Transcript What do you know about light?

Planets
What we know…
• There are eight planets in our solar
system:
– Mercury, Venus, Earth, Mars, Jupiter,
Saturn, Uranus, and Neptune.
• The planets are arranged into inner
and outer planets based on their
distances from the sun.
• Brain Pop Our Solar System:
• http://www.brainpop.com/science/s
pace/solarsystem/
Pluto; Not a Planet anymore…
• Pluto was once considered to be a planet
in our solar system.
• Due to advances in technology
Astronomers located other objects
further out than the orbit of Pluto that
were the same size, or even bigger.
• This forced the IAU to reconsider the
criteria required for planet status.
What makes a Planet a Planet?
• A planet must meet the following 3
requirements in order to qualify as a
planet:
– It needs to be in orbit around the Sun
– It needs to have enough gravity to pull itself
into a spherical shape
– It needs to have “cleared the neighborhood”
of its orbit
What does “cleared the
neighbourhood” mean?
• As planets form, they become the
dominant gravitational body in their orbit
in the Solar System.
• As they interact with other, smaller
objects, they either consume them, or
sling them away with their gravity.
Poor Pluto…
• With the discovery of other, larger,
objects in it’s orbit Pluto was
reconsidered and became known as
a dwarf planet.
• http://www.brainpop.com/science/s
pace/pluto/
What Else is Out There?
• Asteroids: Rocks floating in space. These can
range in size from 1m to hundreds of km.
• Thought to be the building blocks of our solar
system, many share characteristics of planets.
• Some asteroids cross the path of Earth and
pose a potential collision hazard.
• http://www.brainpop.com/science/space/asteroi
ds/
Comets
• Comets are made up of ice and dust and orbit
the sun at large distances.
• At specific times certain comets are visible to
the human eye, the most famous being Halley’s
comet.
• http://www.youtube.com/watch?v=C8zV1xiGqf4
• http://www.youtube.com/watch?v=WUzn_BtldU
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Meteors
• As rocks and fragments from space enter
to the Earth’s atmosphere friction
causes these particles to burn up.
• If the fragment is large enough it
sometimes generates enough light to be
visible, often be called “shooting stars”,
these are called Meteors.
Meteorites
• When meteors are large enough or
tough enough where a part of it
survives to strike the Earth they are
called Meteorites.
• http://www.youtube.com/watch?v=SMnZr5
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Questions 
1.
Explain how the inner planets are different from the
outer planets.
2.
In what way is Uranus different from the other planets?
3.
Explain why Pluto is not considered a planet anymore.
4.
Explain how comets, asteroids and meteors are
different.
5.
Neptune is sometimes farther from the sun than Pluto.
Explain why this happens.