Astronomy 101 The Solar System Tuesday, Thursday 2:30-3:45 pm Hasbrouck 20 Tom Burbine [e-mail]

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Astronomy 101The Solar SystemTuesday,
Thursday230-345 pmHasbrouck 20Tom
Burbinetomburbine_at_astro.umass.edu
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Course

• Course Website
• http//blogs.umass.edu/astron101-tburbine/
• Textbook
• Pathways to Astronomy (2nd Edition) by Stephen
  Schneider and Thomas Arny.
• You also will need a calculator.

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Office Hours

• Mine
• Tuesday, Thursday - 115-215pm
• Lederle Graduate Research Tower C 632
• Neil
• Tuesday, Thursday - 11 am-noon
• Lederle Graduate Research Tower B 619-O

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Homework

• We will use Spark
• https//spark.oit.umass.edu/webct/logonDisplay.dow
  ebct
• Homework will be due approximately twice a week

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Astronomy Information

• Astronomy Help Desk
• Mon-Thurs 7-9pm
• Hasbrouck 205
• The Observatory should be open on clear
  Thursdays
• Students should check the observatory website at
  http//www.astro.umass.edu/orchardhill for
  updated information
• There's a map to the observatory on the website.

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Final

• Monday 12/14
• 400 pm
• Hasbrouck 20

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HW 5

• There is a HW 5 replace which will replace your
  HW 5 score if you get a higher grade
• F G M1 M2
• r2
• G 6.67 x 10-11 m3/(kg?s2)

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HW 6

• Due today

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HW 7

• Due next Thursday

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Atoms make up molecules

• H2O - water
• CO2 carbon dioxide
• CH4 - methane

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Spectroscopy

• Spectroscopy is the study of the interaction
  between radiation and matter as a function of
  wavelength (?).
• You can use spectroscopy to determine what is in
  a body (planet, star, etc.) or atmosphere

http//upload.wikimedia.org/wikipedia/commons/f/f5
/Light_dispersion_conceptual_waves.gif
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• How did scientists recently determine that there
  was water on the Moon?

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Water on the Moon
Grey - H2O and OH absorptions
White line - NASA' Cassini spacecraft Blue line
- NASA's Moon Mineralogy Mapper instrument on the
Indian Chandrayaan-1 spacecraft
http//www.nasa.gov/images/content/388950main_ROGE
R_2-516.jpg
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Definitions

• Reflectance How much light an object reflects
• Absorption Light is absorbed and not reflected

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Light cause water molecules to vibrate

• http//www.btinternet.com/martin.chaplin/vibrat.h
  tml

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How much water?

• If you had a cubic meter of lunar soil, you could
  squeeze it and get out a liter of water
• Water has to be near the surface

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How do you use light to determine what is in an
astronomical body like a star?
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• http//www.youtube.com/watch?v9LrTeadnF6Q
• http//www.youtube.com/watch?vVY-bcMfLKeg

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What happens when electrons absorb energy?
http//www.meditech.cn/images/pic9.jpg
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http//library.thinkquest.org/C006669/media/Chem/i
mg/bohr.gif
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Energy levels where an electron can reside To go
to a higher energy level, an electron needs to
gain energy To go to a lower energy level, an
electron needs to lose energy
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eV

• 1 eV 1.6 x 10-19 Joules

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Rules

• An electron can not jump to a higher energy level
  unless it gains energy from somewhere else
• Absorbs a photon
• Gains kinetic energy from an impacting particle
• To go to a lower energy level, the electron must
  lose energy
• Emits a photon
• Electron jumps can occur only with the particular
  amounts of energy representing differences
  between possible energy levels

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Heated hydrogen gas Emission line spectrum
White light through cool hydrogen gas Absorption
line spectrum
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Types of spectra

• Emission radiation is emitted at characteristic
  wavelengths
• Material is hot so electrons keep on bumping
  into each other and transferring kinetic energy
  to each other so they jump between particular
  energy levels
• Absorption radiation is absorbed at
  characteristic wavelengths
• Radiation passes through the material

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http//www.astro.bas.bg/petrov/herter00_files/lec
07_04.jpg
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So why is this important

• Different elements have different number of
  electrons
• Different elements have different energy levels
  for their electrons

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So

• Different elements can absorb light at specific
  energies
• Different elements can emit light at specific
  energies
• So if you can measure the wavelength of the light
  from an astronomical body, you can determine
  whats in it

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Emission line spectra
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How can you determine velocities of objects?

• Doppler Shift The wavelength of light changes
  as the source moves towards or away from you
• Since you know the wavelength position of
  emission or absorption features
• If the positions of the features move in
  wavelength position, you know the source is moving

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So

• Source moving towards you, wavelength decreases
• blueshift
• Source moving away from you, wavelength increases
• redshift
• http//www.youtube.com/watch?v-t63xYSgmKE
• http//www.youtube.com/watch?va3RfULw7aAY

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nanometer

• 1 nanometer 1 x 10-9 meters

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Formulas for light

• vrad/c ?shift ?rest
• ?rest
• Rest wavelength of a line of hydrogen is at
  656.285 nm
• You observe this line at 656.255 nm for a star
• What is the velocity of this star?
• vrad/c (656.255 -656.285)/656.285 nm
• vrad/c -4.5712 x 10-5
• vrad -4.5712 x 10-5 3 x 108 m/s -13,700 m/s
  -13.7 km/s
• It is blue-shifted so the motion is toward us

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Blackbody

• A black body is an object that absorbs all
  electromagnetic radiation that falls onto it.
• Perfect emitter of radiation
• Radiates energy at every wavelength

http//www.daviddarling.info/images/blackbody.jpg
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• Stefan-Boltzman Law - energy radiated per unit
  surface area of a black body in unit time is
  directly proportional to the fourth power of the
  black bodys temperature
• Wiens Law - blackbody curve at any temperature
  has essentially the same shape as the curve at
  any other temperature, except that each
  wavelength is displaced, or moved over, on the
  graph

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• Stars and planets act can be modeled as
  blackbodies

http//www.astro.ncu.edu.tw/contents/faculty/wp_ch
en/Ast101/blackbody_curves.jpg
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Any Questions?