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Chapter 28
Copyright (c) The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Uranus
The Discovery of Uranus
• In 1781 a new
planet was
discovered by
W. Herschel
– And his sister
Caroline
– Originally
thought to be
a comet!
The Discovery of Uranus
Herschel named it:
Georgium Sidus
(George’s Star) after
King George III
– Name changed
to Uranus to
stay consistent
with the
mythological
names of the
other planets
Uranus
Size: 31,763.16
miles
Rotation is: 17
hours; 14 min
(~retrograde)
Revolution: 84 yrs
Distance from Sun:
19.191 AU
1,782,000,000 miles
The Discovery of Uranus
Incline plane is 0.8
Gravity: 0.92
If you weigh 150
pounds on earth
you would
weight ?
But its TILT is the
most notable
feature…
Uranus’s Axial Tilt
Uranus it tilted 98
degrees on its
side
Thus the planet
receives sunlight
overhead for
years at time at
either pole while
the quarter
receives almost
NO sunlight…
Uranus’s Axial Tilt
• Uranus is tipped 98 degrees to the ecliptic plane
• Possible that a collision early in its history
tipped the axis, and splashed out material for its
moons
Uranus’s Axial Tilt
• This inclination means that for half of
Uranus’ orbit, one hemisphere is in
uninterrupted daylight, and the other
hemisphere is in darkness!
• The atmospheres of both Uranus and
Neptune are rich in hydrogen and
helium
– Both have larger amounts of
methane, giving them their blue
color
The Atmospheres of
Uranus and Neptune
• The atmospheres of both Uranus and
Neptune are rich in hydrogen and
helium
– Methane crystals scatter blue light,
and methane gas absorbs red light
The Atmospheres of
Uranus and Neptune
The Atmospheres of
Uranus and Neptune
• Both planets are
very cold
– Uranus: 80K
– Neptune: 75K
• Densities:
– Uranus: 1.3
kg/liter
– Neptune: 1.6
kg/liter
The Atmospheres of
Uranus and Neptune
Their interiors
are probably
ordinary water
mixed with
methane and
ammonia,
surrounding a
core of rock
and iron-rich
material
Odd Magnetic Fields
• Both Uranus and
Neptune have
magnetic fields
– Stronger than
Earth’s
• Uranus: 47x
• Neptune: 25x
Odd Magnetic Fields
• Sounds from the
Planet Uranus
https://www.youtube.
com/watch?v=h1yCcs
A-KCs
Odd Magnetic Fields
• Both Uranus and
Neptune probably
generate currents
in the liquid water
in their interiors
– Tipped in odd
directions!
– Not centered on
the center of the
planet, as with
Earth, Jupiter
and Saturn
All of the Gas Giants
Have Ring Systems
Uranus just like the
gas giants also has a
ring system. Uranus
has 11 of them faint
and small in size.
• Composition is mostly
small icy particles and
rocky debris from
rubble piles.
• Maybe from the
breakup of satellites.
Satellites of Uranus
Satellites of the giant planets range in size from larger
than Mercury to small asteroid-like bodies
Some of the satellites are in regular orbits Satellites of Uranus
(nearly circular, orbiting in the same direction that the
planet spins, and near the planet’s equator) which
probably formed along with the planet.
Satellites of Uranus
• Many of the orbits are irregular, and the satellites appear
to be captured bodies
Satellites of Uranus
Uranus has
27 Moons.
Here are the
top five
Most moons are made of ice and rock
and some appear to be captured
asteroids due to their size and orbits.
Satellites of Uranus
Satellites of Uranus
Most of the moons,
including Titania, Oberon,
and Umbriel, seem to be
"normal" moons without
anything interesting;
Satellites of Uranus
However, Miranda and
Ariel seem to have had
violent pasts. Let us look
at them.
Uranus’s Moon Miranda
Miranda is the
smallest of Uranus'
moons that is
visible from
the Earth.
Rotation/ Rev is
1.47 days
Ave Temp: -335° F
Uranus’s Moon Miranda
• Miranda appears to
have been shattered
by an impact, and
is still putting itself
back together
– Long cracks or
faults riddle its
surface
– Rolling hills
adjacent to
wrinkled terrain
20 km tall cliffs on Miranda
Largest cliffs (12
miles) in the Solar
system
That is 8 times
depth of grand
canyon
If you based
jumped you would
free fall for 9
minutes before
hitting the ground.
Uranus’s Moon Miranda
• If this were scaled to be on Earth, it would reach into the
orbit of spacecraft.
• It also has three long, rectangular shapes, called
"coronae.
Uranus’s Moon Miranda
• Scientists think that at one time the pull of the other
moons warmed the interior and caused the ice in
Miranda to start to rise. The coronae mark where it
froze before coming to the surface.
Uranus’s Moon Ariel
• Ariel is covered with complex fractures and grooves.
• Rotation/ Rev is 2.52 days
• Ave Temp: -338° F
Uranus’s Moon Miranda
• Probably they are the result of ice seeping to the surface,
then freezing and expanding.
• Ariel also has lava-filled valleys. The lava is made of a
mixture of water and liquid ammonia
Unit 44
Neptune
Copyright (c) The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
A New Method of Discovery
• It was noted that Uranus was not following its
calculated orbit
– Another planet must be influencing its orbit
– 1845 Two scientists, John Adams (1819-1892)
(English) & Urbain Le Verrier (1811-1877)
(French) calculated where the new planet should
be based on its effects on Uranus using Orbital
Calculations.
A New Method of Discovery
• Astronomers looked at this location, and
found…
NOTHING!!!
A New Method of Discovery
Then in 1846 Astronomers Gottfried Galle (1812-
1910 German) & Heinrich Louis d’Arrest (18221875 Danish) looked around the location again, and
found… Neptune!
A New Method of Discovery
Galileo saw Neptune while looking at Jupiter’s
moons, but didn’t realize what it was… he
thought is was a comet
Neptune
NEPTUNE:
Rotates: 16 hrs/ 03
min
Revolves 164.8 yrs
DISTANCE:
30.061 AU
2,793,000,000 miles
size: 30,707.36
miles
• The atmospheres of
both Uranus and
Neptune are rich in
hydrogen and
helium
– Both have larger
amounts of
methane, giving
them their blue
color
– Methane crystals
scatter blue light,
and methane gas
absorbs red light
The Atmospheres of
Uranus and Neptune
The Atmospheres of
Uranus and Neptune
Their interiors are
probably
ordinary water
mixed with
methane and
ammonia,
surrounding a
core of rock and
iron-rich
material
• Neptune is
very cold
– Neptune:
75K
• Densities:
– Neptune:
1.6 kg/liter
The Atmospheres of
Uranus and Neptune
The Atmospheres of
Uranus and Neptune
Their interiors are
probably
ordinary water
mixed with
methane and
ammonia,
surrounding a
core of rock and
iron-rich
material
Odd Magnetic Fields
• Both Uranus and
Neptune have
magnetic fields
– Stronger than
Earth’s
• Uranus: 47x
• Neptune: 25x
Odd Magnetic Fields
• Sounds from the
Planet Uranus
https://www.youtube.
com/watch?v=rwnpX
ll_A_E
Storms
• High winds lead
to storms on
Neptune
• Fastest winds
in the solar
system over
1000mph
Storms
• Like Jupiter,
Neptune also has
a giant hurricane
• The Great Dark
Spot, which
disappeared
recently but has
since returned
Uranus’s Axial Tilt
Neptune is tilted 30
degrees
All of the Gas Giants
Have Ring Systems
Neptune also has a
ring system.
Neptune’s 4 rings.
Outer most is called: Adam
Contains 3 prominent arcs which are now named
Liberty, Equality, and Fraternity
The next ring, closest to Adam, is an unnamed ring.
After that, there is Leverrier
Which has outer extensions called Lassell and Arago
Lastly, there is the faint ring Galle
Which is 42,000 kilometers away,
The closest ring to Neptune
Satellites of Neptune
Neptune has
13 Moons.
The only
interesting
one is
TRITON
Neptune’s Moon Triton
Triton
– 3728 miles
– Triton is larger
than Pluto and
almost as big as
Europa
Neptune’s Moon Triton
Rotation/ Rev: 5.87
days
Its orbit is backwards
relative to
Neptune’s rotation
RETROGRADE
This is likely a
captured icy
planetesimal
Neptune’s Moon Triton
Its on a collision
course with
Neptune and
will provide raw
material for a
future
Neptunian ring.
Neptune’s Moon Triton
Triton
– Triton has a
surface of mostly
frozen nitrogen, a
mostly water
ice crust,
– an icy mantle
– and a substantial
core of rock and
metal.
Neptune’s Moon Triton
Triton has an
atmosphere
that freezes out
on the night
side of the
planet.
It also has odd
surface
features.
Triton
– Triton is one of
the few moons in
the Solar System
known to be
geologically
active.
Triton
As a consequence, its
surface is relatively
young, with a complex
geological history
revealed in intricate
and mysterious
kryovolcanic and
tectonic terrains.
Neptune’s Moon Triton
Triton
– Part of its crust is dotted
with geysers thought to
erupt nitrogen. Triton has
a tenuous nitrogen
atmosphere less than
1/70,000 the pressure of
Earth's atmosphere at sea
level
Beyond Neptune
According to the International Astronomical Union this is
this ends the Major planets.
SO what is beyond Neptune?
Beyond Neptune
Something called: Trans –Neptunian Objects
These objects (known as TNO) are nearly the
same size as Pluto and are beyond Neptune's
orbit
Most TNO come from a second area that
is just beyond Neptune called:
Beyond Neptune
And that is another story