Transcript Our Nearest Star “The Sun”

Solar System
• Read Your Textbook: Introduction to Physical Science
– Chapter 20
– Chapter 21-26
• Answer Questions
– Chapter 20: Q4;P1,4,6,9 W3
– Chapter 21: Q2,5-8 P2,3 W3
– Chapter 22: Q1-3,12;P2,3,7 W1,4
– Chapter 23: Q2,4,6,9 W1
Solar System Scale
The Sun has 99.85 % of the mass of the solar system
Jupiter has 2/3 of the remaining that formed planets
Planetary Orbital Inclination
Our Solar System is Very Nearly Disk Shaped
Angles of the planets orbits are shown with respect to the
ecliptic (earth-sun orbit).
Planetary Densities
moon
Two Planet Types
• Terrestrial (Earth-Like) Planets
– High Densities (mostly metals and solids)
– Small sizes
– Near the Sun
• Jovian (Jupiter-Like) Planets
– Low Average Densities (mostly gases and ices)
– Large sizes
– Far from the Sun
Ages Determined
• Terrestrial Rock Samples (Greenland, Canada, Australia)
– 3.9 billion years
• Lunar Rock Samples (Apollo Missions)
– 4.1 billion years
• Meteorite Samples
– 4.5 billion years
• Solar modeling
• The solar system is roughly 4.5-5.0 billion years old.
Solar Nebula Theory
A complete description of the formation of the solar system
must explain the observed characteristics:
Disk-like Nature
A complete description of the formation of the solar system
must explain the observed characteristics:
• The disk shape nature of the solar system
– All planets orbit within 10 degrees of the Earth-Sun orbit
– Common Rotations and Revolutions
Density Variations
A complete description of the formation of the solar system
must explain the observed characteristics:
• The disk shape nature of the solar system
– All planets orbit within 10 degrees of the Earth-Sun orbit
– Common Rotations and Revolutions
• Terrestrial (Earth-Like) Planets
– high density, rocky, small, close to the sun
• Jovian (Jupiter-Like) Planets
– low density, gaseous, large, farther away from the sun
Common Age
A complete description of the formation of the solar system
must explain the observed characteristics:
• The disk shape nature of the solar system
– All planets orbit within 10 degrees of the Earth-Sun orbit
– Common Rotations and Revolutions
• Terrestrial (Earth-Like) Planets
– high density, rocky, small, close to the sun
• Jovian (Jupiter-Like) Planets
– low density, gaseous, large, farther away from the sun
• Common Ages
• Space Debris
– asteroids, comets, ring systems
Orion
Star formation
region
in the
constellation
of Orion
visible to
the unaided
eye.
Star Formation Regions
Belt and Sword of Orion
Orion Nebula & Horse Head Nebula
Nebulosity
Hot new stars illuminate the gas and dust of the horse head
nebulae in Orion
Infant Stars
Orion Nebula Trapezium
Stellar Nurseries
• New, Young stars are associated with gas and dust.
Eagle Nebula
A Star is Born
Proto-Stars
The Orion Trapezium Region in Infra-Red Light
Angular Momentum Conservation
The ice skater, the ballerina, the earth’s rotation and a child’s
top, believe it or not, all have a lot to do with each other, and
the formation of the solar system.
• Angular Momentum:
– Rotating Objects Have It
– They Want To Conserve It
• Depends on Mass
• Depends on velocity
• Depends on Distribution of Matter About the Rotation Axis
Sphere To Disk
When a spherical proto-stellar cloud begins collapsing,
it has some inherent rotation (and thus angular momentum)
associated with it. As material moves to smaller radii,
the rotation increases, like the ice skater and ballerina
in a spin bringing their arms in toward the
rotational axis.
Material along the axis does not spin as much as material
near the “equator” and so does not have as much angular
momentum to save. Therefore, the material at the poles
falls closer to the center.
Rotation
Gravitationally collapsing rotating spheres tend to create
flattened spinning disks.
The inner parts of the disk rotate faster than the outer parts.
Solar Nebula
Solar
System
Formation
Proto-Stellar Disk
Radiation from the new star,
tries to escape.
The infalling disk material
absorbs it and cuts it off.
Its only escape is along the
poles of rotation where
the disk is thinner.
Eta Carina
b Pictoris
Disk
material
around
other
stars.
Proto-Stellar Accretion Disk
• Bi-Polar Outflow
Planetary Orbits
KEPLER'S III LAW:
THE RELATION BETWEEN ORBITAL PERIOD P (years) AND
AVERAGE DISTANCE a (A.U.) IS A CONSTANT FOR THE
SOLAR SYSTEM
P2/a3 = constant
Planetesimal Coalescence
Eddies,
whirlpools,
and other
density variations
cause
planetesimals
which later
accrete and
collide to
form into
the planets.
Proto-planet Accretion & Coalescence
• N-body Coalescence
Planetary Densities
Condensation Temperature
Temperature (K)
Temperature decreases with distance from the sun.
2000
1500
Metal Oxides
Metallic Iron and Nickel
Silicates
1000
750
500
Sulfides
Water Ice
Ammonia and Methane Ices
0.1 0.5 1.0
5.0
Mercury
Jupiter
Earth
10.0
Saturn
Distance (Astronomical Units A.U.)
40.0
Pluto
Solids and Density
Temperature (K)
Density decreases with distance from the sun also in the
same way that the temperature does. Only matter with
higher density, existed as solids (not gas) at the higher
temperatures found near the proto-sun.
2000 Metal Oxides
1500
1000
750
500
Metallic Iron and Nickel
Silicates
Sulfides
Water Ice
Ammonia and Methane Ices
0.1 0.5 1.0 5.0
Mercury Jupiter
Earth
10.0
Saturn
Distance (Astronomical Units A.U.)
40.0
Pluto
Solar Nebula Composition
• The denser materials are able to exist as solids at
higher temperatures. The only solids found in the
inner portions of the solar nebula are the dense
metals that form the rocky terrestrial planets.
• This dense material also exists at large radii from
the proto-sun.
• Less dense ices only exist in the outer solar nebula.
Pressure Balancing Gravity
When the star
begins generating
energy within,
radiation and gas
pressure build up
to counteract
gravity.
Radiation and winds
move outward,
away from the star.
Density Evolution
Density (g/cm3)
The initial distribution of material in the solar nebula (A) changes, as
the sun accretes material and finally “turns ON” (B), and material is
blown out of the interior (C).
A
B
C
0.1 0.5 1.0
5.0
Mercury
Jupiter
Earth
10.0
Saturn
Distance (Astronomical Units A.U.)
40.0
Pluto
Terrestrials versus Jovian Planets
• Terrestrial planets formed from the materials that could
exist at the highest temperatures. They are higher density
rocky bodies close to the proto-sun.
• Jovian planets formed from both high density and the
much more abundant low density material that was able to
exist as solids far from the proto-sun. There was much
more material to draw from (both metals and ices) as
compared to material the terrestrial planets had available.
Therefore, the jovian planets are less dense and farther
from the sun.
• Why are the Jovian planets so much larger?
Clearing the Inner Disk
• Once the Sun had “turned-ON”, the material in the inner
disk was blown clear, thus truncating the accretion and
coalescence processes of the terrestrial planets. Their
growth was “stunted” by the birth of our Sun.
• The jovian planets were able to draw on the metals and
much more abundant ices and grew very large.
• Jupiter is the largest planet probably because:
– It is the nearest “far” planet (existed in a higher density region)
– More numerous ices could also be accreted as well as metals
– Not stunted by clearing of the inner disk (may have benefited)
Are We Unique?
• Solar Nebula Theory Explains
–
–
–
–
–
–
The disk shape nature of the solar system, including orbits
Existence of Terrestrial Planets
Existence of Jovian Planets
Common Ages (Everything Formed At Once)
Space Debris (Left Over Junk)
Planets form as a by-product of star formation
• Solar Nebula Theory Predicts
– Accretion disks should be found around young stellar systems
– Planets form as a by-product of star formation
– Terrestrials close, Jovians far, and a large “Jupiter” in the middle
• The sky should be full of solar systems of similar nature!