Download The Solar System 2/21/13

The Solar
System
2/21/13
Logistics
• Reminder: MRS 1 due tuesday!!
• Collect Light & Atoms, Blackbody Radiation
and Doppler Shift!!
2
Taking Stock of the Solar System
• Sun - a very basic G5 star
about 4.5 Gyr old
• Have 8 planets
– terrestrial planets : mercury,
venus, earth, mars
– gas giant planets : Jupiter,
Saturn
– ice giants : Uranus and
Neptune
• Asteroid Belt - between
mars and Jupiter
• Kuiper Belt - beyond
Neptune
The Sun
4
Our Star, the Sun
The Sun is the Largest Object in
the Solar System
• The Sun contains more than 99.85% of the
total mass of the solar system
• If you put all the planets in the solar system,
they would not fill up the volume of the Sun
• 110 Earths or 10 Jupiters fit across the
diameter of the Sun
Eight
Comparisons among the nine planets show
distinct similarities and significant
differences
The Four Terrestrial Planets
Mercury
Distance to Sun = 0.47AU (0.39, e=0.2)
Mass = 5.5% Earth Mass
Radius = 38.3% Earth Radius
Density slightly less than Earth’s
Essentially no atmosphere
“The Cratered Planet”
The Four Terrestrial Planets
Venus
Distance from Sun = 0.72AU
Mass = 82% Earth
Radius = 95% Earth
Much hotter, 90 x pressure of Earth
“Runaway Greenhouse Planet”
The Four Terrestrial Planets
Earth
Earth
• Distance from Sun = 1 AU
• Mass of Earth = 5.9 x 1027g
• Density 5.5 g/cc (water 1 g/cc)
The Four Terrestrial Planets
Earth
• The largest terrestrial planet
• Highest density
• Only planet
with:
–
–
–
–
Plate tectonics
Liquid water on surface
Substantial Oxygen in atmosphere
Life
Earth
• Clouds/Atmosphere
– Erosion of surface
• Albedo = 0.37
• 71% of surface covered in water
• Geologically active:
– Plate tectonics
– Volcanoes
The Four Terrestrial Planets
Mars
Distance from Sun = 1.5 AU
Mass = 10% of Earth’s Mass
Radius = 50% of Earth’s Radius
Density less than Earth’s (4gm/cc)
The Gas and Ice Giants
JupiterT
ext
Distance From Sun= 5.2 AU
Mass = 318 x Earth’s Mass
Radius = 10-11 x of Earth’s Radius
Density = 1.3 g/cc (Earth is 5 g/cc, Water is 1 g/cc)
The largest planet, known for its great red spot
The Gas and Ice Giants
Saturn
Distance From Sun= 9.6 AU
Mass = 95 x Earth’s Mass
Radius = 9 x of Earth’s Radius
Density = 0.7 g/cc (Earth is 5 g/cc, Water is 1 g/cc)
The second largest planet, known for its rings
The Gas and Ice Giants
Uranus
Distance From Sun= 19.2 AU
Mass = 15 x Earth’s Mass
Radius = 4 x of Earth’s Radius
Density = 1.2 g/cc (Earth is 5 g/cc, Water is 1 g/cc)
The Gas and Ice Giants
Neptune
Distance From Sun= 30 AU
Mass = 17 x Earth’s Mass
Radius = 3.9 x of Earth’s Radius
Density = 1.6 g/cc (Earth is 5 g/cc, Water is 1 g/cc)
Main Asteroid Belt
• Between Orbits of Mars and
Jupiter from 2-3.5 AU
• 105 objects catalogued,
more observed, 49million
awaiting classification
• Asteroid spacing still
millions of miles, but can
collide, velocities thousands
km/hr
• Asteroid “Families”
– Asteroids with similar orbits
– Originate from the breakup of
bigger asteroids
http://apod.nasa.gov/apod/ap130218.html
18
Categorization
• Planet - (1) orbit around the Sun,
(2) enough mass for gravity to
make spherical, (3) cleared its
orbital neighborhood of debris
• Dwarf Planet - satisfies (1) and
(2) : Pluto, Ceres, Eris
• Small Solar System Bodies - not
planets, dwarf planets or moons
Dwarf Planets
• Pluto – 40 AU, e=0.25
– Largest moon Charon more
than half its size
– Pluto - 2380km, Charon
1190km
• Ceres – 2.76 AU
– In Main asteroid belt, first
discovered Asteroid 1855
(mistaken for planet)
– D~ 940km
• Eris – 97 AU from Sun, e=0.44
– Kuiper Belt
– D~2400km
Inner planets vastly different than outer
planets
• Inner planets are rocky, like Earth (high density)
• Outer planets are gas or ice (low density)
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Conditions That Theories Should Address
• What we know:
– planets have orbits nearly in a
plane (ecliptic)
– planets orbit the sun in the same
direction (prograde)
– terrestrial planets
• small bodies made of heavy
elements (C, O, N, Fe, Si)
• close to the Sun
– jovian planets:
• large bodies made of light elements
(H, He)
• far from the Sun
– sun, primarily H, He
22
The solar system formed from a cloud of cold gas
and dust called the solar nebula about 4.6 billion
years ago
Molecular Clouds: Stellar Nurseries
• Huge clouds of gas and
dust in the galaxy
– molecular hydrogen (H2)
– many light-years across
– contain 10s to 1000s of
solar masses of material
24
Molecular Cloud Collapse
• Molecular clouds can
collapse in onto
themselves
• Dense clumps of
collapsing molecular
clouds are regions
where stars form
25
Star and Disk Formation
• Dense clumps in a
collapsing molecular
cloud form a disk
• Disk is called a “protoplanetary disk” or a
proplyd
• Protostar is at center of
the protoplanetary disk
26
Star Formation
• Protostar accretes material from
disk
– center is under extreme pressure
– center gets hotter and hotter
– nuclear fusion begins
• Now a full-fledged star
27
The Formation of the
Protoplanetary disk
• As the original gas cloud
collapses, it begins to
rotate faster
– conservation of angular
momentum
• As the cloud shrinks, it
also flattens
28
The Protoplanetary Disk
• Hydrogen and Helium are most abundant
• O, C, N, Si, Fe also fairly common
29
Condensation in the Protoplanetary Nebula
• Chemical composition of
solar system arranged by
distance from the protosun
• Heavy Elements
– high condensation temperatures
– close to sun
• Light Elements
– low condensation temperatures
– far from sun
• Same for molecules
30
Collisions dominated the early solar system
• dust collects together into planetesimals
• planetesimals collect together into protoplanets
• Protoplanets gather up left over debris and
became planets
Tutorial: Temperature and Formation of
Our Solar System – p. 111
• Work with a partner!
• Read the instructions and questions carefully.
• Discuss the concepts and your answers with one another.
Take time to understand it now!!!!
• Come to a consensus answer you both agree on and
write complete thoughts into your LT.
• If you get stuck or are not sure of your answer, ask
another group.
G. Marcy and P. Butler