Download Solar System Review inner and outer 2015

Solar System Review
Nebular Theory
Eagle Nebula
• Solar System
formed through
the collapse of a
large cloud of gas
under its own
gravity
Lagoon Nebula
Gravitational Collapse
• Start out with a large cloud of gas
–A few light years in size with a very
low density
–Very cold temperatures
• Something triggers the collapse
–Supernova explosion
• Cloud can no longer support itself
against its own gravity. Continues to
collapse
More Gravitational Collapse
From Cloud to Solar System
• Energy Conservation
–Heats the cloud
• Ang. Momentum
–Causes the cloud
to spin faster
• Cloud Flattens
–Mergers between
particles average
out the velocities
How do planets form?
• Through accretion
–Small particles are able to build
larger complexes of particles
–Eventually the complex becomes
large enough to “attract” pieces
through gravitation –
planetesimals
–Only the largest planetesimals
survive to become planets
Planet Formation
• Terrestrial planets (Mercury, Venus,
Earth, and Mars) all formed beyond a
distance of 0.3 AU
–Rock could not condense within this
distance
• Jovian planets (Jupiter, Saturn,
Uranus, and Neptune) all formed
beyond the frost line (3.5 AU)
–Hydrogen compounds formed the
cores of these planets
Jovian Planets • Gravity of icy
planetesimals was
large enough to
capture hydrogen
and helium gas
• Continued to grow
larger as mass
increased
• Large masses also
explain the large
number of moons
How old is the Solar System?
• Oldest Earth rocks found to be 4 billion years old
• But this only tells us the time since rock last
solidified, after the Heavy Bombardment
• Solar System must be older than 4 billion years
• Moon rocks give an age of 4.4 billion years, but
they also re-solidified at some point
• Need objects that have not vaporized since the
solar nebular collapsed
– Meteorites!
– Found to have an age of 4.55 billion years
Astronomy
• To the study of motion
The Planets of Our Solar System
The Inner Planets
Sizes to Scale
Mercury
Venus
Earth and Moon
Mars
Interior Components
• The interiors of all the terrestrial bodies
consist of the same components
–Core – Highest density (iron, nickel)
–Mantle – Rocky material, around core
–Crust – Lowest density (granite,basalt)
• Material separated when Earth was still
molten
–Densest material “sank” to the center
Interior Structure
Comparing Interiors
Active geology
Inactive geology
Changing Appearances
• Before the Heavy Bombardment, the
inner planets probably looked very
similar, aside from size
• Today we can see they look very
different, but why?
–Impacts – Asteroids/Comets striking
–Volcanoes – lava flows
–Tectonics – Formation of mountains
–Erosion – Wears down structures
• Always
circular in
structure
• Produce a
large
amount of
debris that
litters the
surrounding
area
• Seen on all
terrestrial
planets
Craters
Left: A bowl
shaped crater
Top: Crater
with a central
peak; similar
to dropping
an object in
water
Mercury
• Heavily cratered
appearance
• 88 day orbit with a 59 day
rotation rate (slow)
• Temp ranges between
425°C and –150°C
• No atmosphere
– Too close to the Sun
– Too small in size
Activity on Mercury
• Very little if any – Dead planet
• Lava plains, although no
where near as large as
those found on the moon
• Relatively few craters in
Caloris Basin suggests
volcanism after the Heavy
Bombardment
• Little or no erosion
Caloris Basin
Venus
• “Sister
Planet” to
Earth, but in fact is
quite different
• Thick cloud cover
prevents an optical
view of the planet
• Use radar mapping by
sending radio signals
to “see” surface
features
–Mostly rolling plains
–A few mountains
Venus
Surface image from the Venera 13 spacecraft
Volcanism on Venus
• Very few craters
seen on Venus
• Due to a
combination of
plate tectonics
and volcanism
• Few mountain
ranges and deep
trenches
• Large number of
shield volcanoes
Sif Mons – Shield Volcano
Erosion on Venus
• Nearly non-existent
–No evidence of
features eroding
• Extremely hot
temperatures exceeding
430°C
–Water/Ice cannot exist
• Very slow rotation rate of
243 days
–No wind of any sort
Ushas Mons
Radar image of the surface of Venus, assembled from Magellan data. Ganiki
Chasma and Sapas Mons are shown in the white box -- possibly the sight of
active volcanism. NASA/JPL
Our Moon
• Only terrestrial
planet with a large
moon.
• Collision with a Mars
sized object
–Moon has a similar
composition to that
of Earth’s surface
–Smaller proportion
of vaporized
materials (water)
Our Moon
• Very similar in appearance to Mercury
• Much larger lava basins
• During differentiation, magma rose to the surface, creating
magma oceans
• Must have a low viscosity due to their large size
History of Mars
An actual image
of Mars. As you
can see, Lowell
had quite the
imagination
Percival
Lowell’s
drawings
showing regions
of lush
vegetation and
canals to
transport water
Mars
Image of Mars from NASA’s Mars Exploration Rover Spirit
History of Mars
• One of the better
studied planets.
Multiple spacecraft
have landed on
Mars and taken
images and data
samples
– Vikings Missions (1976)
– Mars Pathfinder (1997)
– Spirit and Opportunity
(2004)
-Curiosity
(2012)
https://www.youtube.com/watch?v=KyktvC7w7Js
https://www.youtube.com/watch?feature=player_detailpage&v=924O-cnkvr0
• The only other planet
Erosion on Mars that shows significant
erosion
–Wind/Dust Storms –
Rotation rate similar
to Earth’s (1 day)
–Water – Numerous
images showing
features believed to
be created by
running water
An artist’s impression of the ancient ocean on
Mars, which lasted for billions of years more
than was previously thought. Credits: Mars
Geronimo Villanueva/Nasa
Impact Craters on Mars
• Shows numerous craters
–The northern
hemisphere contains
few craters and filled
in with lava plains
–The southern
hemisphere is at a
higher elevation and
contains many more craters
Mars and Volcanoes
• Mars has the largest volcano
in the solar system
• Volcanoes on Mars should
be dead based on size
– Recent analysis finds
volcanic rock at an age of
only 180 million years!
– May become active again,
but should die out within
the next 1-2 billion years
as the interior continues to
cool
Life on Mars?
• No Martians!
• Continuing to
search for past
life on Mars
• Best bet is to
look for
microbes
• Look ahead to
future missions
Asteroids
Ida
Ceres
Asteroids
• Rocky leftover planetesimals
–Pieces that were not picked up by the
inner planets
• Where are they?
–Most are in the Asteroid Belt between
Mars and Jupiter
–Trojan Asteroids – in Jupiter’s orbit
–Near Earth Objects (NEO’s) – those
that are close to Earth
The Outer Solar System
Neptune
Uranus
Saturn
Jupiter
Orbital radii:
Jupiter 5.2 A.U.
Saturn
9.5 A.U.
Uranus 19 A.U.
Neptune 30 A.U.
The Planets of Our Solar System
The Outer Planets
Jupiter
Saturn
Earth Included for Scale.
Uranus
Pluto
Neptune
Jupiter
• 11 times Earth’s
diameter (1/10 sun’s)
• 300 times Earth’s mass
(1/1000 sun’s mass)
• Visible surface is gas
(mostly hydrogen);
interior must be mostly
liquid, with solid core
• Fascinating banded
patterns, hurricanes,
great red spot
24 Jupiter rotations from Oct. 31st
to November 9th, 2000.
Moons of Jupiter (Galilean)
• Io: volcanically active,
covered with sulfur
• Europa: Covered with
ice, with liquid ocean
underneath
• Ganymede: Bigger
than Mercury, icy and
cratered
• Callisto: Also big, icy,
cratered
• Many smaller moons
(chunks of rock)
Io: Heated by tidal friction
Europa: Water beneath ice
Water is probably kept warm by tidal friction.
Could this be a place to look for life?
Moons of Jupiter
Saturn
• Prettiest planet in small
telescopes
• 9 times Earth’s
diameter
• 100 times Earth’s mass
(1/3 Jupiter)
• Gaseous surface, liquid
interior, solid core (like
Jupiter)
• Rings!
• Many moons
Saturn’s rings
Rings are mostly ice particles, from tiny
grains to boulder-sized chunks. Gaps are
created by tug of nearby moons.
Cassini Mission
Titan (Saturn’s largest moon)
Opaque atmosphere of nitrogen,
methane, smog. Surface (cold!) could
have liquid methane, other hydrocarbons.
Saturn’s other moons…
Uranus
• At the threshold of
naked-eye visibility
• Less than half the size of
Saturn, and nearly twice
as far
• Another gas giant planet
with rings (faint), many
moons
• Spin axis is tipped
sideways
Uranus
• Discovered by William
Herschel, 1781
• At the threshold of naked-eye
visibility
• Less than half the size of
Saturn, and nearly twice as
far
• Another gas giant planet with
rings (faint), many moons
• Spin axis is tipped sideways
Moons of Uranus
All are icy, smaller than our own moon.
Neptune
• Discovered by mathematics
(anomaly in orbit of Uranus)
in 1845-46.
• Can be seen in binoculars
(looks like a faint star)
• About the same size as
Uranus, but 60% farther
away
• Voyager 2 discovered a cool
blue spot, which has since
disappeared
• Largest moon, Triton
Pluto
• At 2300 km, Pluto is a dwarf planet
• Has most elliptical orbit: ranges from 4.4
to 7.4 billion km from Sun (2.8-4.5 billion
miles)
• Actually crosses orbit of Neptune
• Orbits in 248 years, 1.5 times Neptune
Properties of Pluto
• Discovered in
1930 by
Clyde
Tombaugh
Hubble ST image of Pluto & Charon
Pluto and Charon
• Pluto’s large moon Charon is almost
half as big as Pluto (1100 km)
• Orbits only 20,000 km away
• Pluto and Charon always keep same
face to each other (rotation locked)
• Pluto rotates, and Charon revolves, in
6.4 days
• Pluto has 4 additional moons
More on Pluto’s • Charon has about
1/8 the mass of
Moon Charon
Pluto
– Compared to our
moon which has
1/80th the mass
of Earth
• Charon also orbits
at a small distance
of only 20,000 km
– Our moon orbits
at 400,000 km
• A very thin
atmosphere of
nitrogen gasses
• Atmosphere thins as
Pluto approaches
aphelion
– Gas refreezes
onto the surface
• Atmosphere will rethicken when Pluto
makes its way back
to the Sun
Pluto’s Atmosphere
Pluto Mission
• Close-up images
would improve
upon our current
knowledge of
Pluto’s surface
features
• Mission to Pluto
(New Horizons) to
reach Pluto/Charon
in 2015
Pictures reveal diverse new features:
• Possible dunes
• Nitrogen ice flows that apparently oozed
out of mountainous regions onto plains
• A networks of valleys that may have
been carved by material flowing over
Pluto’s surface.
• Large regions that display chaotically
jumbled mountains reminiscent of
disrupted terrains on Jupiter’s icy moon
Europa.
The planets, to scale
Kuiper Belt Objects
• http://www.msn.com/en-us/video/wonder/billions-of-milesaway-from-earth-new-horizons-spots-a-wandering-object/viAAg34Dl?ocid=se
• Scientists Discover Pluto's 'Little Sister' Makemake Has Its
Own Moon
• Icy leftovers
• Two locations
–Kuiper Belt
–Oort Cloud
Comets
• Its existence was predicted with
mathematical modeling and computer
simulations, and was said to exactly
explain the strange clumping behavior of a
group of dwarf planets in the Kuiper Belt, a
field of icy objects and debris beyond
Neptune.
• http://www.msn.com/en-us/video/wonder/planet-9-just-gotweirder/vi-BBsGbES
Other Solar Systems?
• Detected 3,264 planets
(5-10-2016)
• Difficult to detect directly
–Even for the largest planets, light
from the star overwhelms any light
from the planet
• Use indirect evidence to search for
planets
–Gravitational tugs
–Transits
• Trio of Earth-like planets found near ultracool star may have the right conditions for
life
• http://www.msn.co
m/enus/news/world/trioof-earth-likeplanets-foundnear-ultra-coolstar-may-have-theright-conditions-forlife/arBBswIIE?li=BBnbfc
A Closer Look at
Our Solar System
http://www.astro.umn.edu/courses/1001/prevsem/summer104/lecnotes/256,1,Astronomy 1001
http://departments.weber.edu/physics/schroeder/astro/lectureslides/352,9,The
Outer Solar System
http://www.uwgb.edu/dutchs/CosmosPowerPoint/277,18,Pluto
http://www.astro.umn.edu/courses/1001/prevsem/summer204/lecnotes/256,1,Pluto and Earth