Download The Solar System

The Solar System
What is a planet?
Old Definition
a large, solid body that shines by reflecting
sunlight and revolves in a stable orbit
around the Sun
What is a planet?
New Definition
3 major criteria are required to classify an
object as a planet:
– a large solid body that shines by reflecting
sunlight and revolves in a stable orbit around
the sun
– large enough that its own gravity pulls it into a
round shape
– large enough to clear the path of its orbit
Classifying Planets
Inner Planets are
between the Sun and
the Asteroid Belt. They
are inside the belt.
Outer Planets are
farther from the Sun.
They are outside the
Asteroid Belt.
The Asteroid Belt is
between Mars and
Jupiter.
Inner Planets
• Which planets are the inner planets?
Inner Planets
• Which ones are the inner planets?
– Mercury, Venus, Earth, Mars
• Inner planets are also called terrestrial
planets. Why?
Inner Planets
• Which ones are the inner planets?
– Mercury, Venus, Earth, Mars
• Inner planets are also called terrestrial
planets. Why?
– made mainly of rock
Mercury
Mercury has almost no gravity so it cannot hold on to
an atmosphere. Without an atmosphere and being
close to the sun causes temperatures to be very high
during the day and very low at night.
Venus
Called Earth’s twin
because they have
similar gravity, mass,
and are close to one
another.
Because of its thick
atmosphere, a lot of
heat is trapped, making
the planet very hot.
Earth
Mars is red because
there is a substance
called iron oxide in
the soil. The largest
volcano in the solar
system is on Mars.
Mars was named
after the god of war.
The names of its two
moons, Phobos and
Deimos, mean panic
and fear.
Currently there are
several satellites in
orbit around Mars
Crewed missions to
Mars are planned.
Mars
The Asteroid Belt separates the
Inner and the Outer Planets.
Asteroid belt
• between Mars and
Jupiter
• consists of thousands
of rock fragments in
orbit around the Sun
• largest asteroids have
been reclassified as
dwarf planets
Many objects in the Asteroid Belt
have names.
Asteroid Belt
The Outer Planets are outside of
the Asteroid Belt.
↓
Outer planets
• Which planets are
included in the outer
planets?
– Jupiter, Saturn,
Uranus, Neptune
• made mostly of frozen
hydrogen and helium
• atmospheres can be
made of thick layers
of gas
Outer planets
• also known as Gas
Giants or Jovian
Planets
• known to have a lot
of moons due to
large mass and
gravitational pull
Jupiter
largest planet in the
solar system
Gives out more
heat into space
than it receives
from the sun
has spots
takes 30 years
to complete
one orbit
around the sun
lowest density
of any planet;
its density is
lower than that
of water!
Gives out more
heat than it
receives
Saturn
Uranus – rotates on its side
has a blue color due to
a substance called
methane gas in its
atmosphere
so far from the sun that
its temperature is -348
degrees Fahreneheit
has 42 years of dark
winter followed by 42
years of constant
summer
Neptune
discovered
mathematically
has winds of
2000
kilometers per
hour
Voyager 1
launched in 1977
finished a survey
of outer planets
in 1989
uses radioactive
power packs
travels at 17 km/s
its radio message
takes 16 hours to
reach Earth
Pluto
Dwarf Planet
In 2006 Pluto was
reclassified as a Dwarf
Planet. To be a Dwarf
Planet, an object has to be
round and orbit the sun,
not be a moon, and not
able to clear the path of its
orbit.
Pluto is very different from
the outer planets. It is
much smaller and it is
more like a terrestrial
planet than a gas giant.
Pluto has three moons,
Charon, Nix and Hydra.
Pluto is not a planet anymore!
• Pluto’s orbit is
not considered
stable.
• It crosses
Neptune’s
orbit.
Kuiper Belt
↓
Pluto is not a planet anymore.
It is part of the Kuiper Belt.
• The Kuiper Belt is a region of debris 4.5 to
7.5 billion km (2.8 billion to 4.6 billion miles)
from the sun.
• The Kuiper Belt is 30 to 50 Astronomical
Units (AU) from the sun. One AU is the
distance from the Sun to Earth.
• Pluto is a Kuiper Belt Object or KBO.
• So far 1300 objects in this belt have been
identified. Pluto and three others are
considered dwarf planets. There may be as
many as 70,000 objects in the belt!