Transcript Giant Planets Neptune Uranus Saturn Jupiter Lecture 15: The Planets Homework Read Chapter 11: “Jovian Planet Systems” Homework: Mastering Astronomy due Friday at 6pm.

Giant Planets
Neptune
Uranus
Saturn
Jupiter
Lecture 15:
The Planets
Homework
Read Chapter 11:
“Jovian Planet Systems”
Homework: Mastering Astronomy
due Friday at 6pm.
Observing Project #2
Motions of Stars
At an exact time you specify, i.e. 7:00pm, go to a location
where stars are visible. Sketch the foreground objects
(buildings, trees, whatever) and the location of ~5 stars
(placed as best you can).
About a week later, at the same time and location, sketch
the new positions of the stars relative to the foreground
objects. Repeat each week for a total of four sketches.
Observing Project #2
Motions of Stars
In one paragraph, describe what motion of stars you observed (general
terms), and explain why this happened in terms of Earth’s motion.
Turn in:
– 4 sketches of the stars. Label at least two stars you used.
– One paragraph, as noted above.
Please include your name and your GSI's name. We will collect this
assignment at the beginning of class on 3 December. You may turn it
in to your GSI if you finish early.
Terrestrial (Rocky)
Outer 4 Planets: Gas Giants
The Solar System
Spacecraft Reconnaissance
1980’s: Voyager 1 & 2
Camera and
Spectrometer
Measures spectral lines:
Chemical composition
Visited all 4
giant planets
Voyager Spacecraft:
Movie of Jupiter
Approach of Voyager Spacecraft
In Rotating Frame of Reference
This is the Voyager 'Blue Movie'
(so named because it was built
from blue filter images).
It records Voyager 1's approach
during a period of 60 Jupiter days.
Notice the difference in speed and
direction of the various zones of
the atmosphere.
Voyager Spacecraft: Movie of Jupiter:
In Rotating Frame of Reference
Galileo Spacecraft
Visited Jupiter 1995-2003
•Launched from Space
Shuttle 1989
Galileo Spacecraft
Arrived: 1995
2003:
Dropped into Jupiter’s
Atmosphere:
Measure Chemical
Composition:
The 4 “Giant Planets”
“Jovian Planets”
• No solid surfaces !!!
Jupiter
H & He
(most common
atoms in universe)
Much higher mass & radius than Earth, Venus, Mars.
Saturn
H & He
Uranus
H2O,
H & He
Neptune
H2O,
H & He
(Textbook: “hydrogen compounds”
= water, methane, ammonia)
“Ice Giants”
All four Gas Giants have rocky cores
(silicates+iron) of 10-20 Earth masses.
Comparison of Sun’s and Jupiter’s
composition (as measured by the
Galileo Probe)
No solid surface and consists mostly of H & He.
Distinct interior layers, defined by increasing density inward.
Fractional composition in mass %.
Jupiter
H
Sun
Jupiter
Sun
0.742
0.736
Ne
He
0.231(4)
0.249
P
< 0.00007
0.00001
C
0.009(2)
0.0029
S
0.00091(6)
0.00050
N
< 0.012
0.00085
Ar
< 0.00015
0.00007
O
< 0.0035
0.0057
“Z”
0.027
0.015
0.00023(3)
0.0018
Jupiter – King of the Planets
Mass = 0.001 solar (318 Earth masses),
Radius = 10.5 … 11.2 Earth radii,
Density = 1.3 g/cc (1.3 x water)
Distance: 5.2AU
Orbital Period: 11.8 years
Rotation period: 9:55 hours.
10.5 RE
11.2 RE
Flattened Spheroid
Saturn
Mass = 95 Earths (only 30% of Jupiter)
Radius = 9.4 Earths
Density = 0.7 gram/cm3 (floats)
Distance: 9.5 AU
Orbital Period: 29.4 years
Rotation period: 10.6 hours.
Rings: Composed of billions of icy rocks and
icy dust particles (water ice and silicates).
Interior of Jupiter and Saturn
“Phases” of Hydrogen:
The Interiors of Jupiter & Saturn
Phases of Hydrogen
Density
Computer Simulation:
Molecular and Metallic hydrogen
Molecular
hydrogen
•Electrons bound to molecules
Metallic
hydrogen
•Electrons free to move
“Phases” of Hydrogen:
The Interiors of Jupiter & Saturn
Phases of Hydrogen
Density
A New Probe of Jupiter: “Juno”
Launch August 5, 2011
Interior of Jupiter
A New Probe: “Juno”
Surfaces of the
Giant Planets
Jupiter
Jupiter’s Atmospheric Properties
Rotation Period = 9 hours 55 minutes
(based on Jupiter’s magnetic field)
Rotation Period = 9 hours 55 minutes
(based on Jupiter’s magnetic field)
Cassini (2000)
Jupiter’s Atmosphere
Jupiter’s Atmosphere
Convection on Jupiter:
Bands of Jupiter
What Causes them?
•Warm air rises
•Coriolis force
diverts path sideways
Coriolis force is due to
rotation of planet
•Jupiter rotates fast:
Period = 10 hours
Winds of Jupiter’s Bands
Red Spot
in Southern
Hemisphere
Great Red Spot
A Hurricane that has
lasted 300 years
Giant red spot in motion
Giant red spot in motion
Red Oval in motion
Red Oval in motion
Cyclones and Anticyclones
on Jupiter
Computer Simulation of
Cyclone Formation
Red Spot Jr. spot formed
from three white ovals and
later turned red.
Cyclonic Motions
Southern
Hemisphere
Northern
Hemisphere
Coriolis effect:
Motion from
High Pressure area
Comparison of Cyclones and Anti-Cyclones
Cyclones:
Anti-Cyclones:
•
•
•
•
•
•
•
•
•
Low pressure weather phenomena,
Winds blow inwards,
Typical storm systems on Earth
Rotate counter-clockwise on Northern
hemisphere,
• Rotate on clockwise on Southern hemisphere,
High-pressure weather phenomena,
Winds blow outwards,
Example: Jupiter’s red spot
Rotate clockwise on Northern hemisphere,
Rotate counter-clockwise on Southern
hemisphere,
What is this?
(A)
(B)
(C)
(D)
Anti-cyclone on northern HS
Cyclone on the northern HS
Anti-cyclone on the southern HS
Cyclone on the southern HS
Comparison of Cyclones and Anti-Cyclones
Cyclones:
Anti-Cyclones:
•
•
•
•
•
•
•
•
•
Low pressure weather phenomena,
Winds blow inwards,
Typical storm systems on Earth
Rotate counter-clockwise on Northern
hemisphere,
• Rotate on clockwise on Southern hemisphere,
High-pressure weather phenomena,
Winds blow outwards,
Example: Jupiter’s red spot
Rotate clockwise on Northern hemisphere,
Rotate counter-clockwise on Southern
hemisphere,
What is this?
(A)
(B)
(C)
(D)
Anti-cyclone on northern HS
Cyclone on the northern HS
Anti-cyclone on the southern HS
Cyclone on the southern HS
Jovian Storms
Red Spot: A High Pressure Storm
• Analogous to hurricanes (low pressure systems, material flows in), but they rotate in
the opposite direction because they high pressure systems where material flow out
Jupiter
• the Great Red Spot
• we are not sure why it is red
Neptune
• the Great Dark Spot
Planet
Rotation
Uranus – Haze but any Clouds?
Mass = 14.5 Earths
Radius = 4.0 Earths
Density = 1.3 gram/cm3 = 1.3 x water
Distance: 19.2 AU
Visible Light
Featureless in visible light, because clouds are below
haze layer of methane (colder than Saturn).
Orbital Period: 84 years;
Rotation period: 17.2 hours.
Infrared Light (Thermal Emission)
Uranus – Yes Plenty of Clouds
Visible Light
•Featureless in visible light, because clouds
are below haze layer of methane (colder than Saturn).
Uranus – Yes Plenty of Clouds
Neptune
Mass = 17 Earths
Radius = 3.9 Earths
Density = 1.76 x water
Distance: 30 AU
Orbital Period: 163 years;
Rotation period: 16.1 hours.
Cyclonic storms.
Uranus & Neptune
Giants of H, He, and Water!
Gaseous envelope of
H, He, and some CH4
Liquid mixture of
H2O, CH4, NH3 ices
Rocky core (silicates+iron)
Hydrostatic Equilibrium: Pressure balance
Pressure at any depth = gravitational weight of column above
“Hydrostatic equilibrium” governs the structure of all planets.
The inside has higher pressure and density because of the weight of
the overlying material.
Inside Giant Planets
Saturn emits almost twice as much energy as it absorbs from the Sun.
• Neither Cooling nor Radioactivity can account for it
• Saturn must a different “secret” heat source
Jupiter has 3x more mass than Saturn, but is only slightly larger in radius!
• the added weight of H & He compresses the gases below to a higher density
• like stacking pillows
• If Jupiter had 10x its mass,
it would have same radius !
Add even more mass, and
Jupiter would get smaller !
• Jupiter is as large as a planet
can get.
• Uranus & Neptune have
less mass than Saturn, yet
they have higher densities
• They must be made of
denser material:
More Rock & Water !
Determining the Density inside a Rotating Planet
Use Motion of Orbiting Satellites
Rotation flattens shape —> Less pull on satellite at poles
Higher density
toward center
Track acceleration of
satellites accurately
—> Exerts Point-like Gravitational Force
—> Density profile throughout interior
Interactive Quiz
How would you land on Jupiter?
(A)With parachutes
(B) With thrust rockets
(C) With pontoons like a seaplane
(D) You cannot land on Jupiter.
Interactive Quiz
How would you land on Jupiter?
(A)With parachutes
(B) With thrust rockets
(C) With pontoons like a seaplane
(D) You cannot land on Jupiter.
Thursday’s Lecture:
Moons orbiting the Giant Planets
A volcanic explosion
can be seen
silhouetted against
dark space over Io's
brilliant limb. Io more
volcanically active
than Earth.
How many Jovian
moons are there?
Jupiter’s Moon: Io
Jupiter – King of the Planets
Radius = 10.5 … 11.2 Earth radii
Make a bigger Earth that has a radius 10 times
larger. Assume the density would be the same,
what would its mass be?
(A)The same, one Earth mass
(B) 10 Earth masses
(C) 100 Earth masses
(D) 1000 Earth masses
Jupiter – King of the Planets
Radius = 10.5 … 11.2 Earth radii
Make a bigger Earth that has a radius 10 times
larger. Assume the density would be the same,
what would its mass be?
(A)The same, one Earth mass
(B) 10 Earth masses
But Jupiter’s mass is only
(C) 100 Earth masses 318 Earth masses. What does
(D) 1000 Earth masses this tell us?
Size of Rocky Planets
Make the Earth a 1000 times more
massive. How large would its radius be?
(A)The same, one Earth radius
(B) 3 Earth radii
(C) 6 Earth radii
(D) 10 Earth radii
Size of Rocky Planets
Make the Earth a 1000 times more
massive. How large would its radius be?
(A)The same, one Earth radius
(B) 3 Earth radii (because of gravity!!)
(C) 6 Earth radii
(D) 10 Earth radii
Neptune’s
Storms
scooter
Altitude above clouds tops (km)
Jupiter’s Cloud Layers
Convection in the troposphere causes
Jovian weather.
Warm gas rises to cooler altitudes, where it
condenses to form clouds.
Three gases condense in the Jovian
atmosphere:
• ammonia (NH3) (high altitude)
• ammonium hydrosulfide (NH4SH)
• water (H2O)
They condense at different temperatures, so
their clouds form at different altitudes.
Temperature (°C)
The Jovian Atmospheres
The temperature profile of each planet
determines the color of its appearance.
Cloud layers form where a particular
gas condenses.
Saturn has the same cloud layers as
Jupiter.
• they form deeper since Saturn is
colder overall
• they are spread farther apart since
Saturn has lower gravity
Uranus & Neptune
• cold enough to form methane clouds
Aurora Borealis near Jupiter’s North Pole
Auroral Zones
The high energy particles come down the magnetic field lines and
hit the atmosphere near the poles, causing the gases to glow. Just
like on the Earth, this makes an “aurora” in a ring-like zone.
Jupiter
Uranus
Magnetic Fields
Neptune
Saturn
Jupiter’s Magnetosphere –
Bigger than the Sun
Solar Wind
protons &
electrons
Jovian Magnetospheres
Saturn, Uranus, & Neptune have smaller & weaker magnetospheres.
• fraction of electrically conducting material in interiors is smaller
• Solar wind is weaker farther out, or else their magnetospheres would be even smaller
• we can not explain the magnetic field tilts of Uranus & Neptune.
Quiz
If Jupiter formed in a protoplanetary disk
that had twice as much dust in it:
(A) Would have a bigger core
(B) Might have more hydrogen
(C) Might have more metallic hydrogen
(D) All of the above
Quiz
If Jupiter formed in a protoplanetary disk
that had twice as much dust it:
(A) Would have a bigger core
(B) Might have more hydrogen
(C) Might have more metallic hydrogen
(D) All of the above
Why are the Jovian Planets
Massive and Gaseous (H, He) ?
Formed beyond the frost line (3 AU):
so cold that ice particles exist with silicate dust.
Ice and Dust collides, sticks grows into icy-rocky core.
Core’s gravity captures H/He gas
Planet attracts ices and dust that orbit
Moons formed out of these disks: A miniature solar system.
Young Solar System:
Gas & Dust
Young Jupiter