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Bellwork Review Questions: Ch 4
1. What is a planet and how is it formed? (think of
the video we watched “How Universe was Made”)
2. How do we know how the solar system formed?
3. What does an astronomical unit measure?
4. Why is Pluto now considered a Dwarf Planet?
The Moon
A look at our nearest
neighbor in Space!
LESSON 2
Free powerpoints at http://www.worldofteaching.com
What is the Moon?
• A natural satellite
• One of more than 96 moons in
our Solar System
• The only moon of the planet
Earth
Location, location, location!
• About 384,000 km
(240,000 miles)
from Earth
• 3,468 km (2,155
miles) in diameter
(about ¼ the size of
Earth)
The Moon’s Surface
• No atmosphere
• No liquid water
• Extreme
temperatures
– Daytime = 130C
(265°F)
– Nighttime = -190C
(-310 F)
• 1/6 Earth’s gravity
Lunar Features - Highlands
• Mountains up to 7500 m
(25,000 ft) tall
• Rilles (trenchlike
valleys)
Lunar Features - Craters
• Up to 2500 km (1,553 miles) across
• Most formed by meteorite impact on the Moon
• Some formed by volcanic action inside the Moon
Lunar Features - Maria
• Originally thought to be
“seas” by early
astronomers
• Darkest parts of lunar
landscape
• Filled by lava after crash
of huge meteorites on
lunar surface 3-4 billion
years ago
• Mostly basalt rock
Craters
Can you see the rays?
Maria
Does this photo show
us a limb or terminator
line?
Movements of the Moon
• Revolution – Moon orbits
the Earth every 271/3 days
• The moon rises in the east
and sets in the west
• The moon rises and sets
50 minutes later each day
• Rotation – Moon turns on
its axis every 27 days
• Same side of Moon
always faces Earth
Craters
Name these
features.
Maria
Name
these
features.
Kuiper Belt
_______________
Oort Cloud
National Aeronautics and
Educational Product
Space Administration
Teachers Grades 5-12
Exploring Meteorite Mysteries
Slide Set with Script
Larger meteorites
are extremely rare, but
make enormous
craters when they hit
the Earth
It was formed about
50,000 years ago when
a large iron meteorite
hit the Earth
Scientists estimate
that the meteorite
weighed one million
tons
Meteor Crater in Arizona is over
one kilometer across and 150
meters deep
Although people have
seen meteorites fall since
the earliest times, it was
only about 1800 when
scientists finally became
convinced that rocks really
did fall from the sky
Since then, we've
discovered that most
meteorites come from the
asteroid belt, the area of
the solar system between
the orbits of Mars and
Jupiter where many
asteroids orbit the sun
Asteroids are small planets,
fragments of rock and iron left
over from the formation of the
solar system or the breakup of
larger fragments

Many asteroids probably
look like Ida, the asteroid in
this picture taken by the
Galileo spacecraft in 1993
Ida is about 30 kilometers
long, is made of rock, and has
many craters
Comets are small bodies
made of rock, dust and ice,
formed in the distant reaches
of the solar system
Then solar radiation heats the
comet's surface, causing part
of the ice to boil off into space
and carry some of the dust
with it
When this happens the comet
can develop a "tail" millions of
kilometers long, and leave a
dust trail behind in solar orbit
Formation of the Solar System
It began with a Nebular
Gas Cloud
From which developed Proto-Sun & Planets
From which came the Sun, Planets, & Debris
Which finally cleared out to leave just the Sun & Planets (and
their moons, etc.)
Rocky Matter
(Source of craters)
Debris
Icy Matter (Source of
comets)
Icy Matter ...
Jan Oort’s Cometary Cloud
Most comets that we see today are believed to
have come from the Oort cloud.
Why do you suppose they leave the cloud in the
first place?
Coma May be
1000’s of
km
Nucleus - Few 10’s of
km
The Head of a Comet
The Tail of a Comet
Larger
meteorit
es
don't
come
from
comets
but from
asteroid
It's a
long
way
from the
asteroid
belt to
the
Earth
Very few asteroid pieces get the chance to travel
that
far
Most asteroids never do, and spend eternity in space,
Every now and again the orbits of
asteroids cross and their quiet times
end
Then the asteroids collide and
shatter, and the pieces fly into
different orbits around the sun
Eventually some of their orbits
cross the Earth's orbit, and the
piece of asteroid can hit the Earth
Some of these pieces orbit closer
and closer to the sun
We see this moving flame as
a meteor crossing the sky
If the asteroid fragment is big
enough, fist-sized or so, it
won't burn up completely and
will fall to the Earth as a
meteorite
These small meteorites do
not explode or make craters
when they hit
They just hit like an extra
large hailstone or a rock
thrown from across the street
Meteorites have also had devastating
effects on life...
The dinosaurs were killed
65 million years ago after a
huge meteorite hit the Earth
The explosion caused great
storms and waves, and the
sky was dark for months
with dust and ash
The dinosaurs, along with
many other animals and
plants, were probably killed
by the climate changes that
followed the explosion
Inner Planets
Outer Planets
What are rings?
What is an orbit?
Describe the shape of an orbit.