Review for Test 1

1
Review for Test 1

• 2-27-2007

2
The Lectures

• 1. Review of the syllabus.
• 2. Where we are planetary motion, eclipses.
• 3. The Sun nuclear energy, solar activity.
• 4. The planets, density, atmospheres,
  spectroscopy.
  
• 5. Telescopes, spectral windows, albedos.
• 6. Solar System Formation
• 7 8. Meteorites classifications, radio-isotope
  dating
  
• 9. Asteroids
• 10. Comets

3
Lecture 2 History etc.

• The ecliptic path of the Sun through the sky,
  and the location of the zodiac
  
• The seasons equinoxes and solstices.
• Phases of the Moon, what causes them, eclipses.
• Aristotles geocentric universe.
• Retrograde motion of the planets.
• Copernican revolution, heliocentrism.

4
Lecture 2. Laws of motion

• Keplers Laws of planetary motion
• 1. Law of Orbits Each planet moves in an
  elliptical orbit about the Sun, with the Sun at
  one focus of the ellipse.
  
• 2. Law of Areas A planet sweeps out equal areas
  in equal time during its orbit.
  
• 3. Law of Periods The cube of the distance
  divided by the square of the period is a
  constant.
  
• P2 a3
• Galileos discoveries
• Newtons understanding of gravity
• Escape and orbital velocity

http//www.eso.org/outreach/eduoff/edu-prog/catcha
star/casreports-2004/rep-070/
5
Lecture 3-The Sun

• Parallax, Temperature Scales
• Matter
• Atoms vs. elements
• Isotopes vs. ions
• The nucleus, protons, neutrons and electrons
• Hydrogen vs. Helium
• Molecules and compounds
• Radiation, light, waves and particles, speed of
  light, the EM spectrum
  
• Parts of the Sun
• Core Where fusion occurs, T 15 million K,
  Energy released as Gamma Rays
  
• Radiation Zone Outside the core, gamma rays are
  absorbed and reemitted constantly
  
• Convection Zone Above the radiation zone, below
  the visible surface, energy is transported via
  convection, similar to a rolling water in a
  boiling pot.
• Photosphere visible surface, 5800 K
• Chromosphere Above the photosphere, looks pink
  during eclipses
  
• Corons Very hot layer of ionized gas, 4 million
  K, is the beginning of the Solar Wind.

6
Lecture 3- The Sun

• The Sun uses 4 million tons of matter per second,
  fusing H to He.
  
• E mc2 relates how much energy is created when
  mass is lost in nuclear reactions.
  
• Solar activity
• Sunspots cool dark patches on the surface caused
  by material trapped in magnetic fields.
  
• Flares eruptions from the surface associated
  with breaking of magnetic field lines.
  
• CMEs Huge ejections of matter from the Corona.

7
Lecture 4- The planets

• Sizes and densities
• Terrestrial Mercury, Venus, Earth and Mars
• Giant Jupiter, Saturn, Uranus, and Neptune.
• Icy/KBO/other Pluto, Eris, and other KBOs.
• Hints on composition
• Mercury has a higher density than we might
  expect.
  
• Giant planets have very low densities
• Clearly the planets must have different
  compositions.

8
Lecture 4 Forms of matter

• Rocks
• Igneous (e.g. basalt)
• Sedimentary (e.g. limestone)
• Metamorhpic (e.g. marble)
• Gas Atmospheres can be acquired
• Direct Capture from the original Solar Nebula
  (primary)
  
• Outgassed from rocks after differentiation
  (secondary)
  
• From cometary impacts (secondary)
• How to lose your atmosphere?
• Thermal escape the energy of the gas is too
  great and velocities grow larger than escape
  velocity
  
• Impacts comets or asteroid blow the atmosphere
  away
  
• Solar Wind The fast-moving Solar Wind blows the
  atmosphere away
  

9
Lecture 5 Telescopes etc.

• Astronomers have two options to study distant
  bodies
  
• In situ investigations directly studying the
  object,
  
• Mars rovers,
• Galileo atmosphere probe.
• Remote sensing studying the radiation emitted or
  reflected from a distant body,
  
• Earth-based telescopes,
• Spacecraft orbiting Earth, or other planets.
• Planets are cooler than the Sun, and cooler
  objects are redder (Wiens law).
  
• Because of this planets emit thermal radiation at
  Infrared wavelengths (IR), instead of visible
  like the Sun.
  
• The wavelengths that we can observe at are called
  atmospheric, or spectral windows

10
Lecture 5 Telescopes

• Planets also dont reflect perfectly. How much
  light they do reflect is called its albedo.
  
• Moon 0.11
• Venus 0.75
• Average KBO or asteroid 0.04 0.15
• How much does size matter?
• Collecting area increases (proportional to D2)
• Spatial resolution (proportional to D)
• Working by way of the photoelectric effect, CCDs
  are grids of pixels, which convert photons into
  electric charges.
  

11
Lecture 6 Solar System Formation

• Facts we can use to figure stuff out
  Composition
  
• The sun is almost all H and He, therefore the
  solar nebula was mostly this also.
  
• The inner planets dont have a lot of volatiles.
• More facts orbits and rotations
• Planets orbit in the same plane, mostly
• Planets orbit in same direction.
• Sun rotates in the same direction

12

• Angular momentum is the product of three
  quantities mass, size (radius) and rotation
  speed (or velocity)
  
• L mrv

Figure Universities Corp. For Atmospheric
Research (UCAR)
13
The disk/planet formation

• The central parts of the nebula were very hot
  over 10,000 K.
  
• Going outwards in the nebula, the temperature
  drops, and different compounds condense out at
  different distances from the protostar
  
• Calcium, Aluminum oxides first,
• then Iron-Nickel alloys (by 0.2 AU, Mercury),
• Magnesium silicates and oxides next (by 1.0 AU),
• Olivine and Pyroxene (Fe-Si-O compounds),
• Feldspars (K-Fe-Si-O compounds),
• Hydrous silicates,
• Sulfates,
• And finally ices (water ice by 5.0 AU).
• This radial variation in composition in the
  nebula is one cause of the variation in
  composition of the planets with solar orbit
  distance.

14
Lecture 7 Meteorites

• Major mineralogical types Stony, Iron,
  Stony/Irons
  
• Origins Primitive (chondrite), Differentiated
  (achondrite), Breccias
  
• Primitives are all stones, carbonaceous or other
  kinds.
  
• Differentiated can be any mineralogical type.
• Breccias are usually crustal material from
  asteroids or planets, could be primitive or
  differentiated.
  
• Falls and Finds.
• We FIND mostly irons and stony-irons.

15
Lecture 7 Meteorites

• The few orbits we have for meteorites all suggest
  Main Belt origins
  
• Primitives are old (4.5 Gyr), have chondrules,
  some iron, and are often breccias.
  
• Carbonaceous Chondrites are a type of primitive
  stone, which are less dense and show signs of
  volatiles and carbon.
  
• Two big meteorites, Tagish Lake and Murchison are
  C.C. which contain amino acids

16
Lecture 8 Differentiated

• Differentiated meteorites lack chondrites, and
  are called achondrites.
  
• Irons have up to about 10 nickel, and have a
  crazy pattern, widmanstatten, due to slow
  cooling.
  
• These meteorites from the differentiated
  bodies
  
• Stony/Irons, also come from differentiated
  bodies, probably the boundary between core and
  crust.
  
• Stony Irons are dated to about 4.4 or 4.5 Gyr
  years, slightly younger than primitives.
  
• Eucrites have been found to come from the crust
  of the asteroid Vesta
  
• Basalts are lighter rocks, from asteroid crusts.
  Some have been found to come from Mars or the
  Moon.

17
Lecture 8 radioactivity

• Two main types,
• Alpha Decay The emmited particle is a helium
  nucleus 2 protons and 2 neutrons.
  
• Beta Decay The emitted particle is either an
  electron or positron. This particle is emitted
  from the nucleus, no the swarm of electrons
  around the nucleus.

18
Lecture 8 Dating rocks.

• When we have a closed system, or a system is no
  longer having its isotopes modified. Then we can
  track the amount of
  
• Parent nucleus (original isotope) as it
  decreases,
  
• Daughter nucleus (newly created after decay) as
  it increases.
  
• We need to know the following things for dating.
• The current parent/daughter isotope ratio
• The original parent/daughter isotope ratio
• The rate of decay.

19
Lecture 9 Asteroids

• The number of asteroid follows 1/D2 instead of
  1/D3. This means we can estimate the total
  mass.
  
• The Moon is 20 time more massive than all the
  asteroids.
  
• Orbits and rotations are easily measured, sizes
  are not,
  
• Occultations, get size by watching it eclipse a
  star
  
• Spectroscopy, use reflection and emission at
  different wavelengths to estimate size.

20
Lecture 9 asteroid orbits

• They live between 2.2 and 3.3 AU.
• The gaps in the asteroid belt, are caused by
  resonances with Jupiters orbit.
  
• There are safe resonances with Jupiter, like 11,
  which is what the Trojans are on.
  
• Asteroid families have similar orbits and
  spectra, suggesting they are collisional remnants
  of one large parent body.

21
Lecture 9 asteroids

• Asteroid types
• C-type carbonaceous, dark, with water,
  primitive
  
• S-type Stony, with silicates primitive
• M-type metallic, brighter differentiated
• S-type are in the inner Main Belt, C-type are in
  the outer MB, and are more numerous (75)
  
• Densities are all over the place due to porosity

22
Lecture 9 asteroids

• WE also find asteroids
• At Jupiters lagrange points, the Trojans
• Near Earth, NEAs
• Out around the Giant planets, Centaurs
• The more distant, the redder they appear.
• Asteroids we have gone to
• Gaspra, by galileo, flyby, irregular shape
• Ida, found a small moon, lots of craters
• Mathilde, huge crater, low porosity
• Eros, orbited and landed, missing craters and
  moving dust.
  
• Itokawa, orbited and landed, rubble pile