Physics

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Physics

• Keplers Three Laws of Planetary Motion
• asemi-major axis
• bsemi-minor axis
• eeccentricity
• Focus, Foci

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• Distance, Velocity from the Sun at any given
  time
• qangle from perihelion

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• Keplers second law rate of orbit changes (fast
  at perihelion, slow at aphelion)
• Keplers third law
• P2 k a3
• Newtons version (correct version)

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• Orbits arent that simple
• More terms needed
• a Semi major axis
• e - eccentricity
• i - inclination
• q perihelion distance
• W longitude of the ascending node
• w argument of the perihelion

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• Non-elliptical/circular orbits
• Depends upon velocity, direction
• Velocities lt Escape velocity elliptical/circular
  

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• Velocity Escape Velocity
• Orbit becomes parabolic
• e1, qclosest approach
• Velocity gt Escape Velocity
• Orbit is hyperbolic
• egt1

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Gravity

• Current formula two objects
• Three objects disaster!
• 3-body problems

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3-Body Effects

• Simplifications good!
• Perturbations
• Predicatable (periodic)
• Commensurable orientations (orbits)
• Beat Phenomena
• Ratios of orbits ½, 1/3, ¼, 2/3, 2/5, etc.
• Increases influence
• examples Asteroid belt, Planetary rings

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Lagrangian Points

• Gravitational Peaks Valleys associated with two
  objects.

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L1, L2, L3 Unstable L4, L5 Stable
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• Lagrangian Objects
• Jupiter Sun system
• Trojan Asteroids
• Earth Moon system
• Dust
• Earth Sun system
• L1 - SOHO
• L2 - WMAP, JWST
• L4, L5 mainly dust, satellites maybe

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• Mars Sun system
• L4, L5 - 6 asteroids
• Saturn Dione system
• L4, L5 - Helene, Polydeuces
• Saturn Tethys system
• L4, L5 - Calypso, Telesto
• Neptune - Sun system
• L4, L5 - about 6 asteroids

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Horseshoes Tadpoles

• Horseshoe orbits
• Not really how things move
• Matter of perspective
• Janus/Epimetheus

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Cruithne
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2002 AA29
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Tadpole Orbits

• Objects trapped in L4, L5 move around

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• Who controls all of this?
• The Sun?
• Not necessarily sphere of influence
• Hill Sphere distance where an object controls
  motion of other objects
• All satellites within each planets Hill sphere

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Tides

• Force that depends on object size/distance3
• Strong distance effect!
• Earth-Moon system
• High/Low tides
• Earths rotation
• Synchronous rotation of Moon (11)
• Moons migration away
• Sun contributes 20

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Killer Tides!

• Not really
• When do they hurt?
• When you get within the Roche Limit
• No precise limit
• Tensile strength (Composition, density, etc)

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• Tidal Heating
• Io, Europa, Ganymede
• Enceladus
• Triton

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Ring

• Resonances
• Perturbations

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Light/Gas Influences

• Does effect motion small objects mainly
• For sub-micron (10-7 m or less)
• Corpuscular drag
• Solar Winds particles from the Sun
• Gas drag
• Atmospheric effect

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• For micron sized ( 10-6 m)
• Radiation pressure
• Photons energy influence
• Fradradiation force
• Qcorrection factor
• aparticle size
• rdistance
• Lluminosity

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• For centimeter sized objects (0.01 m)
• Poynting-Robertson Drag
• Relativity effect
• Motion of particle effects re-emission of light
• Causes decreasing orbit
• Decaying orbits
• Particles that make up the Zodiacal light
• Need to be replenished!

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• For meter sized objects
• Yarkovsky (Yarkovski) effect
• Hot objects give off light
• When they give off light alters motion
• Influenced by temperature variation across it
• diurnal effects (rotation)
• seasonal effects
• albedo/composition variations
• Yarkovsky-O'Keefe-Radzievskii-Paddack effect
  (YORP)
• Irregular shape alters motion

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Light

• Other things you may have forgotten
• Types of light wavelength order
• Radio longest - lowest energy
• Microwave
• Infrared
• Visible (ROYGBIV)
• Ultraviolet
• X-ray
• Gamma-ray shortest - highest energy

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• clf
• Speed wavelength x frequency
• Wiens law for black bodies
• Peak type of light emitted - temperature
• lmax 0.0029/T
• Doppler effect
• Change of wavelength due to motion

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• Spectrum of planets
• Absorption due to atmosphere, surface material

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Element Spectra
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Albedo

• How light is absorbed reflected measured by the
  albedo
• Bond Albedo averaged over all wavelengths, all
  directions most commonly used
• Total reflected/total absorbed
• If it equals 0, what does that mean?
• If it equals 1, what does that mean?

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• Albedo effects temperature
• Light coming in primarily visible
• Light emitted primarily IR
• Difference of incoming/outgoing influences
  environment of object (Greenhouse effect)