Transcript The Outer Planets

The Outer Planets
and Their Moons
Essential Questions
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3.
What characteristics do the outer planets have
in common?
What characteristics distinguish each of the
outer planets?
Should Pluto be reinstated as a planet?
The Gas Giants
Jupiter
Saturn
Neptune
Uranus
The Outer Planets
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Much larger and more massive than the inner planets
Do not have solid surfaces
All are composed mainly of hydrogen & helium
More gravity than Earth due to their high mass
Thick atmospheres with high atmospheric pressure
A lot of the hydrogen & helium inside the planets is liquid
because of enormous pressure
Outer layers of the planets are cold because of their
distance from the sun, but temperatures increase inside
the planets
All have many moons
All have rings composed of small particles of ice and
rock
“Gas Giants”
Like the sun, the gas giants
are composed mainly of
hydrogen and helium.
Because they are so
massive, the gas giants
exert a much stronger
gravitational force than the
terrestrial planets. These
planets have thick
atmospheres because
gravity keeps these gases
from escaping into space.
Multiple Moons and Rings
All of the gas giants have many moons and are surrounded
by a set of rings. A ring is a thin disc of small particles of
ice and rock.
MULTIPLE MOONS
RINGS
Jupiter
Jupiter
• Named for the Roman king of all gods, because
other than the Sun, it’s the largest object in our
solar system.
Jupiter
The largest planet with the most mass
 Mass is about 2 ½ times all other planets
combined
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Jupiter’s
Atmosphere
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Thick atmosphere of mainly
hydrogen & helium, with
some methane, ammonia,
water, and sulfur compounds
The Great Red Spot – a
giant storm large enough to
fit two Earth’s side by side.
 Hurricane-like winds
blow hundreds of miles
an hour
 it has lasted for 350
years
 The lack of terrain
features prevents the
storm from weakening.
Jupiter’s Atmosphere – Differential Rotation
The cloud speeds on Jupiter vary with latitude, an effect
called differential rotation. Near the poles, the rotation
period of Jupiter’s atmosphere is five minutes longer
than that at the equator.
POLAR REGION
ROTATION TIME
9 hours 55minutes
EQUATORIAL REGION
ROTATION TIME
9hours 50minutes
Jupiter’s clouds move in east-west bands
Reddish-colored belts alternate with white-colored zones.
Jupiter’s Atmosphere – Color Belts
Astronomers believe that the belts and zones are
created by a combination of the planet’s convection
and its rapid differential rotation.
Jupiter’s Structure
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A dense core of rock and
iron at the center
The core is surrounded by a
thick mantle of liquid
hydrogen & helium
Pressure at Jupiter’s core
may be 30 million times
greater than the pressure at
Earth’s surface
Extreme pressure is caused
by its thick atmosphere
Jupiter’s Internal Sources of Energy
• Gravitational compression causes Jupiter to radiate
more heat than it absorbs from the sun.
• Heat is probably left over from the original collapse of
the primordial nebula to form the Solar System
• internal heat source drives the complex weather
patterns in its atmosphere, unlike the Earth where the
primary heat source driving the weather is the Sun.
Jupiter’s Moons
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Galileo discovered Jupiter’s largest four moons
in 1610 (Galilean moons)
Many more have been discovered as technology
improved – latest count is 63
The four largest are very different from each
other
Jupiter’s Largest Moons
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Io – its surface is covered with large, active
volcanoes. Sulfur gives it a yellow-orange color.
Europa – it has an icy crust an ocean of liquid water
underneath the ice. NASA is planning an unmanned
mission to look for conditions that would support life.
Ganymede – the largest moon in the solar system is
larger than Mercury or Pluto. Water was recently
discovered beneath its icy surface. It actually has
more water than Earth does! Is life possible?
Callisto – has an icy, highly-cratered surface. It’s
the most cratered object in our solar sysem
Saturn
Saturn Statistics
Named for the Roman
god of the harvest and
agriculture
Mass:
5.7 x 1026 kg
Volume:
8.3 x 1014 km3
Diameter:
116,464 km
Density:
0.687 g/cm3
Escape velocity:
35.5 km/s
Surface gravity:
10.44 m/s2
Moons:
60
Orbit period:
10,759.22 days
Avg. Dist. to Sun: 1.4 x 109 km
Avg. orbital velocity: 9.69 km/s
Length of day:
10.66 hours
Axial tilt:
26.73°
Saturn
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The second-largest planet
Has a thick atmosphere of hydrogen & helium
Atmosphere has thick clouds and storms – though not as
spectacular as those on Jupiter
The least dense planet (less dense than water)
The Voyager probes provided lots of information about
Saturn
Saturn’s Rings
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Saturn has the most spectacular rings of any
planet
 The rings are broad and thin – like a CD
 The rings are made of chunks of ice and rock,
each traveling in its own orbit around Saturn
Saturn’s Moons
Saturn is currently known to have more
than 60 moons
 The largest is Titan
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It has a very thick atmosphere (so thick that
light can hardly pass through)
There are four other moons that are larger
than 1,000 kilometers in diameter
Saturn’s Moons
TITAN:
 Saturn’s largest moon
 Second largest moon in
the solar system
 Has a dense nitrogen
atmosphere
 Surface Pressure: 1.6
atm
 Similar in conditions to
early Earth
Titan’s Primordial Soup?
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Titan is a complex moon that is more similar to a
terrestrial planet than a typical outer planet moon.
Titan's orbit carries it in and out of Saturn's
magnetosphere
Methane in the atmosphere reacts with sunlight to
produce a hydrocarbon smog
Titan's hidden surface may have exotic features:
mountains sculpted by hydrocarbon rain, rivers, lakes
and "waterfalls" of flammable liquids
Water and ammonia magma may occasionally erupt,
spreading across the surface, creating exotic
landscapes
Two views of Titan
From Far Away
Very Close Up with
special Lens
Saturn’s Moons
MIMAS:
 Has an impact crater
that is 1/3 the
diameter of the
satellite
 Biggest impact Mimas
could have taken and
still survived
“That’s no moon”. – Obi-Wan Kenobi
(But it is!)
Saturn’s Moons
PHOEBE:
 Discovered in 1898
 First retrograde
satellite known in
the solar system
 Most likely a
captured satellite
 Saturn’s outermost
moon
Saturn’s Moons
Iapetus:
 Along its orbit, it picks up
dark dust from Phoebe
 Like our moon, the same
side faces Saturn at all
times (synchronous
rotation)
 Because of the dust, it’s
leading face is dimmer than
its trailing face
Saturn’s Moons
Hyperion:
 Only satellite in the
solar system that is
not in synchronous
orbit
 Not spherical
 Probably a remnant of
a larger moon that
was destroyed
Saturn’s Moons
Enceladus:
 500 km in diameter
 Covered with water ice
 Heavily cratered in the
northern hemisphere
 Geologically active
 Ice geysers supplied
material for the E-Ring
Uranus
Uranus Facts
Discoverer:
Sir William Hershel (1781)
Spacecraft Encounter(s):
Voyager 2 (1986)
Mean distance from Sun:
19.19 AU (2.871 billion km/1.784 billion mi)
Length of year:
84.01 Earth years
Rotation period:
17.24 hours
Mean orbital velocity:
6.81 km/s (4.2 m/s)
Inclination of axis:
97.92°
Diameter:
Number of Observed
Satellites:
51,118 km
>20
Diameter:
4.0 x Earth's
Mean Distance from Sun:
19.2 x Earth's
Mass:
14.5 x Earth's
Density:
0.22 x Earth's
The picture on the right uses false colors and
contrast enhancement to bring out subtle details
in the polar region of Uranus.
Uranus
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Uranus is named for the Greek
god of the sky
It is about four times the
diameter of Earth, but much
smaller than Jupiter and Saturn
It is twice as far from the sun as
Saturn, so it is much colder
Has a unique blue-green color
because of methane gas in its
atmosphere
Its rings are thin, flat, and much
darker than Saturn’s
Discovered in 1781 by Willam
Herschel in England, and is the
first planet that was discovered
after ancient times.
Uranus
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In the 1980s (200 years after
being discovered) Voyager 2
arrived at Uranus and sent back
close-up pictures
It has few clouds, but
astronomers calculated it rotated
in about 17 hours
Uranus is tilted on its side
 It rotated top to bottom instead
of side to side like other
planets (and its rings and
moons rotate around its tilted
axis)
 Scientists think it was hit by an
object billions of years ago
that knocked it on its side
Uranus’s Moons
Uranus has at least 27 moons
 Voyager 2 discovered the five largest
moons have icy, cratered surfaces and
lava flows
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Neptune
Neptune Facts
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About 4 times diameter of Earth- a
bit smaller than Uranus
4.5 billion km (2.8 billion miles)
from Sun
Period of revolution is 165 years
Rotation period is 18 hours
One large satellite (2700 km),
seven smaller ones
Four narrow rings
Named after the Roman god of the
sea
• Very cold, -225° C (-373° F)
• Gravitational compression
produces more internal heat than
it absorbs from the sun.
• The blue-green color of the
planet is due to the presence of
methane in the atmosphere.
• The atmosphere consists mostly
of hydrogen, helium and
methane.
• rings completely circle the planet,
but the thickness of each ring
varies along its length.
Neptune
Neptune’s Great Dark Spot
• a great storm in the southern
hemisphere called the “Great
Dark Spot" is about half the size
of Jupiter's Great Red Spot
• Spot is about the same diameter
as the Earth
• at least one other smaller storm
spot has been detected.
• Neptune has the fastest
planetary winds in the Solar
System, reaching as fast as
2,000 km (over 1,200 miles) per
hour.
Neptune
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Neptune is similar in size and
color to Uranus
It is a blue color because of
methane in its atmosphere
Because it is so far from the
sun, it is very cold
It has clouds and storms in its
atmosphere
 Scientists think the clouds
and storms are happening
because the planet is slowly
shrinking, causing the
interior to heat up
Discovering Neptune
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Neptune was discovered by
mathematics
 astronomers noticed
Uranus’s orbit wasn’t the
exact path it should be and
predicted an unseen
planet was disturbing
Uranus’s orbit
 By 1846 scientists had
calculated the orbit of the
unseen planet – soon
after, Neptune was
identified
Flying by Neptune
In 1989 Voyager 2 flew by Neptune and
photographed the Great Dark Spot (a
storm about the size of Earth)
 Storms come and go on Neptune which
tells us it has an active atmosphere
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Neptune’s Moons
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Neptune has at least
13 moons
The largest is Triton
 It has a thin
atmosphere
 Its south pole is
covered in nitrogen
ice
Dwarf Planets
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Dwarf planets are round and orbits the sun, like a planet,
but it has not cleared out the neighborhood around its
orbit
Dwarf planet classification was created in 2006 when an
object larger than Pluto and farther from the sun was
discovered
At that time Pluto was reclassified as a dwarf planet and
there are two others
Pluto
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Pluto is a dwarf planet
It is much smaller and denser than the outer planets and has
a solid surface
Pluto is smaller than our Moon
Pluto is so far from the sun that it takes 240 Earth years to
revolve around the sun once
 This means that, since its discovery, Pluto hasn’t made a
full revolution yet!
 Its orbit is very elliptical and it crosses inside Neptune’s
orbit for part of its revolution
Moons
 Pluto has five moons. The largest is Charon and is more
than half as big as Pluto
Essential Questions - Answered
1.
What characteristics do the gas giants
have in common?
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No solid surface
Thick atmosphere made mostly of hydrogen
& helium
A set of rings
Very Large & massive
Rotates quickly, revolves slowly
2.
What characteristics distinguish each of
the outer planets?
Jupiter – largest & most massive planet, Great
Red Spot, most moons (63+)
Saturn – second largest planets, best rings,
least dense planet
Uranus – blue-green color, rotates on its side
Neptune – blue color, lots of storms
Pluto – solid, rocky surface; no longer a planet