Download 11.2b The Solar System Asteroids and Gas Giants

The Asteroids
and Gas Giant
Planets
The Asteroid Belt
Between Mars and Jupiter is a belt of rocky materials orbiting
the sun. They range in size from 950 km in diameter (Ceres –
could it be classified as a planet?) to just fractions of a meter.
There are over 200 asteroids that have a diameter of 100 km
or more. There are 1.7 million asteroids with a diameter of 1
km or more.
The Origin of the Asteroid Belt
A number of theories exist about what caused the asteroid
belt. The one most favoured today is that the asteroids
would have clumped together into another terrestrial planet
but the planet Jupiter was too close and its large gravity
force prevented the asteroids from clumping together and
instead made them collide and break into more pieces.
Three Different Kinds of Asteroid
Asteroids tend to be metallic or silicate (rocky or glassy with
the element silicon) or carbonaceous (like carbonates –
carbon and oxygen) in composition.
Metallic
Silicate
Carbonaceous
The Asteroid Belt : Low Density
Asteroids are spaced very far apart. Nine spacecraft have
been sent through the belt without any collision. It is
calculated that there is a one in a billion chance of hitting an
asteroid when sending spacecraft through the belt.
The Largest Asteroids
The asteroid Ceres may be a planet with a diameter of 950
km. 4 Vesta has a diameter of 529 km and 2 Pallas has a
diameter of 544 km.
The Hazards of Asteroids
The planet, Jupiter, is able to disturb the orbits of asteroids
which then may collide and change their path of motion.
Some asteroids may take a path that goes towards Earth and
if large enough may collide with Earth, causing limited or
extensive damage to living things.
Jupiter
Jupiter, the first of the Gas Giant planets, is the largest
planet, having a mass that is 2.5 X more than all the other
planets combined (318 X Earth’s mass). Jupiter’s “Great Red
Spot” is a storm (the size of three Earths) raging in the
clouds of hydrogen and helium on the outer surface of the
planet.
Jupiter : Almost Became a Star
If Jupiter had come from a nebula that had 100 X more mass,
it would have become a small star. Jupiter emits as much
radiation and heat as it receives from the sun. The
temperature of Jupiter’s core is 35,700 C.
sunlight
Jupiter light
Jupiter’s Revolution and Rotation
Jupiter takes 12 Earth years for one revolution around the
sun. It rotates one every 10 hours. At its equator, Jupiter is
traveling at 35,200 km/h (Earth’s equator is traveling at 1670
km/h).
Jupiter’s Composition and Structure
Jupiter’s is mostly
made up of
hydrogen with
some helium. It’s
atmosphere is 75%
hydrogen and 25%
helium. Jupiter is
thought to have a
solid core
surrounded by
liquid metallic
hydrogen with an
outer layer of
gaseous molecular
hydrogen.
Jupiter’s Rings
With Earth-based telescopes, Jupiter’s very thin rings of dust
can not be seen. Space probes flying past Jupiter sent
pictures of Jupiter’s rings back to Earth.
Jupiter’s Surface, Gravity and Temperature
Jupiter has no defined surface as its outer gases merge with
the liquid layer below. The gravity of Jupiter at its outer
clouds is 2.4 X the gravity of Earth, increasing up to 318 X as
one passes deeper through its clouds. Jupiter’s temperature
at its outer clouds is -110 C and rises to 35,700 in its core.
Jupiter’s Magnetic Field
Jupiter has a magnetic field that deflects and traps solar wind
particles.
Jupiter’s Moons
From a simple Earth telescope, four moons of Jupiter can be
seen. These are called the Galilean moons since Galileo in
the 1600s was the first to record their existence. We now
know that Jupiter has 63 moons of various sizes.
Jupiter’s Moon, Io
Io is a very active moon with sulfur (yellow) lava flows, lava
lakes, 500 km high sulfur geysers and volcanoes and 16 km
high mountains.
Jupiter Moons : Europa, Callisto and Ganymede
Europa has a smooth icy crust. Callisto is heavily cratered
with a 200 km crust lying over a salty ocean beneath.
Ganymede is the largest moon of Jupiter and our Solar
System. Ganymede would be a planet if it were orbiting the
sun.
Saturn
The rings of Saturn, composed of ices rather than rocks, are
easily seen with telescopes on Earth. Saturn is about 95 X as
massive as the Earth.
Saturn’s Revolution and Rotation Rate
Saturn takes 29.5 Earth days for one revolution around the
sun. Saturn revolves around once in 10 hours and 40
minutes.
Saturn’s Composition and Structure
Saturn is 96% hydrogen and 4% helium. It has an inner rock
core surrounded by liquid metallic hydrogen and an outer
layer of liquid molecular hydrogen.
Saturn’s Surface
Like Jupiter, Saturn has no definite surface. Its outer clouds
merge with the outer liquid molecular hydrogen layer. The
temperature of the outer clouds is -178 C and warms up to
11 700 C in the core. Saturn radiates out 2.5 X as much
energy as it receives from the sun. Storms and winds up to
1 800 km/h sweep across Saturn’s surface.
sun radiation
Saturn radiation
Saturn’s Magnetic Field
Saturn has a magnetic field that is slightly weaker than the
Earth and helps to deflect solar wind particles.
Saturn’s Rings
Saturn has a very large and complex ring structure. The
rings are very thin in comparison to their width. The rings
are made up of dust and ice with few rocks. The rings may
be remnants of the nebula that formed Saturn or the remains
of a moon(s) that disintegrated.
Saturn’s Moons
Saturn has 62 moons, five which are very large. Titan, the
second largest moon in our Solar System, is larger than the
planet Mercury but is a moon because it is orbiting a planet.
The Saturn Moon Titan
Saturn’s moon, Titan, has an
atmosphere made up of nitrogen and
hydrocarbons that is denser than
Earth’s atmosphere. It appears to
have lakes and rivers of ethane and
methane.
The Saturn Moon Enceladus
Enceladus is ice covered. Water spouts have been observed
near its south pole, probably due to interior heat within the
moon.
Uranus
The Gas Giant
(Sometimes called an
Ice Giant), Uranus, is
similar in composition
to Jupiter and Saturn
and also has rings. It
has a mass that is 14.5
X that of Earth.
Uranus’ axis of
rotation is
pointed towards
the sun so one
pole is in light 42
years while the
other pole is in
the dark for 42
years. Near the
equator, days are
8.5 h long
followed by 8.5 h
nights. Uranus’
equator is hotter
than its poles,
something
unexpected since
its poles get
more sunlight.
Uranus
Revolution and Rotation of Uranus
It takes 84 Earth years
for Uranus to make one
revolution of the sun.
Uranus rotates once in
17 Earth hours and 14
minutes.
Uranus Composition and Structure
Uranus is composed mostly of hydrogen, helium, and ices of
water, ammonia and methane. Uranus has small icy/rocky core, a
hot fluid mantle and gas atmosphere that is 83% hydrogen, 15%
helium and 2 % methane. The methane gas is mostly in the upper
atmosphere and gives the planet a blue look because it absorbs
red from the sunlight falling on it. The hot liquid mantle generates
electric currents, helping make the planet’s magnetic field.
Uranus’ Surface
Winds up to 900 km/h have been observed on the outside
clouds surrounding Uranus. The surface has an average
temperature of -224 C while its core has a temperature of
5000 C.
Uranus’ Magnetosphere
Uranus has a magnetic field that protects its atmosphere
from solar wind particles.
Uranus’
Rings
The thin
and dark
rings of
Uranus
are made
up of
dust and
ices.
Uranus’ Moons
Uranus has 27 moons. Many are heavily cratered, a number
have deep rift valleys and faults that point to movement of
moon parts. Umbriel has a spot called the florescent cheerio
(probably a crater).
Uranus Seen
From One of
its Moons
This is an
artist’s
conception of
a view of
Uranus from
one of its
moons.
Neptune
The planet Neptune is 17 X Earth’s mass and is on average at
a distance of 30 AU from the sun. It takes 165 years to
revolve once around the sun and takes 16.11 hours to rotate
once. Neptune’s surface has a temperature of -200 C.
Neptune’s Tilted Axis Gives it Seasons
Neptune’s axis of rotation is tilted at 28 degrees which
produces seasons. Each season (Spring, Summer, Fall and
Winter) of Neptune lasts for about 40 Earth years.
Neptune Structure
Neptune has a structure much like Uranus. The core is made
of iron and nickel at a temperature of 5 100 C. Around this is
a hot liquid mantle made up of water, ammonia and methane
which generates electrical currents and a magnetic field. The
outer atmosphere layer is made up of 80% hydrogen gas,
19% helium gas and 1 % methane gas (which gives the planet
its blue colour).
Neptune Atmosphere : More Stormy than Uranus
The atmosphere of Neptune is more active than Uranus with
many storms and a very large one, the Great Dark Spot,
similar to Jupiter’s large red storm. Cloud winds of 2 100
km/h have been observed.
Neptune Magnetosphere
Neptune’s magnetosphere deflects solar wind particles past
the planet.
Neptune
Rings
Neptune
has dark,
thin rings
made up of
ices and
dust.
Neptune Moons
Twelve moons have been discovered orbiting Neptune.
Triton is the largest and most geologically active moon of
Neptune. It shows cracks and nitrogen geysers erupting.
The Kuiper Belt : 30 – 55 AU from the Sun
The Kuiper Belt is a flat disc of millions of small bodies that is
orbiting the sun beyond the orbit of Neptune. These bodies are
thought to be the remains of the formation of our Solar System
The Kuiper belt is like the asteroid belt but Kuiper Belt bodies
are more ice-like whereas asteroids are more stony or metallic.
The Kuiper Belt
Some of the objects in the Kuiper Belt are called dwarf planets
and even have moons that orbit them. Pluto is a Kuiper Belt
Dwarf Planet.
The Kuiper Belt
Occasionally objects from the Kuiper Belt move into the Solar
System. Some of the moons of planets (Neptune’s moon
Triton and Saturn’s moon Phoebe) are thought to be Kuiper
Belt objects that were captured by the planets.
The Oort Cloud
The Oort
Cloud is a
threedimensional
cloud of icy
fragments
and debris
that lies
around and
beyond the
Kuiper Belt.
Distance of the Oort Cloud
The Oort Cloud is from 2000 – 100 000 AU away from the sun,
about ¼ the distance to the star, Proxima Centauri, the star
nearest our Sun.
The Oort Cloud and Kuiper Belt : Home of Comets
Comets are thought to come from either the Oort Cloud or the
Kuiper Belt. The Gas Giant planets’ gravity affects objects in
the Kuiper Belt and the Oort cloud, sending them into our
Solar System towards the Sun.
Comets
Comets were once referred to as “dirty snowballs”. Comets
are composed of ices, rocks and gases. Comets originate in
the Kuiper Belt or the Oort Cloud. Through collisions with
other objects, they may get “bumped” into our Solar System
or they may be pulled by the gravity of the gas giants into our
Solar System.
Comets Captured by the Sun’s Gravity
As comets move into our Solar System, they are attracted by
the Sun’s gravity since the sun has a mass that is 99.89% of
our whole solar system.
Comets have “Tails”
As comets move towards the sun, the radiation of the sun
and solar wind particles start to strip away parts of the icy
comet which creates a tail that points away from the Sun.
Comets often Reappear
Most comets take up orbits that cause them to return around
the Sun. If comets take less than 200 years to reappear they
are called short term comets and from 200 to thousands or
millions of years to reappear are called long term comets.
A Comet’s Appearance in the Sky
Comets often Reappear
Halley’s Comet is a famous short term comet that comes
every 74 to 75 years. It was last seen in 1986. It has been
observed since 250 BC but persons did not realize that it was
the same comet. Historically, comets have been thought to
be omens of disaster and generated fear in people whenever
they were seen.
Halley’s Comet and the English Disaster
Hailey’s comet was seen the year that William the Conqueror
from France invaded England. The English King Harold was
killed in battle by an arrow going into his eye.
Halley’s Comet and the English Disaster
William took care of Harold for some time in France and
Harold swore an oath of loyalty to William. When the English
king died, William had a claim to the throne that Harold then
rejected which caused the French invasion.