Download The Planets

The Planets
7.3
What are some of the objects that
make up our solar system?
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Planets
Moons
The Sun
Comets
Asteroids
Stars
What is the center of the solar system?
The Sun
The Solar System
• What is the Solar System?
• The solar system is the Sun and all the objects
that orbit around the Sun.
• What is a planet?
• A planet is a large object orbiting a star.
Our Solar System
• Our solar system is made up of 8
planets orbiting the Sun.
What is a moon?
• A moon is a natural object that orbits a planet.
In our solar system all but 2 planets
have one or more moons.
Planets
• The planets in our solar system
travel in an elliptical orbits
around the Sun.
Planets in our solar system in order
(nearest to the Sun to farthest away)
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Mercury
Venus
Earth
Mars
Jupiter
Saturn
Uranus
Neptune
Other objects in space
• Comets
• Asteroids
• Meteors
Comets
• A comet is a mixture
of frozen gases, ice,
dust, and rock that
moves in an elliptical
orbit around the
Sun.
Asteroids
• An asteroid is a rock
that revolves around
the Sun. Most are
located between Mars
and Jupiter in the
asteroid belt.
• Sizes of asteroids vary.
They can be less than 1
mile wide or as big as
500 miles wide!
Meteoroids
• Meteoroids are small objects in space. Objects
that cross paths with Earth and enters Earth’s
atmosphere is called a meteor.
• Most of these objects, meteors, burn up as
they travel through Earth’s atmosphere.
• The meteors that do make through Earth’s
atmosphere and land on the ground are called
meteorite.
Inner Planets
• The inner planets are closer to
the Sun than the asteroid belt.
• They are Mercury, Venus,
Earth, and Mars.
• Common characteristics of
inner planets:
– Surfaces made of rock
– Their orbits are spaced close
together.
– Few or no moons
– No rings
Which planet is closest to the Sun?
• Mercury
• How many moons do each of the inner
planets have?
• Mercury- 0
• Venus- 0
• Earth- 1
• Mars- 2
Outer Planets
• 4 outer planets located beyond the asteroid belt.
• Jupiter, Saturn, Uranus, and Neptune
• Common characteristics:
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Made mostly of gas and sometimes called gas planets
Metallic core and thick atmosphere
Orbits are spaced far apart.
All have rings and many moons.
Days are very short and they spin rapidly on their
axes.
How do the outer planets differ in size
from the inner planets?
• The outer planets are much
larger than the inner planets.
Why are the outer planets called gas
planets?
• The outer planets are made of various
gases, not rock.
What is a moon?
• A moon is a natural
object that orbits a
planet.
• Different planets have
different numbers and
sizes of moons.
• Inner planets have
fewer moons than the
outer planets.
Satellite
• A satellite is an object in
space that circles around
another object.
• Moons are natural satellites.
• People put artificial satellites
in space. Some of these are
weather and
communications satellites
and space probes.
Sizes of Moons
• The sizes vary.
• The largest moon in the solar system is
Jupiter’s Ganymede. It is larger than Pluto and
Mercury.
• Earth’s moon is also larger than Pluto.
Craters
• When small objects in space
collide with large objects
craters form on the larger
surface.
• A crater is a bowl-shaped
hole.
• Earth’s moon craters can be
seen from Earth.
Exploration of our Solar System
• All the planets in our solar system have been
explored using space probes.
• A space probe is a vehicle carrying
instruments that is sent to explore objects in
space.
Moon Exploration
• In 1969 the United States sent the first
astronauts to the Moon. The Moon is the only
place in space that astronauts have explored.
Exploring Mars
• Two rovers, Spirit and
Opportunity, were placed on
Mars in 2004.
• Rovers are small robot cars.
• These rovers were equipped
with cameras and took
pictures of soil, pebbles, and
rocks. Instruments on the
rover found evidence that
liquid water may have once
existed on Mars.
Space probe is on it’s way to Pluto!
• A space probe, New Horizons, was launched in
January 2006 heading for Pluto.
• The probe is planned to land on Pluto in 2015.
Review Time!!!
• If scientists found a natural object
moving around a planet, what
would they call it?
• Since this natural object is
moving around a planet,
scientists will most likely call it a
moon.
Other than planets, what other objects
are in a solar system?
• Stars, moons, asteroids,
meteoroids, and comets.
If you went on Venus, in what direction would
you see the Sun rise and set?
• Venus rotates in the opposite direction from
earth. On Venus, if you could see the Sun
through its thick clouds, the Sun would appear
to rise in the west and set in the east.
How are the inner planets alike? How
are they different?
• The planets all have
surfaces made of rock.
• They vary in size.
If scientists discover a new planet that appears
to be the same color as Uranus, what can you
infer about its atmosphere?
• The methane in Uranus’ atmosphere
causes the planet to have a blue
appearance. If a newly discovered
planet has a blue appearance, you
could infer that this planet also
contains methane in its atmosphere.
Name one way Saturn differs from
other planets.
• Saturn’s rings are more noticeable
than the other planets’.
• Saturn is smaller than Jupiter, but
larger than Uranus and Neptune.
How are a moon and an artificial
satellite different?
• A moon is a natural object that
orbits a planet. An artificial
satellite also orbits a planet,
but it was put in to space by
humans.
What happens when objects in space
collide with Earth?
• Smaller objects burn up in
Earth’s atmosphere. Larger
objects reach the ground and
form craters.
What might be inferred from the discovery that
liquid water may once have existed on Mars?
• As far as we know, liquid water
must be present for life to
exist. The discovery of liquid
water on Mars means that life
may have existed on Mars at
one time.