars between the Supergiants and main sequence
  are called Giants
• Stars below the Main Sequence are called White
  Dwarfs
wd   white dwarfs
               Classifications
• Sun is a G2 V
• Betelgeuse is a M2 I
                      Radius
• Smallest stars on the main sequence fall on the
  bottom right
• Largest stars on main sequence fall on the top left
• At the same size, hotter stars are more luminous
  than cooler ones
• At the same temperature, larger stars are more
  luminous than smaller ones
           Main Sequence Stars
• Fuse Hydrogen into Helium for energy
• On main sequence, mass tends to decrease with
  decreasing temperature
• Two fusion reactions;
  – Proton-proton dominates – Sun’s mass or less
  – CNO cycle dominates – More massive than Sun
• http://www.astronomynotes.com/starsun/s3.htm
• http://www.astro.ubc.ca/~scharein/a311/Sim/fusio
  n/Fusion.html
                             Positron-positively charged
                                      electron
2 protons fuse
together
Forms proton and neutron
(deuterium- Hydrogen
isotope)
Positron given off
and destroyed by colliding
with electron
2 gamma rays given off
                                 Figure 15.7
Neutrino given off
proton fuses with deuterium
Forms Helium-3
Gamma ray given off
                           Figure 15.7
                     Collision of two Helium-3
                     nucleus
                     Produces Helium-4 nucleus
                     and 2 protons




Steps 1 and 2 must
occur twice

                       Figure 15.7
     Proton-Proton Chain Reaction
• Takes an average of 109 years to complete at the
  temperature of the Sun’s core
  – A hydrogen nucleus waits on the average 1 billion
    years before it undergoes an interaction with another
    hydrogen nucleus to initiate the sequence
• It if occurred faster, Sun would run out of fuel
                      Neutrinos
• Neutrinos (ν) – almost massless particles
• No charge
• Originally postulated to preserve conservation of energy,
  conservation of momentum, and conservation of angular
  momentum in beta decay (neutron decays into a proton)
   energy + p+ → n0 + e+ + νe
• It takes a neutrino about 2 seconds to exit the Sun
• More than 50 trillion solar electron neutrinos pass
  through the human body every second
CNO cycle




   www.nobelprize.org
What was the solar neutrino problem?
• A) More neutrinos appeared to be produced from
  the Sun than expected from models
• B) Less neutrinos appeared to be produced from
  the Sun than expected from models
• C) Neutrinos are dangerous to humans
• D) Neutrinos interfere with the fusion of
  hydrogen into helium
• E) Neutrinos turn helium into Lithium
 What is the solar neutrino problem?
• A) More neutrinos appear to be produced from
  the Sun than expected from models
• B) Less neutrinos appear to be produced from the
  Sun than expected from models
• C) Neutrinos are dangerous to humans
• D) Neutrinos interfere with the fusion of
  hydrogen into helium
• E) Neutrinos turn Helium into Lithium
How was the Homestake Gold Mine used
         to detect neutrinos?
• A 400,000 liter vat of chlorine-containing
  cleaning fluid was placed in the Homestake gold
  mine
• Every so often Chlorine would capture a neutrino
  and turn into radioactive argon
• Modelers predict 1 reaction per day
• Experiments found 1 reaction every 3 days
     How was the problem solved?
• Neutrinos can change from the type that had been
  expected to be produced in the sun's interior into
  two types that would not be caught by the
  detectors in use at the time.
• How much longer will it take the Sun to use up all
  its “fuel”?
• When the Sun uses up its fuel it will start
  expanding, which will be bad for people living on
  Earth
        Things you need to know

• Energy source for sun is four hydrogen atoms
  combining to produce one helium atom
• about 0.7% of the original mass is turned into
  energy during this process
• 10% of the Sun’s mass is hot (~8 million Kelvin
  or above) enough to undergo fusion
• Mass of the Sun = 2 x 1030 kg
                      And
• Total lifetime = (energy available)
    (rate [energy/time] at which sun emits energy)

• rate [energy/time] at which the Sun emits energy
  is equal to 3.8 x 1026 Watts (Joules/second)
                       And
• Time left = Lifetime – current age
• Current age = ~5 billion years
                     Calculation
•   Mass of the Sun that is turned into energy
•   m = 2 x 1030 kg * 10% * 0.7%
•   m = 1.4 x 1027 kg of Sun can be turned into energy
•   E = mc2
•   E = 1.4 x 1027 kg times 9 x 1016 m2/s2
•   E = 1.26 x 1044 Joules
                       Calculation
•   Lifetime = 1.26 x 1044 Joules/3.8 x 1026 Joules/second
•   Lifetime = 3.3 x 1017 seconds
•   Lifetime = 1.05 x 1010 years
•   Time left = 10.5 billion years – 5 billion years
•   Time left = 5.5 billion years
                      Fusion
• The rate of nuclear fusion is a function of
  temperature
• Hotter temperature – higher fusion rate
• Lower temperature – lower fusion rate
• If the Sun gets hotter or colder, it may not be good
  for life on Earth
   What is happening to the amount of
           Helium in the Sun?
• A) Its increasing
• B) its decreasing
• C) Its staying the same
   What is happening to the amount of
           Helium in the Sun?
• A) Its increasing
• B) its decreasing
• C) Its staying the same
So how does the Sun stay relatively
     constant in Luminosity
         (power output)
Figure 15.8
Figure 15.4
                 Parts of Sun
                     Core
• Core – 15 million Kelvin – where fusion occurs
Figure 15.4
               Radiation zone
• Radiation zone – region where energy is
  transported primarily by radiative diffusion
• Radiative diffusion is the slow, outward migration
  of photons
Figure 15.13
  Photons emitted from Fusion reactions

• Photons are originally gamma rays
• Tend to lose energy as they bounce around
• Photons emitted by surface tend to be visible
  photons
• Takes about a million years for the energy
  produced by fusion to reach the surface
Figure 15.4
                Convection Zone
•   Temperature is about 2 million Kelvin
•   Photons tend to be absorbed by the solar plasma
•   Plasma is a gas of ions and electrons
•   Hotter plasma tends to rise
•   Cooler plasma tends to sink
Figure 15.14
Granulation – bubbling pattern due to convection
bright – hot gas, dark – cool gas




                        Figure 15.14
Figure 15.10
Figure 15.4
                 Photosphere
• Photosphere is the solar surface
• Where photons escape into space
                   Sunspots
• Sunspots are on the photosphere
• Have temperatures of ~4,000 K
• Photosphere is 5,800 K
                    Sunspots
• Sunspots are regions of intense magnetic activity
• Charged particles tend to follow magnetic field
  lines
Figure 15.17
                   Sunspot Cycle




                            Figure 15.21

The cycle has a period of approximately 11 years, but the interval
between maxima can be as short as 7 years and as long as 15 years.
            Maunder Minimum
• Between 1645 and 1715, the sunspot activity
  virtually stopped
• Identified by E. W. Maunder from historical
  sunspot records
Figure 15.4
            Atmosphere of the Sun
• Chromosphere – above the photosphere and below the
  corona
• Temperature is about 10,000 Kelvin
• Most of the Sun’s ultraviolet light is emitted from this
  region
See Corona during eclipse
            Atmosphere of the Sun
• Corona – tenuous uppermost layer of the Sun’s
  atmosphere
• Temperature is about 1 million Kelvin
• Most of the Sun’s X-rays are emitted from this region
                     Corona
• Extends millions of kilometers into space
• Why its so hot is unknown
• Sun's corona is constantly being lost as solar
  wind.
Any Questions?

				
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