Solar System 2019 - UD Physics

Solar System 2019 - UD Physics
Solar System 2019
       Earth’s moon and other rocky
        bodies of our solar system
    Scott Jackson, Mt. Cuba Astronomical
       Observatory (and Planetarium)
Help session:
Sunday afternoon: March 3, 2019 at Mt Cuba
Test on March 16, 2019
“Two 8.5 x 11 inch two sided sheet”
Test will include questions about a series of
images projected onto the front of the room.    1
Solar System 2019 - UD Physics
Solar System 2019 - UD Physics
   demonstrate an understanding and knowledge of the geologic
    characteristics and evolution of the Earth’s moon and other rocky
    bodies of the solar system
      DwarfPlanets: Pluto, Ceres, Haumea, Makemake, Eris .
      Satellites: Earth’s Moon,Charon, Mimas, Phoebe
      General Details of Other Small Bodies: Asteroid Belt,Centaurs, Trojans,
       Trans-Neptunian Objects
      Specific Details of: ‘Oumuamua and (225088) 2007 OR10
      Missions: New Horizons, Dawn, Cassini, Lucy, Voyager 2
   History and formation processes
   Remote sensing, imagery and satellite measurements
   Kepler’s laws, gravitational effects of the moon and tides
   Rotation, libration, phases, and eclipses
   Surface Dating, volcanism & weathering, cratering & impact
   Internal, surface, and Atmospheric compositions
Solar System 2019 - UD Physics
Our sun’s evolutionary stages
• Gas and dust compress under self gravitation
   • Any rotation in the gas cloud is conserved (and
   causes planets to revolve and rotate)
•A protostar star is form
• As the gas is compressed by gravity, the core of the
protostar increased in pressure and temperature
until nuclear fusion occurs: Hydrogen  Helium

The star becomes stable and stays this way  our
Solar System 2019 - UD Physics
History and Formation of the Solar System

   The planets of the Solar System formed from a nebula of
    gas, dust, and ices coalescing into a dusty disk around the
    evolving Sun.
   Within the disk, dust grains and ices coagulated into
    growing bodies called planetesimals.
   These then collided and were swept up together to form the
    planets and their satellites
   The fact that all planets revolve around the sun in the same
    direction and most rotate in the same direction shows the
    left over energy from the initial collapse of the nebula. 5
Solar System 2019 - UD Physics
Early solar system evolution
   Early in the sun’s life (as the planets were forming), the
    sun had a very strong solar wind (from flares)
       Charged particles streaming out of the suns atmosphere
       This solar wind was produced as the nuclear reactions in the
        core of the sun started.
       The sun produces a weaker solar wind today that fluctuates with
        the sunspot activity of the sun – more sunspots, more solar wind.
            Solar wind “storms” cause the Northern Lights (auroras)
   This early strong solar wind and collisions between
    particles helped to “pushed” much of the material that
    had not been formed into planets out to the farther
    reaches of the solar system
       This helped formed the Kuiper Belt and the Oort Cloud (the
        source of long period comets)

Solar System 2019 - UD Physics
The end of our solar system
• The planets form about the same time as the sun.
• At the end of our suns normal life, hydrogen is depleted
in the core of the sun. Gravity takes over and causes the
core to heat up further.
• BUT fusion continues in a shell outside the core. Our
sun will “bloat” up to a red giant. The earth will be fried
• Helium will start to be fused to carbon in the core of our

•The sun will be convulsed and throw off half its mass as
a planetary nebulea -- solar system destroyed
• A white dwarf (carbon) star will be left behind       7
Solar System 2019 - UD Physics
Objects of the Solar System: Planets
   A planet is … in orbit around the Sun,
   Has sufficient mass to assume a hydrostatic equilibrium (nearly round)
    shape, and
   Has “cleared the neighbor-hood” around its orbit.

Solar System 2019 - UD Physics
Dwarf Planets
   A dwarf planet is …          Pluto (spherical with 1 moon- Charon)
   In orbit around the Sun      Ceres
   Has sufficient mass for          Ceres is the largest asteroid in the main asteroid
    its self-gravity to                belt. It is a dwarf planet because of its round
    overcome rigid body                shape
    forces so that it                Rocky (high density)
    assumes a hydrostatic
                                     In asteroid belt
    equilibrium (nearly
    round) shape,                   Between Mars &
   Has not “cleared the            Jupiter
    neighbor-hood” around
    its orbit, and
   Is not a satellite of a
    planet, or other
    nonstellar body.

                                 Haumea
                                 Dwarf planet beyond Neptune, About the size of Pluto
                                  with 2 moons, fast rotation rate
                                 Collision likely caused it to rotate so fast and to form
                                  its 2 moons – Kuiper belt object Ceres
Solar System 2019 - UD Physics
o                                                                 Dwarf Planets
 Remarkably complex geology –
     Surface is 98% frozen nitrogen plus a little methane and
      carbon monoxide
     New (No craters) and old (cratered) surfaces next to each
     Nitrogen ice glaciers
     Ice water mountains
     Possible cryovolcanoes                                                   Water ice
                                                                               glacier on
                                Nitrogen ice
                                glacier on

Atmosphere on Pluto – very thin ~ 0.00001 atmosphere
Nitrogen, methane, particles (causes haze),

Dwarf Planets

   Makemake Dwarf plant beyond Pluto
      It and Haumea and Eris are responsible for demoting Pluto to a dwarf planet
      No close up pictures
      870 miles in diameter, no atmosphere
      Takes 310 years to go around the sun, in the Kuiper belt
      Frozen layer of methane and possibly ethane and nitrogen
      One moon
   Eris About the same size as Pluto
        No close up pictures
        1400 miles in diameter – a little smaller than our moon.
        Takes ~5 hours for sunlight to reach Eris.
        557 years to orbit the sun
        In the Kuiper belt
        One very small moon – allows astronomers to determine the mass of Eris

   Some 7000 asteroids
Asteroids                    have been identified so
                            Most are in a belt or
                             band between the
                             orbits of Jupiter and
                            Jupiter probably
                             stopped planetisimals
asteroid Gaspra              formed at the birth of
                             the solar system from
Why is Gaspra not a
dwarf planet and Ceres       coalescing into a
is ?                         planet.              15
   The Kuiper Belt is made up of
Kuiper Belt & Oort cloud       millions of icy and rocky objects
                               that orbit our Sun beyond the orbits
                               of Neptune and Pluto.
                              These are planetesimals that did
                               not combine to make planets.
                              It is the source of short period
                              Oort Cloud is spherical and is at
                               the outer edge of our solar system
                              It was pushed out there at the start
                               of the solar system by strong solar
                               winds and by the gravity of the
                               large gas giant planets
                              The Oort cloud acts as a reservoir
                               for the long-period comets

Charon             Biggest moon of Pluto.
                   Half the size of Pluto  double dwarf system
                   New Horizon’s fly by
                   Orbits Pluto every 6.4 days

Mimas -- moon of Saturn
                   Cassini space craft image.
                   246 miles in diameter – smallest spherical body
                   Mostly water ice (same density as water)
                   Giant impact crater
                   Not as big as Titan, the largest moon of Saturn
                   Tidally locked like the Earth’s moon.      17
Phoebe  another moon of Saturn
                         Cassini probe took this close up
                        Roughly 120 miles in diameter
                        Orbits Saturn every 18 months
                        Likely a “captured” object
                        May be a captured Centaur
                          asteroid – material from the
                          beginning of the solar system

                          Centaur asteroids

Centaur A cross between asteroids and comets
                         Across the orbit of Neptune
                         Considered very old and likely
                          composed of material from the
                          beginning of our solar system

Asteroid Belt
                The heaviest
                 concentration of
                 asteroids is in a
                 region lying
                 between the orbits
                 of Mars and
                 Jupiter called the
                 asteroid belt.

Facts about the Asteroid Belt
                                   Traveling through the
   The total weight of all         asteroid belt in a space
    the asteroids in the            ship would not be like
    asteroid belt is about          what you see in a
    1/35th of that of our           science fiction film.
                                   In addition to the belt
   Ceres, the largest              asteroids, there are
    asteroid (a dwarf               others classes of
    planet), is about 1/3 the       asteroids based upon
    total weight of all the         their location and orbit
    asteroids!                      in the solar system:
   Even though there are           Apollo (Earth crossing),
    a lot of asteroids, the         Amors, Atons, Trojan
    asteroid belt is mostly         (along the orbit of
    empty space.                    Jupitor) and Centaurs.

   The first and only
    interstellar object that
    travel through our solar
    system in 2017
   Its very high speed
    proved it came from
    outside our solar
   Its changing light output
    indicates that it is very
    long like a cigar.

225088 2007 OR10
   Binary object (a dwarf
    planet with a moon)
    beyond the orbit of
    Neptune (Trans
   780 miles in diameter
   Largest unnamed
    object in our solar
   Slightly larger than
   Discovered in 2007

     New Horizons
• Interplanetary space probe.
• Launched in 2006
• Primary mission: Flyby Pluto and later
   a Kuiper belt object (Ultimate Thule)
• Detected “hydrogen wall”
(a region of hot hydrogen at the edge of
the solar system where the solar wind
Hits the interstellar

Missions -- Dawn
• Ion propulsion used to go to the
  asteroid belt and observe Ceres (a
  dwarf planet) and Vesta
• First to orbit two different targets
• Current in a uncontrolled orbit around
• It ran out of fuel

Missions:Cassini -Huygens
• Probe sent to study Saturn
• Huygens probe attached to Cassini was
  dropped to the surface of Titan
• Many crossings of the ring system
• Purposely flown into Saturn to burn up to
  avoid any possibility of contaminating
  Saturn’s moons

Missions -Lucy
• To be launched in about 3 years
• Explore the Trojan asteroids
• Trojans believed to be remnants of
  the early solar system that became
  locked into Jupiter’s orbit and low
  energy points.

Missions:Voyager 2
Launched in 1977
Only probe to fly by Uranus and
Crossed the heliopause into interstellar
Remains an active mission to measure
the interstellar media.

Accepted theory of the Origin of
         our moon…
                • A small planet named
                  “Theia” slammed into earth
                • It may have side swiped the
                  earth, created the moon,
                  and Theia was thrown out
                  of the solar system
                • OR it blew apart the earth
                  making the combined
                  Earth+Theia into the Earth-
                  moon system.
Evidence that Theia is part of the
      Earth – moon system
• Ratio of oxygen isotopes provides a unique
  signature to each planet in our solar system
  – Oxygen normally has 8 protons and 8 neutrons
    That is called 16O
  – Some oxygen has 8 protons plus 9 neutrons or
    10 neutrons –Called 17O to 18O
  – Ratio of 16O to 17O to 18O is the same in the
    earth and the moon
  –  Indicates that they were made from the same
    material = Theia+ the original Earth
More Evidence for the impact
       origin of our moon
• Earth has a iron core – source of our
  magnetic field
• Moon does not – any iron in Theia merged
  with earth’s iron core.
  – The material thrown off during the collision
    would have been less dense.
• The moon is the largest moon relative to the
  planet it is orbiting
  – A substantial amount of material would have
    been thrown off from the collision – making a
    large moon.
Estimating apparent age of

                   • Crater density
                   • Which is older?

Tidal effects on Earth (and our moon)
Tidal Effects
 The gravity of our sun and our moon yanks the near side of
   the oceans to form a high tide.
 Gravity also tugs at the (solid) earth away from the oceans
   on the far side. Hence high tides on the far side!
 Our moon "solid ground" also has tides – very small

                                             Tides also occur in
                                             the crust – causing
                                             frictional heating like

Tidal effects on Earth (and our moon)
1.   A long time ago… The tidal forces of Earth on the Moon
     slowed down the rotation of the Moon (while speeding up the
     rotation of the Earth).
2.   The Moon eventually keeps the same face toward the Earth,
     becoming tidally locked (as it is now)
3.   The tidal forces of the Moon on the Earth slow down the
     rotation of the Earth, while speeding up the orbital motion of
     the Moon
4.   The Moon spirals away from the Earth, increasing its angular
     momentum, compensating for the lost angular momentum of
     the Earth rotation.
5.   The Earth eventually keeps the same face toward the Moon,
     becoming tidally locked.
6.   The system stops evolving and remains in this configuration
     forever (except as influenced by external forces).          34
Tidal effects on   Tidal Effects
                    The gravity of Jupiter and
   satellites         its large moons yank its
                      satellite Io every which
                    Io’s "solid ground" tides are
                      more than five times as
                      high as Earth’s highest
                      ocean tides!
                    This causes a lot of friction
                      and heating of the crust of
                    This causes sulfur
                      volcanoes across the face
                      of Io
Lava (Basalt) filled ancient craters to form the Mare

                                          Our Moon

                                              Lots of
                                       craters –most
                                       from impacts
But mare on the moon not like
     volcanoes on Earth
                    • Mare mostly
                      caused by the
                      process that
                      formed the moon
                    • There are
                      volcanoes on the
                      moon that likely
                      formed like that on
                      Earth (next slide)
                    • All now extinct
Cross section of our moon
Essentially dead – no plate techtonics
(like the earth). No strong magnetic field
(no large molten iron inner core)

We all know about solar eclipses (yes?)
                       • The moon
                         completely blocks
                         out the sun’s light in
                         a very small spot on

                       • August 21st

• Here is what it looks
  like if you were
  standing near the
  sun (HOT!!) and
  looking through a

Partial Solar Eclipses
   If the penumbra passes over you, only part of the Sun's
    surface will be blocked out.
   You will see a partial solar eclipse, and the sky may dim
    slightly depending upon how much of the Sun's disc is

            Partial Solar Eclipse

   In some cases, the moon is far enough away in its orbit that the
    umbra never reaches the Earth at all. In this case, there is no
    region of totality, and what you see is an annular solar eclipse.
   In an annular eclipse, only a small, ring-like sliver of light of the
    Sun’s disk is visible. ("annular" means "of a ring").

                                             Annular Solar


But… did you know that you can “see”
 (barely) the “dark” side of the moon
      during a total solar eclipse
                      • But how can that
                      • The earth reflects a
                        lot of light back to
                        the moon – like ~10x
                        that of a full moon.
                      • So there is enough
                        sunlight reflected off
                        the earth to
                        illuminate the “dark”
                        side of the moon!!!46
We all know about Lunar eclipses

                   • The Earth completely
                     blocks out the sun’s
                     light falling on the
                   • BUT – the whole
                     moon can be
                     darkened – why?
                   • Jan 31, 2018
                   • Jan 20/21, 2019
What does a lunar eclipse look like
 from the surface of the moon?
                     • Like this!!!!
                     • The size of the earth,
                       appears to be much
                       larger than the sun
                       as viewed from the
                     • So… it completely
                       blocks the sun out
                       when there is a lunar

From the surface of the moon, the
Earth appears to go through phases…
        just like the moon…

                 • So… What phase is the
                   moon when the Earth is

We always see the same face of the moon…
But actually can see more than half of the moon…
  Libration – or apparent wobble of the moon.
The moon appears to “wobble” up and down and left
to right a little

We always see the same face of the moon…
What do you think the earth looks like from the

                  Click here

After a really long time, a rectangle is formed…

This is due to the Moon’s rotation rate is
slightly out of sync with its orbital rate around
the earth
                                       This is due to the Moon’
                                       tilt of its axis

                    This is also the wobble from


• Gigantic volcanoes – Olympus Mons is the
  largest found in the solar system
  – Would cover the state of Arizona
  – Similar composition to volcanoes on Earth
  – None active

  – No current magnetic field on Mars means no molten
    core to drive active volcanoes.
  – But Mars had a molten core in the past that
    produced these volcanoes
Global Mars mosaic from Mars surveyor

North polar cap at top, Volcanoes to left, Enormous rift
valley left of center, clouds, craters at bottom
Olympus Mons

  Huge shield volcano

  The largest in the solar system
  But no clear evidence of plate techtonics
Mars North Polar Cap from Mars surveyor
Extremely cold temperature,
The white stuff is frozen carbon dioxide not water
but ….

                        Ice water is
                       under this 
Reflected Radar mapping of what is under the

       Ice layers
    Base rock

                    Shallow Radar instrument on NASA's
                    Mars Reconnaissance Orbiter for mapping
                    underground ice-rich layers of the north
                    polar layered terrain on Mars
                    The penetrating radar reveals icy layered
                    deposits overlying a base rock.

Mars South Polar cap
                  • Photos from Mars Global
                  • The bottom photo was taken
                    during summer. This is
                    essentially “permafrost” that is,
                    it does not go away.
                  • CO2 frost grows much larger
                    during winter.

                  • Picture taken by Mars Global
                    Surveyor   59
Evidence for glaciers on Mars
                       •   Glaciers are largely restricted to
                          latitudes above 30° latitude. Based on
                          models of the Martian atmosphere, ice
                          should not be stable at the surface near
                          the equator. Glaciers near the equator
                          must be covered with a layer of rubble
                          or dust preventing the sublimation of the
                          ice into the atmosphere.
                       A terminal moraine is in the rectangle.
More evidence for glaciers on Mars


Valles Marineris
A gigantic rift valley   62
Mars interior – was molten iron – had a magnetic
field that has since disappeared when solidified

Mars moons
• Geologically inactive. Captured asteroids.
• Not large enough to have enough gravity to
  make them spherical.

• Dense atmosphere / completely clouded over
  – Run away greenhouse heating – very hot surface

  – Can’t easily “see” the surface but….
    Radar used to “see” the surface.
• Radar has seen evidence of lava flows and
  volcanism                               65
• Radar images of Maat
   Venus                    Mons
                          • Unclear if it is an active
                          • Probably formed like
                            those on Earth & Mars
                          • No craters

• But no clear evidence
  of plate techtonics
No magnetic field –very slow rotation rate and lack of
internal movement of conductive material that can create a
magnetic field
• No air
• First satellite pictures showed a surface a lot like the
• Very hot on the sun side (melts lead)
• Very cold on the shady side
• “Inferior” planet
• Show phases like the moon
• But very difficult to see – always close to the sun
• BUT recent satellite images suggest…. Extinct
Tectonic activity on Mercury
• Over thrust
  faults caused by
  contraction of
  mercury when

Cross section of Mercury
Molten core should create a strong magnetic field
There is a magnetic field but 200x weaker than

Largest planet
Rotates every 6 hours, appears “flattened”
Gas giant, would “float” on water
Visible in a pair of binoculars
Four major moons
  The closest to Jupiter is Io
  Many sulfur volcanoes
  Caused by the friction heating from the strong
  tides produced from Jupiter’s gravity.
Totally different than Earth, Moon, Mars, Venus or
  Mercury                                        71
Io and sulfur volcanoes Tidal Effects
                              Io shows the same face to
                               Jupiter – gravitationally
                               locked (like our moon)

Structure of Io
• Determined using Galileo spacecraft.
• Low density crust 20-30 miles (grey)
• Molten magma “ocean” -- red brown & orange(source of
                                   • Io’s magma ocean is
                                     very conductive and
                                     deflects the Jupiters
                                     strong magnetic field
                                     lines (blue)
                                   • Iron and iron sulfide core

• the largest asteroid and the only dwarf planet in the inner Solar System,
  orbiting in the asteroid belt between the orbits of Mars and Jupiter. It is a
  rock–ice body 950 km (590 mi) in diameter and the smallest identified dwarf
  planet. It surface is probably a mixture of water ice and various hydrated
  minerals such as carbonates and clay minerals. It appears to be
  differentiated into a rocky core and icy mantle, and may harbor an ocean of
  liquid water under its surface,

    Hubble space telescope
            image                                                        74
Planetary Motions: Rotation

   A planet or dwarf planet or asteroid will rotate
    on an axis. Its rate of rotation gives the
    length of a “day” on the object.

Kepler’s First Law of Planetary Motion
   The path of the planets about the sun are
    elliptical in shape, with the center of the sun
    being located at one focus. (The Law of Ellipses)

Kepler’s Second Law of Planetary
   The line joining a planet to the Sun sweeps out equal
    areas in equal times as the planet travels around the

Kepler’s Third Law of Planetary
   The square of the total time period (T) of the
    orbit is proportional to the cube of the average
    distance of the planet to the Sun (R). (The Law
    of Harmonies)

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